Java: Converting Integer to String. Comparing with == equals operator

Question

public static void main(String[] args) {
    Integer i = new Integer(4);
    System.out.println(i.toString());
    if (i.toString() == i.toString()) {
        System.out.println("true how");
    } else {
        System.out.println("false how");
    }

}

While executing above code, I am getting output as "false how".

Can you explain how Jvm treats this object?

Because the `==` operator tests for *object identity* not *equality*. `Integer.toString` need not return identical objects on multiple invocations. — 5gon12eder, Dec 23 '14 at 07:16
[How do I compare strings in Java?](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java) — Michaël, Dec 23 '14 at 07:17
@5gon12eder thanks .. so Integer.toString creates new object every time. while exectuing if (i.toString() == i.toString()) this line, totally two objects created. My understanding is right? thanks in advance. — Prabhu, Dec 23 '14 at 07:26
It may or may not create new objects. As you've tested above code, it seems to have created two different objects. You just cannot rely on it. — 5gon12eder, Dec 23 '14 at 07:33

score 2 · Answer 1 · answered Dec 23 '14 at 07:16

2

You must compare objects with equals() method.

i.toString().equals(i.toString())

answered Dec 23 '14 at 07:16

Tkachuk_Evgen

1,334
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17

Syed Mauze Rehan · Accepted Answer · 2014-12-31T15:50:21.637

2

toString() creates a new string object every time and your code is actually checking if both references are the same, which is never the case so it runs the else case. If you try

i.toString().equals(i.toString())

you'll get the desired output.

edited Dec 31 '14 at 15:50

answered Dec 23 '14 at 07:16

Syed Mauze Rehan

1,125
14
31

Java: Converting Integer to String. Comparing with == equals operator

2 Answers2