Java string pool test doesn't work

Question

After reading about Java String Pool I've decided to run a little test. I've written the following test program that it's result doesn't match the Java String Pool behavior according to the JDK specification.

public class Temp_20141220 {

    private String b1 = "hello";

    public static void main(String[] args) {
        Temp_20141220 t = new Temp_20141220();
        String b = "hello";
        System.out.println("b==b1 =" + t.b1 == b);
    }
}

I've been expecting to get in output: b==b1 =true but I got: b==b1 =false

Why so? Does Ubuntu's JVM not support this Java String Pool feature?

Please provide code of Temp_20141220 class. – Divers Dec 28 '14 at 20:33 — Divers, Dec 28 '14 at 20:33

score 9 · Answer 1 · answered Dec 28 '14 at 20:38

9

This

System.out.println("b==b1 =" + t.b1 == b);

is equivalent to

System.out.println( ("b==b1 =" + t.b1) == b);

You're applying reference equality between b and the concatenation of "b==b1 =" and t.b1.

answered Dec 28 '14 at 20:38

Sotirios Delimanolis

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1

@JigarJoshi Thank you! It was a nice Christmas gift :) – Sotirios Delimanolis Dec 29 '14 at 13:33

score 3 · Answer 2 · answered Dec 28 '14 at 20:38

3

you're comparing 2 different strings:

string is "b==b1 =" + t.b1
string is b

if you change your code to:

System.out.println("b==b1 =" + (t.b1 == b));

you will get true in output

answered Dec 28 '14 at 20:38

Iłya Bursov

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Java string pool test doesn't work

2 Answers2