when converting an integer value to string the string comparison fails, and returns false boolean value

Question

public class run
{
    public static void main(String args[])
    {

        boolean b;
        int i=3;
        b=Integer.toString(i)=="3";
        System.out.println(b);

    }
}

according to my code it should return true,but outputting false.

Answer 1

Youre using == when you should use:

b=Integer.toString(i).equals("3");

I don't know why you use x. I'm assuming a typo.

Basically the == compares the reference used by the literal's being compiled in to the reference to a new string object created from an integer that, due to implementation details, may or may not have been interned.

Answer 2

public class run
{
    public static void main(String args[])
    {

        boolean b;
        int i=3;
        x=Integer.toString(i).equals.("3");  // change in this line
        System.out.println(x);

    }
}

== compares the reference of object while equals method comapres the value.

Answer 3

1. You need to use equals instead of == for comparing String. Here's a good explanation as to why.

2. You should get into the habit of writing equals like this:

   x= "3".equals(Integer.toString(i));
   

   Notice how the literal value is on the left hand side and not the right hand side like all these other answers. The benefit here is this avoids a possible null pointer exception if the value passed into equals() is a null. "3" can never be null. If you wrote your code like the other answers, to be as safe as possible, you'd have to add extra lines like this:

   String s = ...
   x = s != null && s.equals("3");
   

   It's less work to write it like this:

   String s = ...
   x = "3".equals(s);