Java枚举是类.它们被编译为类.
下面的例子如何编译？
什么是“班级”？
什么是确切的类代码？我想要实际的Java代码.
public enum Ordinals {
FIRST("st"),SECOND("nd"),THIRD("rd");
private String notation;
private Ordinals(String notation) {
this.notation = notation;
}
public String getNotation() {
return notation;
}
}
解决方法
每个枚举类被编译为一个类,它是java.lang.Enum的子类.每个枚举常数成为该类内的静态最终常数.然后,以声明的顺序创建一个数组$VALUES,其中包含所有枚举常量.
您可以使用命令javap -p -c Ordinals(在编译的.class文件)上反汇编代码,以了解详细信息.
Compiled from "Ordinals.java"
public final class Ordinals extends java.lang.Enum<Ordinals> {
public static final Ordinals FIRST;
public static final Ordinals SECOND;
public static final Ordinals THIRD;
private java.lang.String notation; // your custom field
private static final Ordinals[] $VALUES; // all enum constants
public static Ordinals[] values(); // every enum class has this static method
Code:
0: getstatic #1 // Field $VALUES:[LOrdinals;
3: invokevirtual #2 // Method "[LOrdinals;".clone:()Ljava/lang/Object;
6: checkcast #3 // class "[LOrdinals;"
9: areturn
public static Ordinals valueOf(java.lang.String); // every enum class has this static method
Code:
0: ldc_w #4 // class Ordinals
3: aload_0
4: invokestatic #5 // Method java/lang/Enum.valueOf:(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Enum;
7: checkcast #4 // class Ordinals
10: areturn
private Ordinals(java.lang.String);
Code:
0: aload_0
1: aload_1
2: iload_2
3: invokespecial #6 // Method java/lang/Enum."<init>":(Ljava/lang/String;I)V
6: aload_0
7: aload_3
8: putfield #7 // Field notation:Ljava/lang/String;
11: return
public java.lang.String getNotation();
Code:
0: aload_0
1: getfield #7 // Field notation:Ljava/lang/String;
4: areturn
static {}; // fills the $VALUES array and initializes the static fields corresponding to the enum constants
Code:
0: new #4 // class Ordinals
3: dup
4: ldc #8 // String FIRST
6: iconst_0
7: ldc #9 // String st
9: invokespecial #10 // Method "<init>":(Ljava/lang/String;ILjava/lang/String;)V
12: putstatic #11 // Field FIRST:LOrdinals;
15: new #4 // class Ordinals
18: dup
19: ldc #12 // String SECOND
21: iconst_1
22: ldc #13 // String nd
24: invokespecial #10 // Method "<init>":(Ljava/lang/String;ILjava/lang/String;)V
27: putstatic #14 // Field SECOND:LOrdinals;
30: new #4 // class Ordinals
33: dup
34: ldc #15 // String THIRD
36: iconst_2
37: ldc #16 // String rd
39: invokespecial #10 // Method "<init>":(Ljava/lang/String;ILjava/lang/String;)V
42: putstatic #17 // Field THIRD:LOrdinals;
45: iconst_3
46: anewarray #4 // class Ordinals
49: dup
50: iconst_0
51: getstatic #11 // Field FIRST:LOrdinals;
54: aastore
55: dup
56: iconst_1
57: getstatic #14 // Field SECOND:LOrdinals;
60: aastore
61: dup
62: iconst_2
63: getstatic #17 // Field THIRD:LOrdinals;
66: aastore
67: putstatic #1 // Field $VALUES:[LOrdinals;
70: return
}
这将转换回Java
public final class Ordinals extends java.lang.Enum<Ordinals> {
public static final Ordinals FIRST;
public static final Ordinals SECOND;
public static final Ordinals THIRD;
private String notation;
private static final Ordinals[] $VALUES;
public static Ordinals[] values() {
return $VALUES.clone();
}
public static Ordinals valueOf(String name) {
return (Ordinals) Enum.valueOf(Ordinals.class,name);
}
private Ordinals(String name,int ordinal,String notation) {
super(name,ordinal);
this.notation = notation
}
static {
FIRST = new Ordinals("FIRST","st");
SECOND = new Ordinals("SECOND",1,"nd");
THIRD = new Ordinals("THIRD",2,"rd");
Ordinals[] $VALUES = new Ordinals[3];
$VALUES[0] = FIRST;
$VALUES[1] = SECOND;
$VALUES[2] = THIRD;
Ordinals.$VALUES = $VALUES;
}
}
类版本完全不相关 – 这取决于您使用的Java编译器的版本(或编译器上的显式设置,以强制其编译为较旧的Java版本).
