CODEWITHSUNDEEP
javacastingnullpointerexception
Andrew G
Andrew G

Reputation: 2615

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

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.

Upvotes: 11

Views: 25319

Answers (6)

Mohammed Aslam
Mohammed Aslam

Reputation: 1015

You can use Objects.equals

int foo = 1;
Integer bar = null;
Objects.equals(foo, bar);

Upvotes: 1

Bertie
Bertie

Reputation: 17697

To expand the accepted answer: i find myself having to check the equality of 2 Integer variables which might or might not be null.

So my solution would be:

boolean equals = Optional.ofNullable(objectA.getNullableInteger()).equals(Optional.ofNullable(objectB.getNullableInteger());

Upvotes: 1

nos
nos

Reputation: 229264

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;
}

Upvotes: 8

5gon12eder
5gon12eder

Reputation: 25459

I try to avoid casts whenever possible, so I'd rather use the following, which also looks nicer in my opinion:

Integer.valueOf(8).equals(m.get("null"))

Upvotes: 11

Konstantin Yovkov
Konstantin Yovkov

Reputation: 62874

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.

Upvotes: 9

biziclop
biziclop

Reputation: 49804

If only one of the arguments may be null (as is the case when you're comparing an unknown value to a constant), use equals() like this:

Integer foo = Integer.valueOf(8); // you could write Integer foo = 8; here too but I prefer to avoid autoboxing
if (foo.equals(m.get("x"))) { //will never throw an NPE because foo is never null
   ...
}

Note that your example isn't going to work in general because comparing non-primitive values with == only returns true if they refer to the same object instance. (Which in this case might even be true for very specific reasons but most of the time it isn't.)

Upvotes: 1

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