Comparison Method Violates Its General Contract! (Part 2)
summary
Explains why a buggy Comparator triggers "comparison method violates its general contract": TimSort used by Java 7+ detects inconsistent ordering, so incorrect logic can throw an exception or silently produce wrong order. Shows Java 8 combinators used to build correct comparators (comparingInt/comparingDouble, thenComparing, nullsFirst/nullsLast), demonstrates BigDecimal’s compareTo inconsistent with equals causing TreeSet vs HashSet surprises, and warns against setting java.util.Arrays.useLegacyMergeSort because it hides bugs rather than fixing them.
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chapters (10)
- 0:00Start
- 0:18Combinator Methods on the Comparator Interface
- 1:16Combinator Methods
- 2:44Demo
- 6:39Comparing Int
- 8:26Nullpointerexception
- 16:27The Illegal Argument Exception
- 16:42Java Util Arrays Use Legacy Merge Sort
- 19:09A Downstream Comparator
- 24:12Numeric Consistency Properties
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