[Java]枚举

用法

enum Color {
    RED,
    GREEN
}

enum Color {
    RED("red"),
    GREEN("green");

    String name;

    Color(String name) {
        this.name = name;
    }
    
    public String toString(){
        return name;
    }
}

enum Color implements Comparable<Color> {
    RED,
    GREEN;
}

        Color c = Color.RED;
        if(c == Color.GREEN){
            // ...
        }

        Color c = Color.RED;
        switch (c) {
            case RED:
            case GREEN:
        }

        for (Color c : Color.values()) {
            System.out.println(c);
        }

System.out.println(Color.valueOf("RED"));

枚举VS常量

    public static void check(Color c){
        
    }

enum到底是什么

final class Color extends java.lang.Enum implements java.lang.Comparable{
	public static final Color RED;
	public static final Color GREEN;
	public static Color[] values();
	public static Color valueOf(java.lang.String);
	static {};
}

java.lang.Enum

然后通过javap -c Color来看初始化的代码：

static {};
  Code:
   0:   new     #4; //class Color
   3:   dup
   4:   ldc     #7; //String RED
   6:   iconst_0
   7:   invokespecial   #8; //Method "<init>":(Ljava/lang/String;I)V
   10:  putstatic       #9; //Field RED:LColor;
   13:  new     #4; //class Color
   16:  dup
   17:  ldc     #10; //String GREEN
   19:  iconst_1
   20:  invokespecial   #8; //Method "<init>":(Ljava/lang/String;I)V
   23:  putstatic       #11; //Field GREEN:LColor;
   26:  iconst_2
   27:  anewarray       #4; //class Color
   30:  dup
   31:  iconst_0
   32:  getstatic       #9; //Field RED:LColor;
   35:  aastore
   36:  dup
   37:  iconst_1
   38:  getstatic       #11; //Field GREEN:LColor;
   41:  aastore
   42:  putstatic       #1; //Field $VALUES:[LColor;
   45:  return

这里大家可能会对枚举switch有疑问，我们写代码来看下：

public class Test {
    public void func(Color c){
        switch(c){
            case RED:
            case GREEN:
        }
    }
}

public void func(Color);
  Code:
   0:   getstatic       #2; //Field Test$1.$SwitchMap$Color:[I
   3:   aload_1
   4:   invokevirtual   #3; //Method Color.ordinal:()I
   7:   iaload
   8:   lookupswitch{ //2
                1: 36;
                2: 36;
                default: 36 }
   36:  return

}

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[Java]枚举

原文：http://blog.csdn.net/wszt_gzt/article/details/33719009