Why these strings are not holding the same reference of the object.

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As we all know, Java will not create a new string constant if it already exists in the String Constants Pool. But by that logic, shouldn't s1==s5 and others be true? None of the strings I created used the "new" keyword.

What I have tried:

Java

public class strings1 {

    public static void main(String[] args) {

        // String str = new String("very");

        String s1 = "mynameisbond";
        String s2 = "myname" + "isbond";
        String s3 = "myname";
        String s4 = "isbond";
        String s5 = s3 + s4;
        String s6 = "myname" + s4;
        String s7 = s3.concat(s4);

        System.out.println(s1 == s2); // true
        System.out.println(s1 == s5); // false
        System.out.println(s5 == s6); // false
        System.out.println(s2 == s7); // false

    }

}

Posted 2-Aug-23 2:52am

Sharyar Javaid

Updated 11-Aug-23 11:05am

Deeksha Shenoy

v2

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OriginalGriff · Accepted Answer · 2023-08-02T03:29:00

No, because

String s1 = "mynameisbond";

uses a single string literal and

String s2 = "myname" + "isbond";

uses two that can be combined at compile time into a single literal.
But s5, s6, and s7 all get assigned at run time, not compile - so the strings they contain are not string literals: they are not "known" at compile time so they do not get added to the Constants Pool.

Quote:
If i do: String greet = new String("hello") , I know the string "hello" will be allocated to the HEAP but at the same time this "hello" will also be created in String Constant Pool? so in the next line if I do: String greet2 = "hello" , greet2 will point to the already existing "hello" by greet in the String Constant Pool or it never existed there because of new keyword of greet?

There are two ways to create a string:

Java

String s="Welcome";

This creates a variable called s which "points" to a literal string "Welcome" in the Constant Pool.

Java

String s=new String("Welcome");

This creates a variable called s, a string literal "Welcome" in the Constant Pool unless it already exists there, and a copy of the literal the heap - s "points" at the heap version.
The new keyword always constructs a heap based variable.