String is the most commonly used pre-defined class in Java. String is part of java.lang package.

String class is Immutable. Once String is created, it can not be modified or changed.
String implements Serializable, Comparable and CharSequence interfaces.

public final class String
    implements, Comparable, CharSequence {


String Concepts

(1.)toString()in String
(2.)Substring in Java
(3.)StringTokenizer in Java
(4.)Difference between String concatenation operator (+) and concat() Method
(5.)Difference Between hasMoreElements() and hasMoreTokens() in StringTokenizer

String Methods

(1.)Convert String to Integer – parseInt()
(2.)String replace() Method
(3.)String replaceAll() Method
(4.)String charAt() Method
(5.)String equals() Method
(6.)String length() Method
(7.)String contains() Method
(8.) String equalsIgnoreCase() Method

(9.) String isEmpty() Method
(10.)String toLowerCase() Method
(11.)String toUpperCase() Method
(12.)String trim() Method
(13.)String startsWith() Method

(14.)String concat() Method
(15.)String toCharArray() Method
(16.)String endsWith() Method

(17.)String compareTo() Method

Problems Based on String

(1.)How to Convert char to String in Java
(2.)Problems on String – Set 1
(3.)Problem on String – Set II
(4.) Convert char array to String
(5.) Program to Print Permutations of a String