Learn Java in 2 days
By Ahmed Ali Ali © 2013
Email : ahmed14ghaly@gmail.com
a14a2a1992a@yahoo.com

By Ahmed Ali Ali © 2013...
Agenda
First day

Second day (soon)

•Introduction
•Class

•File

Declarations & Modifiers

•Wrapper

Classes

•Handling

...
Introduction
•

Java is an object-oriented programming language .

•

Java was started as a project called "Oak" by James ...
Complete List of Java Keywords

By Ahmed Ali Ali © 2013

4
My First Java Program

By Ahmed Ali Ali © 2013

5
Class Declarations
•

Source File Declaration Rules

o only one public class per source code file.
o A file can have more ...
Class Access(Class Modifiers)
• What

•

does it mean to access a class?

Class Modifiers
o Public Access
o Default Access...
Declare Interfaces
• An

interface must be declared with the keyword interface.

• All

interface methods are implicitly p...
Declare Class Members
•We've

looked at what it means to use a modifier in a class declaration, and now
we'll look at what...
Determining Access to Class
Member

By Ahmed Ali Ali © 2013

10
Develop Constructors
• The

•

constructor name must match the name of the class.

If you don't type a constructor into yo...
Variable Declarations
•

There are two types of variables in Java:

o Primitives : A primitive can be one of eight types: ...
Variable Scope

By Ahmed Ali Ali © 2013

13
if and switch Statements
• The

•

only legal expression in an if statement is a boolean expression.

Curly braces are opt...
Ternary (Conditional Operator)
Returns one of two values based on whether a boolean expression is true or
false.
•

•

Ret...
String Concatenation Operator
•

If either operand is a String, the + operator concatenates the operands.

•

If both oper...
Overloading & Overriding
• Abstract

methods must be overridden by the first concrete (subclass).

•

final methods cannot...
Overloading & Overriding (cont’)
•

Methods from a superclass can be overloaded in a subclass.

•

constructors can be ove...
Stack and Heap—Quick Review
•

understanding the basics of the stack and the heap makes it far easier to
understand topics...
Wrapper Classes
•What’s consept of Wrapper Class ?
•The wrapper classes correlate to the primitive types
•The three most i...
Handling Exceptions
• The

term "exception" means "exceptional condition" and is an occurrence that

alters the normal pro...
Handling Exceptions (cont’)

Example :

By Ahmed Ali Ali © 2013

22
Assertion Mechanism
•

the assertion mechanism, added to the language with version 1.4, gives you
a way to do testing and ...
Assertion Mechanism
Use assertions for internal logic checks within your code, and normal exceptions for
error conditions ...
immutable
•

an immutable object is an object whose state cannot be modified after it is

created
•Strings

Are Immutable ...
StringBuffer, and StringBuilder
•

The java.lang.StringBuffer and java.lang.StringBuilder classes should

be used when you...
Dates, Numbers, and Currency
•

Here are the date related classes you'll need to understand.

o java.util.Date
o java.util...
Dates, Numbers, and Currency
(cont’)

By Ahmed Ali Ali © 2013

28
Dates, Numbers, and Currency
(cont’)

By Ahmed Ali Ali © 2013

29
A Search Tutorial
• To

find specific pieces of data in large data sources, Java provides several
mechanisms that use the ...
A Search Tutorial (cont’)
[abc] Searches only for a's, b's or c's

[a-f] Searches only for a, b, c, d, e, or f characters
...
Tokenizing
• Tokenizing

is the process of taking big pieces of source data, breaking

them into little pieces, and storin...
Tokenizing (cont’)
Tokenizing with String.split()

By Ahmed Ali Ali © 2013

33
Quiz

By Ahmed Ali Ali © 2013

34
Questions
By Ahmed Ali Ali © 2013

35
Thanks
By Ahmed Ali Ali © 2013

36
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Learn Java in 2 days

  1. 1. Learn Java in 2 days By Ahmed Ali Ali © 2013 Email : ahmed14ghaly@gmail.com a14a2a1992a@yahoo.com By Ahmed Ali Ali © 2013 1
  2. 2. Agenda First day Second day (soon) •Introduction •Class •File Declarations & Modifiers •Wrapper Classes •Handling I/O •inner class Exceptions •Threads •Collections •immutable •StringBuffer, and •Tokenizing •Quiz StringBuilder •Utility Classes: Collections and Arrays •Generics •Quiz By Ahmed Ali Ali © 2013 2
  3. 3. Introduction • Java is an object-oriented programming language . • Java was started as a project called "Oak" by James Gosling in June1991. Gosling's goals were to implement a virtual machine and a language that had a familiar Clike notation but with greater uniformity and simplicity than C/C++. The first public implementation was Java 1.0 in 1995 • The language itself borrows much syntax from C and C++ but has a simpler object model and fewer low-level facilities. • Java Is Easy to Learn By Ahmed Ali Ali © 2013 3
  4. 4. Complete List of Java Keywords By Ahmed Ali Ali © 2013 4
  5. 5. My First Java Program By Ahmed Ali Ali © 2013 5
  6. 6. Class Declarations • Source File Declaration Rules o only one public class per source code file. o A file can have more than one nonpublic class. o If there is a public class in a file, the name of the file must match the name of the public class. o If the class is part of a package, the package statement must be the first line in the source code file, before any import statements that may be present o import and package statements apply to all classes within a source code file. By Ahmed Ali Ali © 2013 6
  7. 7. Class Access(Class Modifiers) • What • does it mean to access a class? Class Modifiers o Public Access o Default Access • package cert; Public class Beverage { } package cert; class Beverage { } Other (Non access) Class Modifiers o Final Classes package cert; Final class Beverage { } o Abstract Classes package cert; Abstract class Beverage { } By Ahmed Ali Ali © 2013 7
  8. 8. Declare Interfaces • An interface must be declared with the keyword interface. • All interface methods are implicitly public and abstract. In other words, you do not need to actually type the public or abstract . • Interface methods must not be static. • Because interface methods are abstract, they cannot be marked final, • All variables defined in an interface must be public, static, and final. • An interface can extend one or more other interfaces. • An interface cannot implement another interface or class. By Ahmed Ali Ali © 2013 8
  9. 9. Declare Class Members •We've looked at what it means to use a modifier in a class declaration, and now we'll look at what it means to modify a method or variable declaration. • Access o o o o • Modifiers public protected default private Nonaccess Member Modifiers o Final and abstract o Synchronized methods By Ahmed Ali Ali © 2013 9
  10. 10. Determining Access to Class Member By Ahmed Ali Ali © 2013 10
  11. 11. Develop Constructors • The • constructor name must match the name of the class. If you don't type a constructor into your class code, a default constructor will be automatically generated by the compiler. • Constructors must not have a return type. • Constructors can use any access modifier, • Every class, including abstract classes, MUST have a constructor. • constructors are invoked at runtime when you say new on some class. By Ahmed Ali Ali © 2013 11
  12. 12. Variable Declarations • There are two types of variables in Java: o Primitives : A primitive can be one of eight types: char, boolean, byte, short, int, long, double, or float. Once a primitive has been declared, its primitive type can never change, although in most cases its value can change. o Reference variables : A reference variable is used to refer to (or access) an object. A reference variable is declared to be of a specific type and that type can never be changed. • Note : o It is legal to declare a local variable with the same name as an instance variable; this is called "shadowing." By Ahmed Ali Ali © 2013 12
  13. 13. Variable Scope By Ahmed Ali Ali © 2013 13
  14. 14. if and switch Statements • The • only legal expression in an if statement is a boolean expression. Curly braces are optional for if blocks that have only one conditional statement. • switch statements can evaluate only to enums or the byte, short, int, and char data types.You can't say, By Ahmed Ali Ali © 2013 14
  15. 15. Ternary (Conditional Operator) Returns one of two values based on whether a boolean expression is true or false. • • Returns the value after the ? if the expression is true. • Returns the value after the : if the expression is false. x = (boolean expression) ? value to assign if true : value to assign if false By Ahmed Ali Ali © 2013 15
  16. 16. String Concatenation Operator • If either operand is a String, the + operator concatenates the operands. • If both operands are numeric, the + operator adds the operands. By Ahmed Ali Ali © 2013 16
  17. 17. Overloading & Overriding • Abstract methods must be overridden by the first concrete (subclass). • final methods cannot be overridden. • Only inherited methods may be overridden, and remember that private methods are not inherited. •A subclass uses super. overriddenMethodName() to call the superclass version of an overridden method. • Object type (not the reference variable's type), determines which overridden method is used at runtime. By Ahmed Ali Ali © 2013 17
  18. 18. Overloading & Overriding (cont’) • Methods from a superclass can be overloaded in a subclass. • constructors can be overloaded but not overridden. • Overloading means reusing a method name, but with different arguments. • Overloaded methods. o Must have different argument lists o May have different return types, if argument lists are also different o May have different access modifiers o May throw different exceptions • Polymorphism applies to overriding, not to overloading. • Reference type determines which overloaded method will be used at compile time. By Ahmed Ali Ali © 2013 18
  19. 19. Stack and Heap—Quick Review • understanding the basics of the stack and the heap makes it far easier to understand topics like argument passing, threads, exceptions, • Instance variables and objects live on the heap. • Local variables live on the stack. By Ahmed Ali Ali © 2013 19
  20. 20. Wrapper Classes •What’s consept of Wrapper Class ? •The wrapper classes correlate to the primitive types •The three most important method families are o xxxValue() Takes no arguments, returns a primitive o parseXxx() Takes a String, returns a primitive o valueOf() Takes a String, returns a wrapped object By Ahmed Ali Ali © 2013 20
  21. 21. Handling Exceptions • The term "exception" means "exceptional condition" and is an occurrence that alters the normal program flow. • Exception handling allows developers to detect errors easily without writing special code to test return values. •A bunch of things can lead to exceptions, including hardware failures, resource exhaustion, and good old bugs. When an exceptional event occurs in Java, an exception is said to be "thrown." The code that's responsible for doing something about the exception is called an "exception handler," and it "catches" the thrown exception. By Ahmed Ali Ali © 2013 21
  22. 22. Handling Exceptions (cont’) Example : By Ahmed Ali Ali © 2013 22
  23. 23. Assertion Mechanism • the assertion mechanism, added to the language with version 1.4, gives you a way to do testing and debugging checks on conditions you expect to smoke out while developing, • writing code with assert statement will help you to be better programmer and improve quality of code, yes this is true based on my experience when we write code using assert statement we think through hard, we think about possible input to a function, we think about boundary condition which eventually result in better discipline and quality code. "If" is a conditional operator with a specific loop syntax. It can be followed with the loop continuation syntax "else". The "Assert" keyword will throw a run-time error if the condition of the loop returns 'false' and is used for conditional validation(parameter checking). Assertions are mainly used to debug code and are generally removed in a live product. Both "If" & "Assert" evaluate a Boolean condition. • By Ahmed Ali Ali © 2013 23
  24. 24. Assertion Mechanism Use assertions for internal logic checks within your code, and normal exceptions for error conditions outside your immediate code's control. Really simple: private void doStuff() { assert (y > x); // more code assuming y //is greater than x } Simple: private void doStuff() { assert (y > x): "y is " + y + " x is " + x; // more code assuming y is greater than x } By Ahmed Ali Ali © 2013 24
  25. 25. immutable • an immutable object is an object whose state cannot be modified after it is created •Strings Are Immutable Objects By Ahmed Ali Ali © 2013 25
  26. 26. StringBuffer, and StringBuilder • The java.lang.StringBuffer and java.lang.StringBuilder classes should be used when you have to make a lot of modifications to strings of characters • StringBuilder is not thread safe. In other words, its methods are not synchronized. • StringBuilder runs faster. By Ahmed Ali Ali © 2013 26
  27. 27. Dates, Numbers, and Currency • Here are the date related classes you'll need to understand. o java.util.Date o java.util.Calendar o java.text.DateFormat o java.text.NumberFormat o java.util.Locale By Ahmed Ali Ali © 2013 27
  28. 28. Dates, Numbers, and Currency (cont’) By Ahmed Ali Ali © 2013 28
  29. 29. Dates, Numbers, and Currency (cont’) By Ahmed Ali Ali © 2013 29
  30. 30. A Search Tutorial • To find specific pieces of data in large data sources, Java provides several mechanisms that use the concepts of regular expressions (Regex). Simple Searches we'd like to search through the following source String (abaaaba) for all occurrences (or matches) of the expression (ab) . • What the result if we search on (aba) inside the String (abababa) ? By Ahmed Ali Ali © 2013 30
  31. 31. A Search Tutorial (cont’) [abc] Searches only for a's, b's or c's [a-f] Searches only for a, b, c, d, e, or f characters d A digit s A whitespace character w A word character (letters, digits, or "_" (underscore)) the quantifier that represents "one or more" is the "+" (Ex. d+) Example : source: "a 1 56 _Z" index: 012345678 pattern: w In this case will return positions 0, 2, 4, 5, 7, and 8. By Ahmed Ali Ali © 2013 31
  32. 32. Tokenizing • Tokenizing is the process of taking big pieces of source data, breaking them into little pieces, and storing the little pieces in variables. Tokens and Delimiters source: "ab,cd5b,6x,z4" If we say that our delimiter is a comma, then our four tokens would be ab cd5b 6x z4 By Ahmed Ali Ali © 2013 32
  33. 33. Tokenizing (cont’) Tokenizing with String.split() By Ahmed Ali Ali © 2013 33
  34. 34. Quiz By Ahmed Ali Ali © 2013 34
  35. 35. Questions By Ahmed Ali Ali © 2013 35
  36. 36. Thanks By Ahmed Ali Ali © 2013 36

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