String handling in Java

Creating String Object

There are two ways to create String object:

By string literal	By new keyword
String literal is created by double quote. String s = "Hello";	String literal is created by using new key word. String s = new String("Welcome");
Each time you create a string literal, the JVM first checks the string constant pool. If the string already exists in the pool, a reference to the pooled instance returns. If the string does not exist in the pool, a new String object instantiates then is placed in the pool.	JVM will create a new String object in normal Heap memory. The variable will refer to the object in Heap.
Applicable only for String class. (Not applicable for StringBuilder, StringBuffer classes.)	Applicable for String , StringBuilder, StringBuffer classes.

Consider below code with four different string variables s1, s2, s3, s4 assigned with string values. Let us see what happens inside.

package com.java4coding;

public class StringHandling {

public static void main(String[] args) {

String s1 = "Adi";

String s2 = "Adi

String s3 = new String("Adi");

StringBuilder s4 = new StringBuilder("Adi");

}

String s1 = "Adi";	New String Constant created in string constant pool, s1 is returned to this.
String s2 = "Adi	No new object is created, s2 is returned with the same above string present in string constant pool.
String s3 = new String("Adi");	JVM will create a new String object in Heap memory and the literal "Adi" will be placed in the string constant pool. The variable s3 will refer to the object in Heap.
StringBuilder s4 = new StringBuilder("Adi");	JVM will create a new String object in Heap memory and the literal "Adi" will be placed in the string constant pool. The variable s4 will refer to the object in Heap.

String class is immutable. StringBuffer and StringBuilder classes are mutable (modifiable) strings.

Let's try to understand the immutability concept by the example given below:

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