嵌套类的构造函数出现问题

首先，感谢您提出这个有趣的问题。我很感兴趣，以至于我忍不住要看一下字节码。这是字节码

TestNested

Compiled from "TestNested.java"  public class a.TestNested {    public a.TestNested();      Code:         0: aload_0     1: invokespecial #1       // Method java/lang/Object."<init>":()V         4: return    public static void main(java.lang.String[]);      Code:         0: ldc_w         #2       // class a/TestNested$A         3: astore_1    4: aload_1     5: invokevirtual #3       // Method java/lang/Class.getDeclaredConstructors:()[Ljava/lang/reflect/Constructor;         8: astore_2    9: aload_2    10: arraylength11: istore_3   12: iconst_0   13: istore        4        15: iload         4        17: iload_3    18: if_icmpge     41        21: aload_2    22: iload         4        24: aaload     25: astore        5        27: getstatic     #4       // Field java/lang/System.out:Ljava/io/PrintStream;        30: aload         5        32: invokevirtual #5       // Method java/io/PrintStream.println:(Ljava/lang/Object;)V        35: iinc          4, 1        38: goto          15        41: new#2       // class a/TestNested$A        44: dup        45: new#6       // class a/TestNested        48: dup        49: invokespecial #7       // Method "<init>":()V        52: dup        53: invokevirtual #8       // Method java/lang/Object.getClass:()Ljava/lang/Class;        56: pop        57: bipush        123        59: aconst_null60: invokespecial #9       // Method a/TestNested$A."<init>":(La/TestNested;ILa/TestNested$1;)V        63: astore_2   64: return          }

如您所见，构造函数

a.TestNested$A(a.TestNested,int,a.TestNested$1)

main

null

a.TestNested$1

因此，让我们看一下神秘的匿名类

a.TestNested$1

Compiled from "TestNested.java"class a.TestNested$1 {}

奇怪-我本来希望这堂课能真正做些事。要了解它，让我们看一下

a.TestNested$A

  a.TestNested$A(a.TestNested);    Code:       0: aload_0   1: aload_1   2: putfield      #2       // Field this$0:La/TestNested;       5: aload_0   6: invokespecial #3       // Method java/lang/Object."<init>":()V       9: return  private a.TestNested$A(a.TestNested, int);    Code:       0: aload_0   1: aload_1   2: putfield      #2       // Field this$0:La/TestNested;       5: aload_0   6: invokespecial #3       // Method java/lang/Object."<init>":()V       9: return  a.TestNested$A(a.TestNested, int, a.TestNested$1);    Code:       0: aload_0   1: aload_1   2: iload_2   3: invokespecial #1       // Method "<init>":(La/TestNested;I)V       6: return        }

查看包可见的构造函数

a.TestNested$A(a.TestNested, int, a.TestNested$1)

现在我们可以解释构造函数和匿名内部类。为了避免对私有构造函数的可见性限制，需要额外的构造函数。这个额外的构造函数只是委托给私有构造函数。但是，它不能具有与私有构造函数完全相同的签名。因此，添加了匿名内部类以提供唯一的签名，而不会与其他可能的重载构造函数发生冲突，例如带有署名

(int,int)

(int,Object)