Question

The following statement appears in Section 3.10.5. String Literals of the Java Language Specification:

A string literal always refers to the same instance of class String.
This is because string literals – or, more generally, strings that are
the values of constant expressions (§15.28) – are “interned” so as to
share unique instances, using the method String.intern.

I am using Java JDK 7 and Eclipse indigo.

and my test program is as follows:

public class Main {

    public static void main(String[] args) {
        String s1 = "string";
        String s2 = "string";

        System.out.print(s1 == s2); // true
        System.out.print(" , " + "string" == "string"); // false
    }

}

Answer 1

This is an operator precedence issue. The == operator has a lower precedence than the + operator.

What you are actually testing is whether (" , " + "string") is equal to "string". It isn’t.

If you mean that to compare "string" and "string" you should write:

    System.out.print(" , " + ("string" == "string"));

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The standard advice of not using == to test strings applies too … but that’s not what is giving you the confusing output.