What is the cleanest way to compare an int with a potentially null Integer in Java?

Question

Map<String,Integer> m;
m = new TreeMap<String,Integer>();

Is it good practice to add the following cast just to avoid the null pointer exception when m.get() is null.

System.out.println( ((Integer) 8).equals( m.get("null") ) ); // returns false

Alternatively with a prior null check it starts to look a bit ugly.

System.out.println( m.contains("null") != null && m.get("null").equals( 8 ) );

Is there a better way to write this? Thanks.

Answer 1

The == operator doesn't compare values, but references.

You should use the .equals() method, instead, applied to the Integer variable (for which you are sure that is not null and NPE won't be thrown):

Integer eight = 8; //autoboxed
System.out.println(eight.equals(m.get("null")));

This will print false even the m.get("null") returns null.

Answer 2

No, because it will not work. You can't compare two Integer with ==, as that compares references and not the integer values. See more info in this question

You'll need a helper method, such as:

boolean safeIntegerCompare(Integer a, int b)
{
    if (a != null) 
      return a.intValue() == b;
    return false;
}