12-03-25
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			               String  Handling
			               ------------------
Q)What is a string in Java?
  =>A string is a sequence of characters represented as a single entity.
  =>A string is used to represent textual data in a Java application.
  =>A string is an object in Java.
Note:- Performing operations on string objects is nothing but string handling.

Q)How is a string created in a Java application?
=>In two ways a string is created in Java.
         1)using  new keyword
         2)using string literal

For eg.    
            String s=new String("hello");//string object created using new keyword
            String s1="hello";//string object created using a string literal
Note:- If a string is created using new keyword, the string object is stored in HEAP area of RAM.
          If a string is created using a string literal, the string object
	  is created in string constant pool.
Q)What is a string constant pool?
 =>string constant pool(string pool) is a special memory region in RAM where strings that are created using string literals  are stored by JVM.

Q)What is an immutable string?
=>non-modifiable string is known as an immutable string.
=>java.lang.String class represents immutable strings.

Q)How to compare two strings?
=>There are two methods to compare two strings(content of the strings).
           1)boolean equals()
	   2)boolean equalsIgnoreCase()

For eg.
String s1=new String("java");
String s2=new String("java");
String s3=s1.concat("Hello");
String s4=s1.concat("hello");
System.out.println(s1.equals(s2));//true	
System.out.println(s3.equals(s4));//false	
System.out.println(s3.equalsIgnoreCase(s4));//true	

Note:- to compare the content of two strings don't use equality operator(==)

Q)Important methods of java.lang.String class.
1)length():- returns the number of characters in the string.
2)equals()
3)toUpperCase()
4)toLowerCase()
5)charAt(int index)
6)trim() :- removes leading spaces and trailing spaces
7)equalsIgnoreCase()
8)substring(int index)
8)substring(int start,int end)

class Test{
	public static void main(String[] args){
	    String s1=new String("javalanguage");
	    String s2=s1.toUpperCase();
		if(s1.equals(s2)) //false
			System.out.println("strings are equal");
	        else
			System.out.println("strings are not equal");
		System.out.println(s1.charAt(2));//v
		System.out.println(s1.substring(4));//language
		System.out.println(s1.substring(4,11));//4th index to 10th indext chars printed
                String s5="    hello      "	;
		System.out.println("hi"+s5+"nice");//hi     hello      nice
		String s6=s5.trim();//hello
		System.out.println("hi"+s6+"nice");//hihellonice

	}
}