'Comparator Error java.lang.IllegalArgumentException [closed]

How can I sort array according to the count of set bits? I'm getting an error whit below code:

Arrays.sort(arr, (o1, o2) -> {
    if (Integer.bitCount(o1) <=  Integer.bitCount(o2))
        return 1;
    return -1;
});

Exception:

Exception in thread "main" java.lang.IllegalArgumentException: Comparison method violates its general contract!
    at java.base/java.util.TimSort.mergeLo(TimSort.java:781)
    at java.base/java.util.TimSort.mergeAt(TimSort.java:518)
    at java.base/java.util.TimSort.mergeCollapse(TimSort.java:448)
    at java.base/java.util.TimSort.sort(TimSort.java:245)
    at java.base/java.util.Arrays.sort(Arrays.java:1441)
    at Compute.sortBySetBitCount(File.java:44)
    at GFG.main(File.java:23)

How to fix this?

javacomparator


Solution 1:[1]

You never return 0, even if the elements are equal. Using the Comparator.comparing methods is generally better for simple sorting methods.

Arrays.sort(arr, Comparator.comparingInt(Integer::bitCount).reversed());

Sources

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Source: Stack Overflow

Solution Source
Solution 1

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