Introduction of String

Introduction of String

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={’l',’e',’a',’r',’w',’i',’t',’h',’r',’e’,’s’,’h’,’u’};

String s=new String(ch);

is same as:

String s=”learnwithreshu";

The java.lang.String class implements Serializable, Comparable and CharSequence interfaces.

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. The java.lang.String class is used to create a string object. then Question arises that 

How to create a string object? 

There are two ways to create String object:

By string literal

By new keyword

String Literal

Java String literal is created by using double quotes. 

For Example:

String s=”Reshu";

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 the string doesn't exist in the pool, a new string instance is created and placed in the pool. For example:

String s1=“Welcome";  

      String s2=“Welcome";

      s2 doesn't create a new instance 

 String objects are stored in a special 

 memory area known as the 

     "string constant pool".

By new keyword

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

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

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