class TestAccessPrivateVar{
private int a = 1;
class MyInner{
/*
synthetic final TestAccessPrivateVar this$0
<init>(synthetic final TestAccessPrivateVar this$0) {
this.this$0 = this$0;
super();
}
*/
public void t(){
int b = a; // int b = TestAccessPrivateVar.access$000(this$0);
a++; // TestAccessPrivateVar.access$008(this$0)
a += 1; // TestAccessPrivateVar.access$012(this$0, 1);
}
}
/*
synthetic static int access$000(TestAccessPrivateVar x0) {
return x0.a;
}
synthetic static int access$008(TestAccessPrivateVar x0) {
return x0.a++;
}
synthetic static int access$012(TestAccessPrivateVar x0, int x1) {
return x0.a += x1;
}
*/
}
class Outer {
private Outer(){}
/*
synthetic <init>(com.test20.Outer$1 x0) {
this();
}
synthetic static class Outer$1 { }
要用这个新的类，因为怕与现有类冲突
*/
class AOuter extends Outer{
// 将下面的构造函数更改为如下形式：
/*
synthetic final Outer this$0
public <init>(synthetic final Outer this$0) {
this.this$0 = this$0
super();
}
*/
public AOuter(){
super(); // 将会更改为super(null)进行调用
}
}
}
package com.test19;
public class TestProtectedVar {
protected int a = 1;
}
package com.test20;
import com.test19.TestProtectedVar;
class Parent extends TestProtectedVar{
public String method1() {
return "";
}
}
class Sub extends Parent {
public String method1() {
return null;
}
class inner {
public void t() {
Sub.super.method1(); // Sub.access$001(this$0)
Sub.this.method1(); // this$0.method1()
int x = a; // int x = Sub.access$100(this$0)
int y = Sub.super.a; // int y = Sub.access$201(this$0)
}
}
/*
synthetic static String access$001(Sub x0) {
return x0.method1();
}
synthetic static int access$100(Sub x0) {
return x0.a;
}
// 下面的方法虽然与上面的body中代码一致，但是编号不一样
synthetic static int access$201(Sub x0) {
return x0.a;
}
*/
}
在内部类中获取外部类的私有变量，需要通过access method进行获取，举个例子，如下：
class TestAccessPrivateVar{
private int a = 1;
class MyInner{
public void t(){
int b = a; // Test03.access$000(this$0)
a += 1; // Test03.access$012(this$0, 1)
}
}
}
通过在线工具http://www.javadecompilers.com/ 对class文件进行反编译后，结果如下：
package com.test19;
class TestAccessPrivateVar {
private int a = 1;
TestAccessPrivateVar() { }
static /* synthetic */ int access$000(TestAccessPrivateVar testAccessPrivateVar) {
return testAccessPrivateVar.a;
}
static /* synthetic */ int access$012(TestAccessPrivateVar testAccessPrivateVar, int n) {
return testAccessPrivateVar.a += n;
}
} 反编译内部类后的源代码如下：
package com.test19;
class TestAccessPrivateVar$MyInner {
/*synthetic*/ final Test07 this$0
TestAccessPrivateVar$MyInner(TestAccessPrivateVar var1) {
this.this$0 = var1;
}
public void t() {
int var1 = TestAccessPrivateVar.access$000(this.this$0);
TestAccessPrivateVar.access$012(this.this$0, 1);
}
}
Classfile /C:/TestAccessPrivateVar.class
Last modified 2018-7-26; size 534 bytes
MD5 checksum db3dba90c37e7c304a98af3f9d4438b1
Compiled from "Test03.java"
class com.test19.TestAccessPrivateVar
SourceFile: "Test03.java"
InnerClasses:
#6= #5 of #3; //MyInner=class com/test19/TestAccessPrivateVar$MyInner of class com/test19/TestAccessPrivateVar
minor version: 0
major version: 51
flags: ACC_SUPER
Constant pool:
#1 = Fieldref #3.#20 // com/test19/TestAccessPrivateVar.a:I
#2 = Methodref #4.#21 // java/lang/Object."<init>":()V
#3 = Class #22 // com/test19/TestAccessPrivateVar
#4 = Class #23 // java/lang/Object
#5 = Class #24 // com/test19/TestAccessPrivateVar$MyInner
#6 = Utf8 MyInner
#7 = Utf8 InnerClasses
#8 = Utf8 a
#9 = Utf8 I
#10 = Utf8 <init>
#11 = Utf8 ()V
#12 = Utf8 Code
#13 = Utf8 LineNumberTable
#14 = Utf8 access$000
#15 = Utf8 (Lcom/test19/TestAccessPrivateVar;)I
#16 = Utf8 access$012
#17 = Utf8 (Lcom/test19/TestAccessPrivateVar;I)I
#18 = Utf8 SourceFile
#19 = Utf8 Test03.java
#20 = NameAndType #8:#9 // a:I
#21 = NameAndType #10:#11 // "<init>":()V
#22 = Utf8 com/test19/TestAccessPrivateVar
#23 = Utf8 java/lang/Object
#24 = Utf8 com/test19/TestAccessPrivateVar$MyInner
{
com.test19.TestAccessPrivateVar();
flags:
Code:
stack=2, locals=1, args_size=1
0: aload_0
1: invokespecial #2 // Method java/lang/Object."<init>":()V
4: aload_0
5: iconst_1
6: putfield #1 // Field a:I
9: return
LineNumberTable:
line 4: 0
line 5: 4
line 6: 9
static int access$000(com.test19.TestAccessPrivateVar);
flags: ACC_STATIC, ACC_SYNTHETIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: getfield #1 // Field a:I
4: ireturn
LineNumberTable:
line 4: 0
static int access$012(com.test19.TestAccessPrivateVar, int);
flags: ACC_STATIC, ACC_SYNTHETIC
Code:
stack=3, locals=2, args_size=2
0: aload_0
1: dup
2: getfield #1 // Field a:I
5: iload_1
6: iadd
7: dup_x1
8: putfield #1 // Field a:I
11: ireturn
LineNumberTable:
line 4: 0
}
Classfile /C:/TestAccessPrivateVar$MyInner.class
Last modified 2018-7-26; size 597 bytes
MD5 checksum faad0d2e11456029c49b2a821e94c67d
Compiled from "Test03.java"
class com.test19.TestAccessPrivateVar$MyInner
SourceFile: "Test03.java"
InnerClasses:
#23= #5 of #19; //MyInner=class com/test19/TestAccessPrivateVar$MyInner of class com/test19/TestAccessPrivateVar
minor version: 0
major version: 51
flags: ACC_SUPER
Constant pool:
#1 = Fieldref #5.#17 // com/test19/TestAccessPrivateVar$MyInner.this$0:Lcom/test19/TestAccessPrivateVar;
#2 = Methodref #6.#18 // java/lang/Object."<init>":()V
#3 = Methodref #19.#20 // com/test19/TestAccessPrivateVar.access$000:(Lcom/test19/TestAccessPrivateVar;)I
#4 = Methodref #19.#21 // com/test19/TestAccessPrivateVar.access$012:(Lcom/test19/TestAccessPrivateVar;I)I
#5 = Class #22 // com/test19/TestAccessPrivateVar$MyInner
#6 = Class #25 // java/lang/Object
#7 = Utf8 this$0
#8 = Utf8 Lcom/test19/TestAccessPrivateVar;
#9 = Utf8 <init>
#10 = Utf8 (Lcom/test19/TestAccessPrivateVar;)V
#11 = Utf8 Code
#12 = Utf8 LineNumberTable
#13 = Utf8 t
#14 = Utf8 ()V
#15 = Utf8 SourceFile
#16 = Utf8 Test03.java
#17 = NameAndType #7:#8 // this$0:Lcom/test19/TestAccessPrivateVar;
#18 = NameAndType #9:#14 // "<init>":()V
#19 = Class #26 // com/test19/TestAccessPrivateVar
#20 = NameAndType #27:#28 // access$000:(Lcom/test19/TestAccessPrivateVar;)I
#21 = NameAndType #29:#30 // access$012:(Lcom/test19/TestAccessPrivateVar;I)I
#22 = Utf8 com/test19/TestAccessPrivateVar$MyInner
#23 = Utf8 MyInner
#24 = Utf8 InnerClasses
#25 = Utf8 java/lang/Object
#26 = Utf8 com/test19/TestAccessPrivateVar
#27 = Utf8 access$000
#28 = Utf8 (Lcom/test19/TestAccessPrivateVar;)I
#29 = Utf8 access$012
#30 = Utf8 (Lcom/test19/TestAccessPrivateVar;I)I
{
final com.test19.TestAccessPrivateVar this$0;
flags: ACC_FINAL, ACC_SYNTHETIC
com.test19.TestAccessPrivateVar$MyInner(com.test19.TestAccessPrivateVar);
flags:
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: aload_1
2: putfield #1 // Field this$0:Lcom/test19/TestAccessPrivateVar;
5: aload_0
6: invokespecial #2 // Method java/lang/Object."<init>":()V
9: return
LineNumberTable:
line 6: 0
public void t();
flags: ACC_PUBLIC
Code:
stack=2, locals=2, args_size=1
0: aload_0
1: getfield #1 // Field this$0:Lcom/test19/TestAccessPrivateVar;
4: invokestatic #3 // Method com/test19/TestAccessPrivateVar.access$000:(Lcom/test19/TestAccessPrivateVar;)I
7: istore_1
8: aload_0
9: getfield #1 // Field this$0:Lcom/test19/TestAccessPrivateVar;
12: iconst_1
13: invokestatic #4 // Method com/test19/TestAccessPrivateVar.access$012:(Lcom/test19/TestAccessPrivateVar;I)I
16: pop
17: return
LineNumberTable:
line 8: 0
line 9: 8
line 10: 17
}