JAVA STRINGS

Java String provides a lot of concepts that can be performed on a string such as compare, concat, equals, split, length, replace, compareTo, intern, substring etc.

In java, string is basically an object that represents sequence of char values.

An array of characters works same as java string. For example:

char[] ch={'j','a','v','a'};

String s= new String(ch);

is same as 

String s="java";

WHAT IS STRING IN JAVA?

Generally, string is a sequence of characters. But in java, string is an object that represents a sequence of characters. String class is used to create string object.

HOW TO CREATE STRING OBJECT ?

There are two ways to create String object:

1. By string literal
2. By new keyword

1.String Literal

Java String literal is created by using double quotes. For Example:

String s="java";

Each time you create a string literal, the JVM checks the string constant pool first. If the string already exists in the pool, a reference to the pooled instance is returned. If string doesn't exist in the pool, a new string instance is created and placed in the pool. For example:

String s1="java";

String s2="java";//will not create new instance

WHY JAVA USES CONCEPT OF STRING LITERAL?

To make Java more memory efficient (because no new objects are created if it exists already in string constant pool).

2.New Keyword

String s=new String("Java");//creates two objects and one reference variable  

In such case, JVM will create a new string object in normal(non pool) heap memory and the literal "Java" will be placed in the string constant pool. The variable s will refer to the object in heap(non pool).