Literals In Java

Strings > Special String Operations >
Siva Nookala - 14 Apr 2016

A String literal is a sequence of characters between quotation marks, such as "string" or "literal".

Why do we need String literals?
As Strings are immutable(unchangeable) they can be shared i.e. referencing one object with many references so that we can use the memory effectively.

Storage of String literals and String objects :
String literals are stored in String-pool(Collection of Strings) and the String objects are stored in the heap memory.
Each time when you create a String literal JVM first checks whether the String is available in String-pool if the same String exists in String-pool then no new String object is created just the reference is changed. But it is not the case with String objects each time when you create Sting object using new key word each time a new object of type String is created.

Creating String literal and String objects :

String literals :

String s = "MeritCampus";

String object :

String s1 = new String("MeritCampus");

Even though both s and s1 are having same content they are not equal because s is referring to a String literal and s1 is referring to a String object.

Stringlilteral Demo

CODE

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class StringlliteralDemo
{
    public static void main(String arg[])
    {
        String literalone = "abc"; // LINE A
        String literaltwo = "abc"; // LINE B
        String obj_ref = new String("abc"); // LINE C
        //obj_ref = literaltwo; // LINE D
        if (literalone == literaltwo)
        {
            System.out.println("literalone and literaltwo are refering to same object."); // LINE E
        } 
        else
        {
            System.out.println("literalone and literaltwo are not refering to same object.");
        }
        if (literaltwo == obj_ref)
        {
            System.out.println("literaltwo and obj_ref are refering to same object."); // LINE F
        } 
        else
        {
            System.out.println("literaltwo and obj_ref are not refering to same object."); // LINE G
        }
        /*if (literaltwo.equals(s2)) // LINE H
        {
            System.out.println("literaltwo and obj_ref are having same content.");
        } 
        else
        {
            System.out.println("literaltwo and obj_ref are having different content.");
        }*/    
    }
}

OUTPUT

literalone and literaltwo are refering to same object.
literaltwo and obj_ref are not refering to same object.

DESCRIPTION

In the above program we have created two String literals one String object. Whenever we create a string literal JVM checks for the created String in the string-pool if it is not found it will add that string to String-pool that is what happened at LINE A and when we created the same string at LINE B internally no object is created just the reference is changed i.e. an extra reference literaltwo is created for already existing object in String-pool that is the reason why LINE E is executed and at LINE C we created a new String object which resides in heap memory that is reason why LINE G is executed.

THINGS TO TRY

Uncomment code at LINE D to get LINE F executed.
The output will be literaltwo and obj_ref are refering to same object. because we have assigned reference literaltwo to obj_ref at LINE D.

Uncomment code at LINE H.
The output will be literaltwo and obj_ref are having same content. Since both literaltwo and obj_ref are having same content.

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