Java Lang package,Math class.......

1. JAVA UNIT 2(Part 1)
BY: SURBHI SAROHA

2. SYLLABUS
 Java Lang package
 Simple type wrappers
 Number,Double,float,byte,short,int,long,character,Boolean,process and void.
 The Maths class.
 Java Utility and Collection Classes.

3. Cont….
 Arrays as collections
 Algorithms
 Wrappers as implementations
 Extending the abstract implementation legacy collections
 Framework classes
 Traversing collections with enumeration’s

4. Java Lang package
 Provides classes that are fundamental to the design of the Java programming language.
 The most important classes are Object, which is the root of the class hierarchy, and Class, instances
of which represent classes at run time.
 Following are the Important Classes in Java.lang package :
 Boolean: The Boolean class wraps a value of the primitive type boolean in an object.
 Byte: The Byte class wraps a value of primitive type byte in an object.
 Character – Set 1, Set 2: The Character class wraps a value of the primitive type char in an object.
 Character.Subset: Instances of this class represent particular subsets of the Unicode character set.
 Character.UnicodeBlock: A family of character subsets representing the character blocks in the
Unicode specification.
 Class – Set 1, Set 2 : Instances of the class Class represent classes and interfaces in a running Java
application.

5. Cont…
 ClassLoader: A class loader is an object that is responsible for loading classes.
 ClassValue: Lazily associate a computed value with (potentially) every type.
 Compiler: The Compiler class is provided to support Java-to-native-code compilers and related
services.
 Double: The Double class wraps a value of the primitive type double in an object.
 Enum: This is the common base class of all Java language enumeration types.
 Float: The Float class wraps a value of primitive type float in an object.
 InheritableThreadLocal: This class extends ThreadLocal to provide inheritance of values from
parent thread to child thread: when a child thread is created, the child receives initial values for all
inheritable thread-local variables for which the parent has values.
 Integer :The Integer class wraps a value of the primitive type int in an object.
 Long: The Long class wraps a value of the primitive type long in an object.

6. Cont…
 Math – Set 1, Set 2: The class Math contains methods for performing basic
numeric operations such as the elementary exponential, logarithm, square root,
and trigonometric functions.
 Number: The abstract class Number is the superclass of classes BigDecimal,
BigInteger, Byte, Double, Float, Integer, Long, and Short.
 Object: Class Object is the root of the class hierarchy.
 Package: Package objects contain version information about the implementation
and specification of a Java package.
 Process: The ProcessBuilder.start() and Runtime.exec methods create a native
process and return an instance of a subclass of Process that can be used to control
the process and obtain information about it.
 ProcessBuilder: This class is used to create operating system processes.

7. Cont…
 Math – Set 1, Set 2: The class Math contains methods for performing basic
numeric operations such as the elementary exponential, logarithm, square root,
and trigonometric functions.
 Number: The abstract class Number is the superclass of classes BigDecimal,
BigInteger, Byte, Double, Float, Integer, Long, and Short.
 Object: Class Object is the root of the class hierarchy.
 Package: Package objects contain version information about the implementation
and specification of a Java package.
 Process: The ProcessBuilder.start() and Runtime.exec methods create a native
process and return an instance of a subclass of Process that can be used to control
the process and obtain information about it.
 ProcessBuilder: This class is used to create operating system processes.

8. Cont…
 StringBuffer: A thread-safe, mutable sequence of characters.
 StringBuilder: A mutable sequence of characters.
 System: The System class contains several useful class fields and methods.
 Thread: A thread is a thread of execution in a program.
 ThreadGroup: A thread group represents a set of threads.
 ThreadLocal: This class provides thread-local variables.
 Throwable: The Throwable class is the superclass of all errors and exceptions in the
Java language.
 Void: The Void class is an uninstantiable placeholder class to hold a reference to
the Class object representing the Java keyword void.

9. Simple type wrappers
 A Wrapper class is a class whose object wraps or contains primitive data types.
 When we create an object to a wrapper class, it contains a field and in this field, we
can store primitive data types.
 In other words, we can wrap a primitive value into a wrapper class object.
 Need of Wrapper Classes
 They convert primitive data types into objects. Objects are needed if we wish to
modify the arguments passed into a method (because primitive types are passed
by value).
 The classes in java.util package handles only objects and hence wrapper classes
help in this case also.

10. Cont….
 Data structures in the Collection framework, such as ArrayList and Vector, store
only objects (reference types) and not primitive types.
 An object is needed to support synchronization in multithreading.
 Primitive Data types and their Corresponding Wrapper class

11. Number,Double,float,byte,short,int,
long,character,Boolean,process and void.
 int myNum = 5; // Integer (whole number)
 float myFloatNum = 5.99f; // Floating point number
 char myLetter = 'D'; // Character
 boolean myBool = true; // Boolean
 String myText = "Hello"; // String
 Data types are divided into two groups:
 Primitive data types - includes byte, short, int, long, float, double, boolean and char
 Non-primitive data types - such as String, Arrays and Classes

12. There are eight primitive data types in Java:
 Data Type Size Description
 byte 1 byte Stores whole numbers from -128 to 127
 short 2 bytes Stores whole numbers from -32,768 to 32,767
 int 4 bytes Stores whole numbers from -2,147,483,648 to 2,147,483,647
 long 8 bytes Stores whole numbers from -9,223,372,036,854,775,808 to
9,223,372,036,854,775,807
 float 4 bytes Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits
 double 8 bytes Stores fractional numbers. Sufficient for storing 15 decimal digits
 boolean 1 bit Stores true or false values
 char 2 bytes Stores a single character/letter or ASCII values

13. The Maths class
 Java Math class provides several methods to work on math calculations like min(), max(), avg(), sin(),
cos(), tan(), round(), ceil(), floor(), abs() etc.
 Example 1
 public class JavaMathExample1
 {
 public static void main(String[] args)
 {
 double x = 28;
 double y = 4;

 // return the maximum of two numbers
 System.out.println("Maximum number of x and y is: " +Math.max(x, y));

14. Cont…
 // return the square root of y
 System.out.println("Square root of y is: " + Math.sqrt(y));

 //returns 28 power of 4 i.e. 28*28*28*28
 System.out.println("Power of x and y is: " + Math.pow(x, y));

 // return the logarithm of given value
 System.out.println("Logarithm of x is: " + Math.log(x));
 System.out.println("Logarithm of y is: " + Math.log(y));

 // return the logarithm of given value when base is 10
 System.out.println("log10 of x is: " + Math.log10(x));
 System.out.println("log10 of y is: " + Math.log10(y));

15. Cont….
 // return the log of x + 1
 System.out.println("log1p of x is: " +Math.log1p(x));

 // return a power of 2
 System.out.println("exp of a is: " +Math.exp(x));

 // return (a power of 2)-1
 System.out.println("expm1 of a is: " +Math.expm1(x));
 }
 }

16. Java Utility and Collection Classes.
 Collections class in java is a useful utility class to work with collections in java.
 The java.util.Collections class directly extends the Object class and exclusively
consists of the static methods that operate on Collections or return them.
 Collections Class in java
 Collections class contains polymorphic algorithms that operate on collections and
“wrappers” — which return a new collection backed by a specified collection. It is a
member of Java Collections Framework.
 Collections class fields
 Collections class contains 3 fields: EMPTY_LIST, EMPTY_SET, EMPTY_MAP, which can
be used to get immutable empty List, Map and Set respectively.

17. Example
 package utility;
 import java.util.Collections;
 import java.util.ArrayList;
 import java.util.List;
 public class CollectionsDemo {
 public static void main(String[] args) {
 List<String>student<String>List = new ArrayList();
 studentList.add("Neeraj");
 studentList.add("Mahesh");
 studentList.add("Armaan");


18. Cont….
 studentList.add("Preeti");
 studentList.add("Sanjay");
 studentList.add("Neeraj");
 studentList.add("Zahir");
 System.out.println("Original List " + studentList);
 Collections.sort(studentList);
 System.out.println("Sorted alphabetically List " + studentList);
 Collections.reverse(studentList);
 }

19. Cont….
 System.out.println("Reverse List " + studentList);
 Collections.shuffle(studentList);
 System.out.println("Shuffled List " + studentList);
 System.out.println("Checking occurance of Neeraj: "
 + Collections.frequency(studentList, "Neeraj"));

20. THANK YOU 