Comparable.compareTo的返回值在Java中意味着什么？

本文介绍了Comparable.compareTo的返回值在Java中意味着什么？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 返回 0 ，返回 1 并返回 -1 中的/ code> Java中的 compareTo（） ？What is the difference between returning 0, returning 1 and returning -1 in compareTo() in Java?推荐答案 官方定义 来自 Comparable.compareTo（T）： 将此对象与订单的指定对象。返回负整数，零或正整数，因为此对象小于等于或大于指定对象。 Compares this object with the specified object for order. Returns a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object.对于所有x和y，实现者必须确保 sgn（x.compareTo（y））== -sgn（y.compareTo（x））。 （这意味着x.compareTo（y）必须抛出异常iff y.compareTo（x）抛出异常。）The implementor must ensure sgn(x.compareTo(y)) == -sgn(y.compareTo(x)) for all x and y. (This implies that x.compareTo(y) must throw an exception iff y.compareTo(x) throws an exception.)实现者还必须确保关系是可传递的：（x.compareTo（y）> 0& y.compareTo（z）> 0）表示x.compareTo（z ）> 0。The implementor must also ensure that the relation is transitive: (x.compareTo(y)>0 && y.compareTo(z)>0) implies x.compareTo(z)>0.最后，实现者必须确保 x.compareTo（y）== 0意味着 sgn（x.compareTo） （z））== sgn（y.compareTo（z）），对于所有z。Finally, the implementor must ensure that x.compareTo(y)==0 implies that sgn(x.compareTo(z)) == sgn(y.compareTo(z)), for all z.强烈建议，但不是严格要求（x.compareTo（y）== 0）==（x.equals（y））。 一般来说，任何的类都会实现Comparable接口，如果清楚地表明这一事实，则违反了这个条件。 推荐的语言是注意：这个类的自然顺序是与equals不一致。It is strongly recommended, but not strictly required that (x.compareTo(y)==0) == (x.equals(y)). Generally speaking, any class that implements the Comparable interface and violates this condition should clearly indicate this fact. The recommended language is "Note: this class has a natural ordering that is inconsistent with equals."在上述描述，表示法sgn（表达式）指定数学符号函数，定义为返回-1， 0或1中的一个，具体取决于值表达式为负数，零或为正。In the foregoing description, the notation sgn(expression) designates the mathematical signum function, which is defined to return one of -1, 0, or 1 according to whether the value of expression is negative, zero or positive. 我的版本 简而言之：My VersionIn short:this.compareTo(that)返回 负数如果这个<那 0 如果这= =那 一个正整数如果这个>那个 a negative int if this < that0 if this == thata positive int if this > that此方法的实现确定< > 和 == （我的意思是 == 在java的对象标识运算符意义上）where the implementation of this method determines the actual semantics of < > and == (I don't mean == in the sense of java's object identity operator)"abc".compareTo("def")将产生小于0的值 abc 按字母顺序排在 def 之前。will yield something smaller than 0 as abc is alphabetically before def.Integer.valueOf(2).compareTo(Integer.valueOf(1))会产生一些东西大于0，因为2大于1. will yield something larger than 0 because 2 is larger than 1. 注意：对于实现Comparable的类来说，在javadocs中声明它的compareTo（）方法的语义是一种好习惯。Note: It is good practice for a class that implements Comparable to declare the semantics of it's compareTo() method in the javadocs. 注意： ÿ你应该至少阅读下列之一：Note: you should read at least one of the following: 对象订购部分 Sun Trail中的Collection Trail 教程 有效Java Joshua Bloch，特别是项目12： 考虑实施可比较 Java Generics and Collections by Maurice Naftalin，Philip Wadler，第3.1章：可比较 the Object Ordering section ofthe Collection Trail in the Sun JavaTutorialEffective Java byJoshua Bloch, especially item 12:Consider implementing ComparableJava Generics and Collections byMaurice Naftalin, Philip Wadler, chapter 3.1: Comparable 警告：你永远不应该依赖compareTo的返回值 -1 ， 0 和 1 。你应该总是测试 x< 0 ， x == 0 ， x> 0 ，分别为。Warning: you should never rely on the return values of compareTo being -1, 0 and 1. You should always test for x < 0, x == 0, x > 0, respectively. 这篇关于Comparable.compareTo的返回值在Java中意味着什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！