如果方法参数是原始int，那么方法内循环中的myArrayList.contains（primitiveArg）效率极低还是可以？

Question

I have code like this:

public int getDistanceToNumber(int number) {
    List<Integer> tuple5 = null;
    int distanceCounter = 0;
    for (int i = 0; i < allDraws.size(); i++) {
        tuple5 = allDraws.get(i).getTupleAsList();
        if (tuple5.contains(number)) {  // autoboxing primitive ?

        }

    }

    return 0;
}

The question is - shall I make method argument Integer like int getDistanceToNumber(Integer number) for autoboxing from primitive into Integer to happen only once, or there is no performance issue.

This piece of code inside loop runs over 100K times...

Answer 1

You should test that under a JMH .

• You can avoid the boxing problem by using a Integer.valueOf(int) once and passing it to List::contains(Object) .
• The compiler may be efficient enough to understand that number is never changed and do that for you.

For the rest, without more information (type of allDraws ?), there might be other optimization to do before boxing conversion.