Int2IntHashMap methods don't work when using map via interface

[vladimir-lifar]

Some methods of Int2IntHashMap don't actually override corresponding methods of java.util.Map. Due to this fact we can't expose Int2IntHashMap as a Map<Integer, Integer> to external code.

computeIfAbsentUsingImplementation() works well, but computeIfAbsentUsingInterface() fails, because it uses java.util.Map.computeIfAbsent(...) which is not overridden.

@Test
public void computeIfAbsentUsingImplementation() {
    Int2IntHashMap int2IntHashMap = new Int2IntHashMap(-1);
    int key = 0;
    int result = int2IntHashMap.computeIfAbsent(key, k -> k);
    Assert.assertEquals(key, result);
}

@Test
public void computeIfAbsentUsingInterface() {
    Map<Integer, Integer> map = new Int2IntHashMap(-1);
    int key = 0;
    int result = map.computeIfAbsent(key, k -> k);
    Assert.assertEquals(key, result);
}

Agrona 0.9.3, JDK 8

[RichardWarburton]

You shouldn't need to override computeIfAbsent, should be fine to inherit the default if you implement the Map interface properly. Looks like we're not dealing with nulls properly on get() or put(). I'll take a look.

[RichardWarburton]

Thanks for the bug report.

[vladimir-lifar]

@RichardWarburton, @mjpt777 many thanks for the fix!