The document discusses several key object-oriented programming concepts including:
- Different types of SQL joins like inner, left, right, full outer, and left outer joins.
- The static keyword in PHP and how it allows properties and methods to be accessed without object instantiation.
- Visibility levels like public, private, and protected for class properties and methods.
- Abstract classes and interfaces, how they are similar but interfaces define contracts while abstract classes can contain partial implementations.
- The difference between exceptions which are thrown intentionally and errors which occur unintentionally.
- The difference between passing arguments by value which passes a copy versus by reference which passes a reference to the original variable.
Adapter classes provide default implementations of listener interface methods to avoid implementing unused methods. The WindowAdapter class is an adapter for the WindowListener interface. It implements empty method bodies for the WindowListener's seven abstract methods. This allows classes to extend WindowAdapter and only override the needed methods rather than all methods of the WindowListener interface. Adapters exist for convenience by providing listener object implementations with default empty method bodies.
The document discusses interfaces in C#, including how they define method signatures without implementations, how classes can implement multiple interfaces, and how interfaces can inherit from other interfaces. It provides an example of a class implementing two interfaces, including using explicit interface implementation when a method signature is shared between interfaces. The document emphasizes that interfaces allow for loosely coupled systems by separating method definitions from implementations.
Indus Valley Partner aptitude questions and answersSushant Choudhary
This document contains several code snippets and questions about Java programming concepts like arrays, exceptions, interfaces, and access modifiers. The correct answers and explanations provided indicate that:
1) Option B is the only valid way to declare and initialize an array with multiple elements in one statement.
2) Interface methods can only use the public access modifier and cannot be static, final, private, protected, transient, volatile, or synchronized.
3) The default values for array elements of primitive types are 0 for int, 0.0f for float, and null for reference types like String. For non-primitive types like Dog, the default is also null.
Interfaces are reference types that define a contract that other classes can implement. Interfaces cannot contain fields or constructors, and all members are implicitly public and abstract. A class can implement multiple interfaces, allowing it to inherit functionality from different sources, while only being able to inherit from one base class. Explicit interface implementation allows a class to implement the same method signature defined in multiple interfaces to avoid name collisions.
The document provides an overview of object-oriented programming in PHP 5. It discusses key OOP concepts like classes, inheritance, properties, methods, abstraction, interfaces, traits, overloading, and iteration. New features in PHP 5 like visibility, abstract classes, interfaces, cloning and type hinting are also covered at a high level. The document is intended to introduce developers to OOP in PHP 5.
Slides: http://pa4373.github.io/jstutorials_corepart/
GitHub Repo: https://github.com/pa4373/jstutorials_corepart
This is the first part of JavaScript programming tutorials. This tutorial introduces the brief history of JavaScript, the relationship of the specification and a variety of implementations, and then the basic syntax and the concepts are introduced, that can be generally applied to programming interactions with different runtimes.
Generic Types in Java (for ArtClub @ArtBrains Software)Andrew Petryk
This document discusses generics in Java. It provides an overview of generics, including:
- How generics allow for stronger type checking and elimination of casts compared to non-generic code.
- The benefits of generics include type safety and implementation of generic algorithms.
- Key concepts related to generics include type erasure, bounds/restrictions, wildcards, and type inference.
- Examples are provided to illustrate generic classes, methods, and common issues like heap pollution.
Control structures functions and modules in python programmingSrinivas Narasegouda
The document discusses control structures, functions, modules, and Python's standard library. It covers topics like conditional branching, looping, functions, modules, packages, exceptions, strings, and more. Custom functions in Python include global functions, local functions, lambda functions, and methods. Modules allow packaging functionality and importing it into other code.
Adapter classes provide default implementations of listener interface methods to avoid implementing unused methods. The WindowAdapter class is an adapter for the WindowListener interface. It implements empty method bodies for the WindowListener's seven abstract methods. This allows classes to extend WindowAdapter and only override the needed methods rather than all methods of the WindowListener interface. Adapters exist for convenience by providing listener object implementations with default empty method bodies.
The document discusses interfaces in C#, including how they define method signatures without implementations, how classes can implement multiple interfaces, and how interfaces can inherit from other interfaces. It provides an example of a class implementing two interfaces, including using explicit interface implementation when a method signature is shared between interfaces. The document emphasizes that interfaces allow for loosely coupled systems by separating method definitions from implementations.
Indus Valley Partner aptitude questions and answersSushant Choudhary
This document contains several code snippets and questions about Java programming concepts like arrays, exceptions, interfaces, and access modifiers. The correct answers and explanations provided indicate that:
1) Option B is the only valid way to declare and initialize an array with multiple elements in one statement.
2) Interface methods can only use the public access modifier and cannot be static, final, private, protected, transient, volatile, or synchronized.
3) The default values for array elements of primitive types are 0 for int, 0.0f for float, and null for reference types like String. For non-primitive types like Dog, the default is also null.
Interfaces are reference types that define a contract that other classes can implement. Interfaces cannot contain fields or constructors, and all members are implicitly public and abstract. A class can implement multiple interfaces, allowing it to inherit functionality from different sources, while only being able to inherit from one base class. Explicit interface implementation allows a class to implement the same method signature defined in multiple interfaces to avoid name collisions.
The document provides an overview of object-oriented programming in PHP 5. It discusses key OOP concepts like classes, inheritance, properties, methods, abstraction, interfaces, traits, overloading, and iteration. New features in PHP 5 like visibility, abstract classes, interfaces, cloning and type hinting are also covered at a high level. The document is intended to introduce developers to OOP in PHP 5.
Slides: http://pa4373.github.io/jstutorials_corepart/
GitHub Repo: https://github.com/pa4373/jstutorials_corepart
This is the first part of JavaScript programming tutorials. This tutorial introduces the brief history of JavaScript, the relationship of the specification and a variety of implementations, and then the basic syntax and the concepts are introduced, that can be generally applied to programming interactions with different runtimes.
Generic Types in Java (for ArtClub @ArtBrains Software)Andrew Petryk
This document discusses generics in Java. It provides an overview of generics, including:
- How generics allow for stronger type checking and elimination of casts compared to non-generic code.
- The benefits of generics include type safety and implementation of generic algorithms.
- Key concepts related to generics include type erasure, bounds/restrictions, wildcards, and type inference.
- Examples are provided to illustrate generic classes, methods, and common issues like heap pollution.
Control structures functions and modules in python programmingSrinivas Narasegouda
The document discusses control structures, functions, modules, and Python's standard library. It covers topics like conditional branching, looping, functions, modules, packages, exceptions, strings, and more. Custom functions in Python include global functions, local functions, lambda functions, and methods. Modules allow packaging functionality and importing it into other code.
This document provides an overview of object-oriented programming concepts in C++, including definitions of objects, classes, tokens, keywords, identifiers, constants, variables, operators, control structures, and functions. It explains that an object is an instance of a class, and discusses the main components of a class like data and functions. It also describes different types of tokens, operators, control structures like if/else, switch, while, do-while and for loops, and the syntax of defining functions in C++.
Interfaces in Java declare methods but do not provide method implementations. A class can implement multiple interfaces but extend only one class. Interfaces are used to define common behaviors for unrelated classes and allow classes to assume multiple roles. Nested interfaces group related interfaces and must be accessed through the outer interface or class.
This document compares and contrasts abstract classes and interfaces in Java. It defines abstract classes as partially abstract reusable code that can contain both abstract and concrete methods, while interfaces are fully abstract reusable contracts that can only contain abstract methods. The document provides examples of abstract class and interface syntax and usage, highlighting that abstract classes can have constructors and non-public members while interfaces cannot. It concludes that abstract classes are not completely abstract but interfaces are.
The document discusses exception handling in PL/SQL. It defines exceptions as abnormal conditions that can occur during program execution. There are two types of exceptions: system-defined exceptions which are predefined by Oracle and user-defined exceptions which are declared by the user. The document provides examples of how to handle different system-defined exceptions like NO_DATA_FOUND, INVALID_CURSOR, CURSOR_ALREADY_OPENED, INVALID_NUMBER, and ZERO_DIVIDE. It also demonstrates how to declare and raise user-defined exceptions. The RAISE_APPLICATION_ERROR technique to specify custom error numbers and messages without an exception block is also covered.
This document discusses cursors in PL/SQL. It defines a cursor as a pointer that is used to point to individual rows in a database table. It explains that there are two types of cursors: implicit cursors and explicit cursors. Implicit cursors are used automatically for SQL statements and have attributes like %FOUND and %ROWCOUNT to check the status of DML operations. Explicit cursors must be declared, opened, values fetched from them into variables, and then closed to access multiple rows from a table in a controlled manner using PL/SQL.
Notes of Important Programming Fundamental QuestionsAdeel Rasheed
A function is a named block of code that performs a specific task. The function header contains the return type, name, and parameters. The function body contains the code that is executed when the function is called. Functions make code reusable and easier to maintain. Variables declared inside a function are local and can only be accessed within the function. Variables declared outside functions are global and can be accessed throughout the program. Arrays store multiple values of the same type and allow accessing elements via an index. One-dimensional arrays use a single index while two-dimensional arrays use two indexes.
Templates and Exception Handling in C++Nimrita Koul
This document discusses templates and exception handling in C++. It provides an overview of templates, including why they are used for generic programming and how to define function and class templates. Exception handling in C++ uses try, catch, and throw blocks. The try block contains code that may throw exceptions, catch blocks handle specific exceptions, and throw explicitly throws an exception. The document contains examples of templates, exception handling, and derived class exceptions. It also discusses opportunities available at the School of CIT at Reva University.
This chapter discusses control structures in Java programs. It covers relational operators and logical expressions used for comparisons. Selection control structures like if, if-else, and switch statements are examined along with examples. The chapter also provides an example programming problem on cable company billing that demonstrates using control structures and nested conditional logic.
This document discusses stacks and queues as data structures. It begins by describing stacks as having a last-in, first-out characteristic and common uses like method call order tracking. It then provides examples of implementing a stack using an array and manipulating elements by pushing and popping. The document also covers queues as having a first-in, first-out characteristic like a waiting line. It proposes a Queue interface and discusses challenges of array-based implementations versus using Java's LinkedList class.
When passing primitive variables into methods, the value is passed by value rather than by reference. This means that changes to the parameter inside the method do not affect the original variable. For reference types, the reference itself is passed by value but it still points to the same object, so changes to the object's content would be visible outside the method.
1. C++ introduces three access modifiers - public, private, and protected - to control access to members of a class and establish boundaries in the relationship between a class and its clients.
2. Public members form the class's interface and are accessible by anyone. Private members are the internal workings of the class and are inaccessible to clients. Protected members are accessible by derived classes.
3. The 'friend' keyword allows specific functions or classes to access a class's private and protected members, but friendship is not inherited and overuse of friends is not recommended.
This document discusses the different types of tokens in Java including keywords, identifiers, literals, operators, and separators. It provides examples and details for each token type. Keywords such as if, else, class cannot be used as identifiers. Identifiers name variables and follow naming rules. Literals represent fixed values like integers and strings. Operators perform operations on operands like addition and comparison. Separators include braces, brackets, parentheses and terminators used in code blocks and expressions.
The document provides information about Java programming concepts including:
- How to download, install Java, and write a simple "Hello World" program.
- Common operators in Java like arithmetic, assignment, logical, and comparison operators.
- How to compile and run a Java program from the command line.
- Core Java concepts like variables, data types, classes, and methods.
- The document is intended as an introduction to Java programming for beginners.
The document discusses object oriented programming concepts related to exception handling in Java. It covers the benefits of exception handling such as separating error handling code from regular logic and propagating errors up the call stack. It also describes key exception handling constructs like try, catch, throw and throws. The different exception models of termination and resumption are explained along with the exception hierarchy in Java.
Abstract Class & Abstract Method in Core JavaMOHIT AGARWAL
This document discusses abstract classes in Java. It defines an abstract class as a class declared with the abstract keyword that may contain abstract and non-abstract methods. Abstract classes cannot be instantiated and require subclasses to implement any abstract methods. The document provides examples of abstract class and method declarations and demonstrates how subclasses must implement abstract methods to be instantiated. It also outlines some key uses of abstract classes such as code sharing among related classes.
This document outlines Chapter 4 of a textbook on control structures in programming. It introduces algorithms and pseudocode, then covers various control structures like sequence, selection, and repetition structures. It discusses if, if/else, and while statements in Java. It includes examples of algorithms to calculate class averages using counter-controlled and sentinel-controlled repetition. It also covers topics like compound assignment operators, increment/decrement operators, and nested control structures.
Loops allow blocks of code to be repeatedly executed. The three types of loops in C are while loops, for loops, and do-while loops. While loops check the condition before each iteration. For loops allow initialization, condition checking, and increment/decrement in the loop header. Do-while loops check the condition after executing the block at least once. Break and continue statements can be used to exit or skip portions of loops. Switch statements compare a value to multiple case values and execute the corresponding block.
GCG is an elite insurance and financial services firm that has been in business for 35 years. It offers a wide range of employee benefit programs and consulting services. GCG works with over 250 producers and employees to create long-term benefit plans and has a strategic relationship with Milliman, one of the largest actuarial firms. GCG provides clients with property and casualty insurance, employee benefits, retirement plans, executive benefits, and consulting services. It also offers resources like online tools, communications support, and benchmarking surveys to help clients manage their benefits.
This document provides an overview of object-oriented programming concepts in C++, including definitions of objects, classes, tokens, keywords, identifiers, constants, variables, operators, control structures, and functions. It explains that an object is an instance of a class, and discusses the main components of a class like data and functions. It also describes different types of tokens, operators, control structures like if/else, switch, while, do-while and for loops, and the syntax of defining functions in C++.
Interfaces in Java declare methods but do not provide method implementations. A class can implement multiple interfaces but extend only one class. Interfaces are used to define common behaviors for unrelated classes and allow classes to assume multiple roles. Nested interfaces group related interfaces and must be accessed through the outer interface or class.
This document compares and contrasts abstract classes and interfaces in Java. It defines abstract classes as partially abstract reusable code that can contain both abstract and concrete methods, while interfaces are fully abstract reusable contracts that can only contain abstract methods. The document provides examples of abstract class and interface syntax and usage, highlighting that abstract classes can have constructors and non-public members while interfaces cannot. It concludes that abstract classes are not completely abstract but interfaces are.
The document discusses exception handling in PL/SQL. It defines exceptions as abnormal conditions that can occur during program execution. There are two types of exceptions: system-defined exceptions which are predefined by Oracle and user-defined exceptions which are declared by the user. The document provides examples of how to handle different system-defined exceptions like NO_DATA_FOUND, INVALID_CURSOR, CURSOR_ALREADY_OPENED, INVALID_NUMBER, and ZERO_DIVIDE. It also demonstrates how to declare and raise user-defined exceptions. The RAISE_APPLICATION_ERROR technique to specify custom error numbers and messages without an exception block is also covered.
This document discusses cursors in PL/SQL. It defines a cursor as a pointer that is used to point to individual rows in a database table. It explains that there are two types of cursors: implicit cursors and explicit cursors. Implicit cursors are used automatically for SQL statements and have attributes like %FOUND and %ROWCOUNT to check the status of DML operations. Explicit cursors must be declared, opened, values fetched from them into variables, and then closed to access multiple rows from a table in a controlled manner using PL/SQL.
Notes of Important Programming Fundamental QuestionsAdeel Rasheed
A function is a named block of code that performs a specific task. The function header contains the return type, name, and parameters. The function body contains the code that is executed when the function is called. Functions make code reusable and easier to maintain. Variables declared inside a function are local and can only be accessed within the function. Variables declared outside functions are global and can be accessed throughout the program. Arrays store multiple values of the same type and allow accessing elements via an index. One-dimensional arrays use a single index while two-dimensional arrays use two indexes.
Templates and Exception Handling in C++Nimrita Koul
This document discusses templates and exception handling in C++. It provides an overview of templates, including why they are used for generic programming and how to define function and class templates. Exception handling in C++ uses try, catch, and throw blocks. The try block contains code that may throw exceptions, catch blocks handle specific exceptions, and throw explicitly throws an exception. The document contains examples of templates, exception handling, and derived class exceptions. It also discusses opportunities available at the School of CIT at Reva University.
This chapter discusses control structures in Java programs. It covers relational operators and logical expressions used for comparisons. Selection control structures like if, if-else, and switch statements are examined along with examples. The chapter also provides an example programming problem on cable company billing that demonstrates using control structures and nested conditional logic.
This document discusses stacks and queues as data structures. It begins by describing stacks as having a last-in, first-out characteristic and common uses like method call order tracking. It then provides examples of implementing a stack using an array and manipulating elements by pushing and popping. The document also covers queues as having a first-in, first-out characteristic like a waiting line. It proposes a Queue interface and discusses challenges of array-based implementations versus using Java's LinkedList class.
When passing primitive variables into methods, the value is passed by value rather than by reference. This means that changes to the parameter inside the method do not affect the original variable. For reference types, the reference itself is passed by value but it still points to the same object, so changes to the object's content would be visible outside the method.
1. C++ introduces three access modifiers - public, private, and protected - to control access to members of a class and establish boundaries in the relationship between a class and its clients.
2. Public members form the class's interface and are accessible by anyone. Private members are the internal workings of the class and are inaccessible to clients. Protected members are accessible by derived classes.
3. The 'friend' keyword allows specific functions or classes to access a class's private and protected members, but friendship is not inherited and overuse of friends is not recommended.
This document discusses the different types of tokens in Java including keywords, identifiers, literals, operators, and separators. It provides examples and details for each token type. Keywords such as if, else, class cannot be used as identifiers. Identifiers name variables and follow naming rules. Literals represent fixed values like integers and strings. Operators perform operations on operands like addition and comparison. Separators include braces, brackets, parentheses and terminators used in code blocks and expressions.
The document provides information about Java programming concepts including:
- How to download, install Java, and write a simple "Hello World" program.
- Common operators in Java like arithmetic, assignment, logical, and comparison operators.
- How to compile and run a Java program from the command line.
- Core Java concepts like variables, data types, classes, and methods.
- The document is intended as an introduction to Java programming for beginners.
The document discusses object oriented programming concepts related to exception handling in Java. It covers the benefits of exception handling such as separating error handling code from regular logic and propagating errors up the call stack. It also describes key exception handling constructs like try, catch, throw and throws. The different exception models of termination and resumption are explained along with the exception hierarchy in Java.
Abstract Class & Abstract Method in Core JavaMOHIT AGARWAL
This document discusses abstract classes in Java. It defines an abstract class as a class declared with the abstract keyword that may contain abstract and non-abstract methods. Abstract classes cannot be instantiated and require subclasses to implement any abstract methods. The document provides examples of abstract class and method declarations and demonstrates how subclasses must implement abstract methods to be instantiated. It also outlines some key uses of abstract classes such as code sharing among related classes.
This document outlines Chapter 4 of a textbook on control structures in programming. It introduces algorithms and pseudocode, then covers various control structures like sequence, selection, and repetition structures. It discusses if, if/else, and while statements in Java. It includes examples of algorithms to calculate class averages using counter-controlled and sentinel-controlled repetition. It also covers topics like compound assignment operators, increment/decrement operators, and nested control structures.
Loops allow blocks of code to be repeatedly executed. The three types of loops in C are while loops, for loops, and do-while loops. While loops check the condition before each iteration. For loops allow initialization, condition checking, and increment/decrement in the loop header. Do-while loops check the condition after executing the block at least once. Break and continue statements can be used to exit or skip portions of loops. Switch statements compare a value to multiple case values and execute the corresponding block.
GCG is an elite insurance and financial services firm that has been in business for 35 years. It offers a wide range of employee benefit programs and consulting services. GCG works with over 250 producers and employees to create long-term benefit plans and has a strategic relationship with Milliman, one of the largest actuarial firms. GCG provides clients with property and casualty insurance, employee benefits, retirement plans, executive benefits, and consulting services. It also offers resources like online tools, communications support, and benchmarking surveys to help clients manage their benefits.
The episode introduces the main characters of Futurama. Philip J. Fry, a pizza delivery boy, is accidentally frozen in 1999 and awakened in 2999 in New New York City. He meets Turanga Leela, his career assignment officer, and the suicidal robot Bender. Together they track down Professor Farnsworth and are hired as the crew of his intergalactic delivery company Planet Express.
The document discusses several key object-oriented programming concepts including:
- Different types of SQL joins like inner, left, right, full outer, and left outer joins.
- The static keyword in PHP and how it allows properties and methods to be accessed without object instantiation.
- Visibility levels like public, private, and protected for class properties and methods.
- Abstract classes and interfaces, how they are similar but interfaces define contracts while abstract classes can contain partial implementations.
- The difference between exceptions which are thrown intentionally and errors which occur unintentionally.
- The difference between passing arguments by value which passes a copy versus by reference which passes a reference to the original variable.
The Planet Express Ship is the spaceship used in the animated series Futurama. It is owned and designed by Professor Farnsworth and used as the delivery ship for Planet Express. Key features of the ship include dark matter engines, laser cannons, a cyclopean windshield, and ability to travel faster than light. The ship's crew includes Captain Turanga Leela, Bender, and Fry, and it has undergone various modifications throughout the series to accomplish missions.
The document discusses several key object-oriented programming concepts including:
- Different types of SQL joins like inner, left, right, full outer, and left outer joins.
- The static keyword in PHP and how it allows properties and methods to be accessed without object instantiation.
- Visibility levels like public, private, and protected for class properties and methods.
- Abstract classes and interfaces, how they are similar but interfaces define contracts while abstract classes can have partial implementations.
- The difference between exceptions which are thrown intentionally and errors which occur unintentionally.
- The difference between pass by value which passes a copy and pass by reference which passes a reference to the original variable.
This document presents an overview of object-oriented PHP. It discusses key concepts like classes, objects, inheritance, interfaces and magic methods. It provides examples of how to define classes and objects in PHP and utilize various OOP features like visibility, abstraction, static methods and autoloading. The goal is to help PHP programmers understand object-oriented programming principles and their implementation in PHP.
The document provides definitions and explanations of various C# concepts including polymorphism, abstract methods, virtual methods, objects, classes, static methods, inheritance, virtual keyword, abstract classes, sealed modifiers, interfaces, pure virtual functions, access modifiers, reference types, overloading, overriding, encapsulation, arrays, array lists, hash tables, queues, stacks, early binding, late binding, sorted lists, and delegates. Key points covered include the differences between abstract and virtual methods, what defines a class versus an object, when to use static versus non-static methods, inheritance implementation in C#, and the purpose of interfaces.
Inheritance allows a class to inherit properties from another class. Subclasses inherit attributes and methods from the base/parent class without redefining them. Subclasses can add their own unique attributes as well. Abstract classes provide a common definition for subclasses to share but cannot be instantiated directly. Interfaces define a contract that subclasses must implement but provide no implementation. Polymorphism allows classes to take different forms through method overloading and overriding.
Interfaces allow classes to define common behaviors without specifying implementations. An interface contains abstract method signatures but no bodies. A class implements an interface by providing method implementations for all abstract methods in the interface. Interfaces establish contracts for what methods a class will have without dictating how they will behave. Common interfaces in Java include Comparable, Iterator, and Collection.
Interfaces allow classes to define common behaviors without specifying implementations. An interface contains abstract method signatures but no bodies. A class implements an interface by providing method implementations for all abstract methods in the interface. Interfaces establish contracts for what methods a class will have without defining how they will work. This allows for flexibility and multiple inheritance of behaviors.
1. The document discusses inheritance in Java, including class inheritance which allows extending classes and interface inheritance which allows implementing interfaces. It defines the keywords "extends" for class inheritance and "implements" for interface inheritance.
2. Abstract classes can contain both abstract and non-abstract methods, allowing for some default implementations, while interfaces contain only abstract methods. Interfaces define a contract that implementing classes must follow.
3. Constructors in subclasses implicitly call the parent class constructor before executing the subclass constructor body, following a top-down construction order under inheritance.
This document discusses three design patterns: Adapter, Bridge, and Composite.
The Adapter pattern allows classes with incompatible interfaces to work together by wrapping its interface into a compatible one. The Bridge pattern decouples an abstraction from its implementation, allowing them to vary independently. The Composite pattern allows treating individual objects and compositions of objects uniformly.
Polymorphism in Java allows an object to take on multiple forms. There are two types of polymorphism: compile-time polymorphism (method overloading) and runtime polymorphism (method overriding). Method overloading involves methods with the same name but different parameters, while method overriding involves subclasses providing their own implementation of a superclass method. Runtime polymorphism determines which version of a method to call based on the object's actual type at runtime. Abstraction in Java allows hiding implementation details and showing only essential functionality through the use of abstract classes and methods.
Closures allow blocks of code to access variables from the enclosing scope even after the scope has closed. This allows closures to maintain state even when passed around or returned from functions. Closures originated in Lisp and are supported in many modern languages like Python, Ruby, and C#, providing benefits like elegant iteration, filtering, and caching of results. While objects can also be used to inject strategy or share state, closures provide a more concise syntax and avoid wrapper classes in many cases.
Polymorphism in Java allows an object to take on multiple forms. There are two types of polymorphism: compile-time polymorphism (method overloading) and runtime polymorphism (method overriding). Method overloading involves methods with the same name but different parameters, while method overriding involves subclasses providing their own implementation of a superclass method. Abstract classes allow defining methods without implementation, requiring subclasses to implement them, while interfaces only define method signatures that implementing classes must then define.
Lecture 8 abstract class and interfacemanish kumar
The document discusses abstract classes and interfaces in Java. It provides examples of abstract classes with abstract and non-abstract methods, and how abstract classes can be extended. It also discusses interfaces and how they can be implemented, allow for multiple inheritance, and define marker interfaces. The key differences between abstract classes and interfaces are that abstract classes can include non-abstract methods while interfaces contain only abstract methods, and abstract classes allow single inheritance while interfaces allow multiple inheritance.
Inheritance allows classes to inherit properties and behaviors from parent classes in Java and C#. Both languages support simple, multilevel, and hierarchical inheritance through the use of extends and implements keywords. Java does not support multiple inheritance directly but allows classes to inherit from one parent class and implement multiple interfaces. Constructors and methods can be called or overridden in subclasses using the super and this keywords respectively.
OCA Java SE 8 Exam Chapter 4 Methods Encapsulationİbrahim Kürce
Methods allow classes to define reusable blocks of code. They can be declared with access modifiers like public or private, return types, parameters, and exceptions. Static methods can be called without an object and are used for utility functions. Constructors initialize new objects and can call other constructors through constructor chaining. Encapsulation involves making data private and accessing it through public getters and setters to control changes to an object's state. Immutable classes cannot be modified once created.
The document summarizes many of the new features introduced in PHP 5, including an overhauled object model with reference handling, visibility, constructors and destructors. It also discusses the Standard PHP Library (SPL) which provides classes and interfaces to solve common problems. New functions, extensions and other language improvements like type hinting and exceptions are covered. The presentation encourages developers to adopt PHP 5 features for improved object oriented programming.
The document discusses different ways to declare variables in JavaScript. There are three main keywords: var, let, and const. Var declares variables with function scope, let declares block-scoped variables, and const declares block-scoped variables that cannot be reassigned.
The document discusses application packages and classes in PeopleSoft. It defines what an application package and class are, and explains how to create them using Application Designer. It also covers object-oriented concepts like classes, objects, encapsulation, inheritance, polymorphism. Additionally, it discusses class structure, importing packages and classes, access controls, defining methods, abstract methods, interfaces, constructors, get/set methods, and exception handling.
1. Inheritance in Java allows classes to extend other classes and interfaces to implement other interfaces. This allows code reuse and establishes type constraints.
2. Abstract classes can contain both abstract and non-abstract methods while interfaces contain only abstract methods. Interfaces establish contracts that implementing classes must follow.
3. When constructing objects with inheritance, superclass constructors are called before subclass constructors. Abstract classes and interfaces allow incomplete implementations to be extended.
The document provides definitions and explanations of various object-oriented programming concepts in Delphi such as classes, objects, visibility of class members, inheritance, abstract classes, interfaces, constructors, virtual functions, polymorphism, late binding, encapsulation, properties, exceptions handling, and runtime type information (RTTI). It discusses these concepts through questions and answers. Key points covered include the relationship between classes and objects, differences between visibility levels of class members, how inheritance allows the creation of subclasses, rules around abstract classes and methods, limitations of interfaces, how to define and overload constructors and functions, use of virtual functions and polymorphism, and how RTTI is used.
This chapter discusses inheritance, polymorphism, abstract classes, interfaces, and composition in Java. It covers key concepts such as subclasses extending superclasses, overriding superclass methods, abstract classes and methods, interfaces defining common behaviors without implementations, and composition using one class as a member field of another class. The chapter objectives are to learn about these fundamental object-oriented programming concepts in Java.
1. Some of these notes are specific to PHP however the concepts typically apply to any OOP
language. For most programmers these concepts are probably already embedded in their
brains. For those of us who weren’t computer science majors or have been stuck on a project
or framework for an extended period of time this will be a good refresher as most employers
will ask questions related to these concepts in the early stages of an interview or technical
evaluation.
Different SQL JOINs
LEFT JOIN: Return all rows from the left table, even if there are no matches in the right table
RIGHT JOIN: Return all rows from the right table, even if there are no matches in the left table
INNER JOIN: produces only the set of records that match in both Table A and Table B.
SELECT * FROM TableA
INNER JOIN TableB
ON TableA.name = TableB.name
FULL OUTER JOIN: produces the set of all records in Table A and Table B, with matching
records from both sides where available. If there is no match, the missing side will contain null.
SELECT * FROM TableA
FULL OUTER JOIN TableB
ON TableA.name = TableB.name
LEFT OUTER JOIN: produces a complete set of records from Table A, with the matching
records (where available) in Table B. If there is no match, the right side will contain null.
SELECT * FROM TableA
LEFT OUTER JOIN TableB
ON TableA.name = TableB.name
To produce the set of records only in Table A, but not in Table B, we perform the same left outer
join, then exclude the records we don't want from the right side via a where clause.
SELECT * FROM TableA
LEFT OUTER JOIN TableB
ON TableA.name = TableB.name
WHERE TableB.id IS null
To produce the set of records unique to Table A and Table B, we perform the same full outer
join, then exclude the records we don't want from both sides via a where clause.
2. SELECT * FROM TableA
FULL OUTER JOIN TableB
ON TableA.name = TableB.name
WHERE TableA.id IS null
OR TableB.id IS null
Static Keyword
Declaring class properties or methods as static makes them accessible without needing an
instantiation of the class. A property declared as static can not be accessed with an instantiated
class object (though a static method can).
For compatibility with PHP 4, if no visibility declaration is used, then the property or method will
be treated as if it was declared as public.
Because static methods are callable without an instance of the object created, the pseudo-
variable $this is not available inside the method declared as static.
Static properties cannot be accessed through the object using the arrow operator ->.
Calling non-static methods statically generates an E_STRICT level warning.
Like any other PHP static variable, static properties may only be initialized using a literal or
constant; expressions are not allowed. So while you may initialize a static property to an integer
or array (for instance), you may not initialize it to another variable, to a function return value, or
to an object.
As of PHP 5.3.0, it's possible to reference the class using a variable. The variable's value can
not be a keyword (e.g. self, parent and static).
Visibility
The visibility of a property or method can be defined by prefixing the declaration with the
keywords public, protected or private. Class members declared public can be accessed
everywhere.
Protected - can be accessed only within the class itself and by inherited and parent classes.
Private - may only be accessed by the class that defines the member.
Public - can be accessed from anywhere
Property Visibility
Class properties must be defined as public, private, or protected. If declared using var without
an explicit visibility keyword, the property will be defined as public.
3. Method Visibility
Class methods may be defined as public, private, or protected. Methods declared without any
explicit visibility keyword are defined as public.
Visibility from other objects
Objects of the same type will have access to each others private and protected members even
though they are not the same instances. This is because the implementation specific details are
already known when inside those objects.
Abstract Classes & Interfaces
Abstract Classes
An abstract class is a class that is only partially implemented by the programmer. It may contain
one or more abstract methods. An abstract method is simply a function definition that serves to
tell the programmer that the method must be implemented in a child class.
Interfaces
An interface is similar to an abstract class; indeed interfaces occupy the same namespace as
classes and abstract classes. For that reason, you cannot define an interface with the same
name as a class. An interface is a fully abstract class; none of its methods are implemented and
instead of a class sub-classing from it, it is said to implement that interface. An interface defines
a contract that implementing classes must fulfill. An interface definition consists of signatures of
public members, without any implementing code.
Let’s say you had three classes - BedroomDoor, Gate and GarageDoor. Lets also imagine the
BedroomDoor and GarageDoor (and all other Doors) have a range of varying behaviour, but
both have exactly the same locking mechanisms. So we have:
PHP Code:
class Gate {
// gate specific behaviour
}
class BedroomDoor {
// bedroom door specific behaviour
public function lock($key) {
$this->lock->insert_key($key);
$key->turn('clockwise');
}
4. }
class GarageDoor {
// garage door specific behaviour
public function lock($key) {
$this->lock->insert_key($key);
$key->turn('clockwise');
}
}
Now, as you can see the two lock methods are exactly the same - duplication is evil!
All Doors can be locked in the same way (but not Gates, these are bolted shut). We can
eliminate this duplication by introducing an abstract class Door which implements this
lock method for all of the concrete instances, eliminating the duplication.
PHP Code:
abstract class Door {
public function lock($key) {
$this->lock->insert_key($key);
$key->turn('clockwise');
}
}
class BedroomDoor extends Door {
// bedroom door specific behaviour
}
class GarageDoor extends Door {
// garage door specific behaviour
}
Note that we don't necessarily have to use an abstract class to eliminate the
duplication, we could just inherit from a normal concrete Door class that can be
instantiated in its own right, depending on whether it makes sense for a Door to be
instantiated on its own.
Now, interfaces - interfaces can be used to specify a specific set of behaviour and that
behaviour's API which classes can implement. As explained above, interfaces are best
looked at as adjectives. Both doors and gates can be opened. Thats an interface right
there:
PHP Code:
interface Openable {
public function open() { }
5. }
Both doors (through the abstract Door class) and the gate can be opened, so they can
implement the interface.
PHP Code:
class Gate implements Openable {
public function open() {
if($this->is_locked()) {
$this->unlock();
}
$this->leftSide()->pullOpen();
$this->rightSide()->pullOpen();
}
}
abstract class Door implements Openable {
// our abstract class defines the open function
// as abstract as we open different types of door
// differently
abstract public function open() {}
}
class GarageDoor {
public function open() { // implement here }
}
class BedroomDoor {
public function open() { // implement here }
}
By specifying that we will implement the Openable interface, the class is bound by that
contract and you will get an error if you forget to implement any of the methods in the
interface. Finally, you can take advantage of type hinting in your methods - lets say you
need to pass an object into another class to do something - the receiving class doesn't
care what object we pass it as long as it can be opened. We can enforce this using type
hinting:
PHP Code:
class Foo {
public function openSomething(Openable $arg) {
$arg->open();
}
}
Doing the above ensures that whatever gets passed to the openSomething() method
will respond to open() because it implements the Openable interface.
6. Error vs Exception
Exceptions are thrown intentionally by code using a throw, errors... not so much.
Errors come about as a result of something which isn't handled typically. (IO errors, TCP/IP
errors, null reference errors)
Pass by value vs Pass by reference
Pass by value - A copy of the value of your variable is made, and that copy is passed to the
function you have called.
A function or subroutine that is passed a variable by value is working with a copy of that
variables’ contents. The original variables’ contents are not affected by what happens inside of
your subroutine. The scope of the copy is restricted to the lifetime of your subroutine. Upon exit,
the copy will likely be taken care of by garbage collection unless you explicitly take some sort of
action to keep it around, such as returning its value to caller.
Pass by references - A reference to location of the original variables’ contents is passed to the
function.
A function that takes a value by reference is given the address of the location in memory where
the variables’ value can be found. Any statements in the function then operate on the original
variables’ contents. Changes made will persist after your function or subroutine has run its
course.