内部方法中的匿名内部类 [英] Anonymous Inner Classes Inside Methods

问题描述

请查看以下代码：

import java.util.ArrayList;
import java.util.List;

class Main{
     public static <T> List<T> modifiedList(final List<T> list){
         return new ArrayList<T>(){
            @Override
             public boolean add(T element){
                 super.add(element);
                 return list.add(element);
             }
         };
    }

     public static void main(String[] args) {
         List<String> originalList=new ArrayList<String>();
         List<String> duplicateList=modifiedList(originalList);
         originalList.add("1");
         originalList.add("2");
         originalList.add("3");
         System.out.println(originalList+" "+duplicateList);
         duplicateList.add("4");
         duplicateList.add("5");
         duplicateList.add("6");
         System.out.println(originalList+" "+duplicateList);
     }

在上面的代码中，在方法中声明的匿名内部类的实例modifiedList（）能够访问传递给该方法的参数。 AFAIK Java为内部类创建一个单独的字节码文件。

In the above code, the instance of an anonymous inner class declared in the method modifiedList() is able to access the parameter passed to that method. AFAIK Java creates a separate bytecode file for inner classes.

任何人都可以解释Java在字节码级别如何处理这些局部变量绑定？我的意思是，Java如何跟踪作为参数传递给该方法的对象的引用？

Can anyone explain how these local variable bindings are handled by Java at the bytecode level? I mean, how exactly does Java keep track of the reference to the object passed as a parameter to that method?

任何帮助都将非常感谢！

Any help would be greatly appreciated!

[抱歉我的英语不好！如果您理解我的问题，请编辑此帖并删除语法错误。谢谢！]

推荐答案

基本上代码由编译器重写（注意我没有尝试编译它......，可能有错误）：

Essentially the code is rewritten by the complier as (note I didn't try to compile it..., might have errors):

class Main$1<T>
    extends ArrayList<T>
{
    private final List<T> list;

    Main$1(final List<T> a)
    {
        list = a;
    }

    @Override
    public boolean add(T element)
    {
        super.add(element);
        return list.add(element);
    }
}

和

class Main{
     public static <T> List<T> modifiedList(final List<T> list)
     {
         return new Main$1<T>(list);
     }

     public static void main(String[] args) 
     {
         List<String> originalList=new ArrayList<String>();
         List<String> duplicateList=modifiedList(originalList);
         originalList.add("1");
         originalList.add("2");
         originalList.add("3");
         System.out.println(originalList+" "+duplicateList);
         duplicateList.add("4");
         duplicateList.add("5");
         duplicateList.add("6");
         System.out.println(originalList+" "+duplicateList);
     }

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