RecapDifficulty: Advanced1 min

Recap: Sorting Your Own Types

The comparison question, who owns the order, chains, overflow, and consistency.

Sorting your own types comes down to the five ideas below, each listed with the card that covers it.

What the topic established, and which card it was on
The idea	Where
Every sort rests on one two-argument question: which comes first	Sorting Your Own Types: The Comparison Every Sort Relies On
`Comparable` puts the order on the type; `Comparator` puts it at the call	Comparable vs Comparator
`thenComparing` acts on ties; `reversed()` reverses everything to its left	Building a Comparator on Two Fields With One Reversed
Subtracting two `int` values can overflow and flip the sign	Integer Overflow in Comparators: Why Subtraction Is a Bug
An inconsistent comparator throws on some lists and misorders others	Comparator Contract Violations: "Comparison Method Violates Its General Contract"

Build comparators from comparing and thenComparing rather than arithmetic; both failures here disappear.

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