User:Alexsmail/Computer programming/How Objects should be correctly compared in Java

Introduction

See appendix A for formal definition.

Method along consideration

equals()

Object hirerachy and its state (getClass() or instanceof ?). Immutable object. Object.equals()

hashCode()

Object.hashCode()

Natural order - compareTo()

Comparable#compareTo()

compareTo()

Comparable#compareTo()

Comparable#equals()

Combination consideration

equals() and hashCode()

Object.hashCode()

Maps, Hashtable and Set and Arrays

HashMap's and Set's key

Immutable. keys are Uniformly distributed.

Sort

QuickSort MergeSort Stable sort Comparator TreeMap

Miscellaneous

Sorting with Comparator

Arrays.sort()

Appendix B

Mathematic background

Set Order pair Relation Relation over Set Two-place relation function function in Java Partial Order Full order Equivalence relation Equivalence class