在java中，这样的枚举类型编译成什么？

enums java enumeration java-8

2022-09-03 06:36:08

下面是定义枚举类型的代码。

enum Company{
    EBAY(30), PAYPAL(10), GOOGLE(15), YAHOO(20), ATT(25);
    private int value;

    private Company(int value){
        super(this.name()); 
        this.value = value;
    }

    public int getValue(){
        return value;
    }
}

在内部编译为，

final class Company extends Enum<Company>{
    public final static Company EBAY = new Company(30);
    public final static Company PAYPAL = new Company(10);
    public final static Company GOOGLE = new Company(15);
    public final static Company YAHOO = new Company(20);
    public final static Company ATT = new Company(25);

    private int value;

    private Company(int value){
        super(this.name(),Enum.valueOf(Company.class, this.name()));
        this.value = value;
    }

    public int getValue(){
        return value;
    }
}

我的理解是否正确？

答案 1

从功能上讲，是的。从字面上看，没有（你不能为一件事明确地子类）。有一个 .而你的无效代码（你不能调用），需要一个返回类型。Enumenum(s)toStringenumsuper()getValue

enum Company{
    EBAY(30), PAYPAL(10), GOOGLE(15), YAHOO(20), ATT(25);
    private int value;

    private Company(int value){
        this.value = value;
    }

    public int getValue(){
        return value;
    }
}

答案 2

如果你删除了对它的调用是非法的，并且作为参数对super也是非法的，编译它并在类上运行javap，这是输出：superthis.name

$ /usr/lib/jvm/java-7-oracle/bin/javap -p Company.class 
Compiled from "Company.java"
final class Company extends java.lang.Enum<Company> {
  public static final Company EBAY;
  public static final Company PAYPAL;
  public static final Company GOOGLE;
  public static final Company YAHOO;
  public static final Company ATT;
  private int value;
  private static final Company[] $VALUES;
  public static Company[] values();
  public static Company valueOf(java.lang.String);
  private Company(int);
  public int getValue();
  static {};
}

这是静态的字节码，其中一部分

static {};
  flags: ACC_STATIC
  LineNumberTable:
    line 2: 0
    line 1: 75
  Code:
    stack=5, locals=0, args_size=0
       0: new           #4                  // class Company
       3: dup           
       4: ldc           #8                  // String EBAY
       6: iconst_0      
       7: bipush        30
       9: invokespecial #9                  // Method "<init>":(Ljava/lang/String;II)V
      12: putstatic     #10                 // Field EBAY:LCompany;