你知道Enum怎么比较大小吗？

IntelliJ IDEA

java

Enum实现Comparable接口，可使用compareTo方法来比较大小先来个遍历enum的代码Code:package chapter4;/** * Created by MyWorld on 2016/3/21. */enum Season {    Spring,    Summer,    Autumn,    Winter}public class EnumCompare {    public static void main(String[] args) {        for (Season season : Season.values()) {            System.out.println(season + '  ' + season.ordinal());        }    }}

执行上面的代码看看结果：Spring  0Summer  1Autumn  2Winter  3

看到了没，每个枚举值都有一个ordinal()方法，这个方法的执行结果是返回一个数。这个数据是什么意义呢？看看源码呢源码：/**    * Returns the ordinal of this enumeration constant (its position    * in its enum declaration, where the initial constant is assigned    * an ordinal of zero).    *     * Most programmers will have no use for this method.  It is    * designed for use by sophisticated enum-based data structures, such    * as {@link java.util.EnumSet} and {@link java.util.EnumMap}.    *    * @return the ordinal of this enumeration constant    */   public final int ordinal() {          return ordinal;   }

直接使用枚举对象进行比较大小，就是使用这个值使用Compare比较大小Code:System.out.println('Compare to autumn:' + season.compareTo(Season.Autumn));

执行下，看看结果与预期的是否一致是一致的！！Output:Spring  0Compare to autumn:-2Summer  1Compare to autumn:-1Autumn  2Compare to autumn:0Winter  3Compare to autumn:1

既然有ordinal()方法，能不能使用==运算符呢改下代码Code:System.out.println('Compare to autumn:' + (season == Season.Autumn));

执行下，看看结果是否与预期一致一致的.枚举值之间是可以使用==来比较大小的Output:Spring  0Compare to autumn:-2Compare to autumn:falseSummer  1Compare to autumn:-1Compare to autumn:falseAutumn  2Compare to autumn:0Compare to autumn:trueWinter  3Compare to autumn:1Compare to autumn:false