Attr的visitNewClass()方法解读
在visitNewClass()方法中有如下注释：
We are seeing an anonymous class instance creation.
In this case, the class instance creation expression
E.new <typeargs1>C<typargs2>(args) { ... }
is represented internally as
E . new <typeargs1>C<typargs2>(args) ( class <empty-name> { ... } ) .
This expression is then *transformed* as follows:
(1) add a STATIC flag to the class definition if the current environment is static
(2) add an extends or implements clause
(3) add a constructor.
For instance, if C is a class, and ET is the type of E, the expression
E.new <typeargs1>C<typargs2>(args) { ... }
is translated to (where X is a fresh name and typarams is the
parameter list of the super constructor):
new <typeargs1>X(<*nullchk*>E, args)
where
X extends C<typargs2> {
<typarams> X(ET e, args) {
e.<typeargs1>super(args)
}
...
}
举个例子，如下：
class E{
class C<T1>{
// C的构造函数
public <T2> C(){ }
public void t(){
E e = new E();
e.new <String>C<Integer>(){};
}
}
}
按如上的描述，应该被改写为：
class E{
class C<T1>{
// C的构造函数
public <T2> C(){ }
public void t(){
E e = new E();
new <String>X(e); // 更改为了这样的形式
}
}
}
class X extends E.C<Integer>{
<T2> X(E e){
e.<T2>super();
}
}
传入visitNewClass()方法的tree参数如下截图。
通过调用visitNewClass()方法后，e.new <String>C<Integer>(){}方法被改写为：
new <String>C<Integer>(e<*nullchk*>){
<T2 extends java.lang.Object>(com.test19.E x0) {
x0.<T2>super();
}
}
编译后生成3个Class文件，如下：
（1）E.class，通过调用Attr类的visitNewClass()方法后，e.new <String>C<Integer>(){}方法被改写为：
class E {
E() {
super();
}
class C<T1> {
public <T2>C() {
super();
}
public void t() {
E e = new E();
new <String>C<Integer>(e<*nullchk*>){
<T2 extends .java.lang.Object>(.com.test19.E x0) {
x0.<T2>super();
}
};
}
}
}
最终的字节码如下：
class com.test19.E
SourceFile: "Test07.java"
InnerClasses:
#5= #4 of #2; //C=class com/test19/E$C of class com/test19/E
minor version: 0
major version: 51
flags: ACC_SUPER
Constant pool:
#1 = Methodref #3.#16 // java/lang/Object."<init>":()V
#2 = Class #17 // com/test19/E
#3 = Class #18 // java/lang/Object
#4 = Class #19 // com/test19/E$C
#5 = Utf8 C
#6 = Utf8 InnerClasses
#7 = Utf8 <init>
#8 = Utf8 ()V
#9 = Utf8 Code
#10 = Utf8 LineNumberTable
#11 = Utf8 LocalVariableTable
#12 = Utf8 this
#13 = Utf8 Lcom/test19/E;
#14 = Utf8 SourceFile
#15 = Utf8 Test07.java
#16 = NameAndType #7:#8 // "<init>":()V
#17 = Utf8 com/test19/E
#18 = Utf8 java/lang/Object
#19 = Utf8 com/test19/E$C
{
com.test19.E();
flags:
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 4: 0
line 5: 4
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this Lcom/test19/E;
}
（2）E$C通过调用desugar类后如下：
class E$C {
/*synthetic*/ final E this$0;
public E$C(/*synthetic*/ final E this$0) {
this.this$0 = this$0;
super();
}
public void t() {
E e = new E();
new <String>E$C$1(this, e<*nullchk*>);
}
}
最终的字节码如下：
class com.test19.E$C<T1 extends java.lang.Object> extends java.lang.Object
Signature: #29 // <T1:Ljava/lang/Object;>Ljava/lang/Object;
SourceFile: "Test07.java"
InnerClasses:
#10= #8 of #3; //C=class com/test19/E$C of class com/test19/E
#5; //class com/test19/E$C$1
minor version: 0
major version: 51
flags: ACC_SUPER
Constant pool:
#1 = Fieldref #8.#32 // com/test19/E$C.this$0:Lcom/test19/E;
#2 = Methodref #9.#33 // java/lang/Object."<init>":()V
#3 = Class #34 // com/test19/E
#4 = Methodref #3.#33 // com/test19/E."<init>":()V
#5 = Class #35 // com/test19/E$C$1
#6 = Methodref #9.#36 // java/lang/Object.getClass:()Ljava/lang/Class;
#7 = Methodref #5.#37 // com/test19/E$C$1."<init>":(Lcom/test19/E$C;Lcom/test19/E;)V
#8 = Class #38 // com/test19/E$C
#9 = Class #39 // java/lang/Object
#10 = Utf8 C
#11 = Utf8 InnerClasses
#12 = Utf8
#13 = Utf8 this$0
#14 = Utf8 Lcom/test19/E;
#15 = Utf8 <init>
#16 = Utf8 (Lcom/test19/E;)V
#17 = Utf8 Code
#18 = Utf8 LineNumberTable
#19 = Utf8 LocalVariableTable
#20 = Utf8 this
#21 = Utf8 Lcom/test19/E$C;
#22 = Utf8 LocalVariableTypeTable
#23 = Utf8 Lcom/test19/E$C<TT1;>;
#24 = Utf8 Signature
#25 = Utf8 <T2:Ljava/lang/Object;>()V
#26 = Utf8 t
#27 = Utf8 ()V
#28 = Utf8 e
#29 = Utf8 <T1:Ljava/lang/Object;>Ljava/lang/Object;
#30 = Utf8 SourceFile
#31 = Utf8 Test07.java
#32 = NameAndType #13:#14 // this$0:Lcom/test19/E;
#33 = NameAndType #15:#27 // "<init>":()V
#34 = Utf8 com/test19/E
#35 = Utf8 com/test19/E$C$1
#36 = NameAndType #40:#41 // getClass:()Ljava/lang/Class;
#37 = NameAndType #15:#42 // "<init>":(Lcom/test19/E$C;Lcom/test19/E;)V
#38 = Utf8 com/test19/E$C
#39 = Utf8 java/lang/Object
#40 = Utf8 getClass
#41 = Utf8 ()Ljava/lang/Class;
#42 = Utf8 (Lcom/test19/E$C;Lcom/test19/E;)V
{
final com.test19.E this$0;
flags: ACC_FINAL, ACC_SYNTHETIC
public <T2 extends java/lang/Object> com.test19.E$C();
flags: ACC_PUBLIC
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: aload_1
2: putfield #1 // Field this$0:Lcom/test19/E;
5: aload_0
6: invokespecial #2 // Method java/lang/Object."<init>":()V
9: return
LineNumberTable:
line 7: 0
LocalVariableTable:
Start Length Slot Name Signature
0 10 0 this Lcom/test19/E$C;
LocalVariableTypeTable:
Start Length Slot Name Signature
0 10 0 this Lcom/test19/E$C<TT1;>;
Signature: #25 // <T2:Ljava/lang/Object;>()V
public void t();
flags: ACC_PUBLIC
Code:
stack=5, locals=2, args_size=1
0: new #3 // class com/test19/E
3: dup
4: invokespecial #4 // Method com/test19/E."<init>":()V
7: astore_1
8: new #5 // class com/test19/E$C$1
11: dup
12: aload_0
13: aload_1
14: dup
15: invokevirtual #6 // Method java/lang/Object.getClass:()Ljava/lang/Class;
18: pop
19: invokespecial #7 // Method com/test19/E$C$1."<init>":(Lcom/test19/E$C;Lcom/test19/E;)V
22: pop
23: return
LineNumberTable:
line 10: 0
line 11: 8
line 12: 23
LocalVariableTable:
Start Length Slot Name Signature
0 24 0 this Lcom/test19/E$C;
8 16 1 e Lcom/test19/E;
LocalVariableTypeTable:
Start Length Slot Name Signature
0 24 0 this Lcom/test19/E$C<TT1;>;
}
（3）E$C$1通过调用desugar类后代码如下：
class E$C$1 extends com.test19.E$C {
/*synthetic*/ final E$C this$1;
E$C$1(/*synthetic*/ final E$C this$1, com.test19.E x0) {
this.this$1 = this$1;
<T2>super(x0<*nullchk*>);
}
}
最终编译后的字节码如下：
class com.test19.E$C$1 extends com.test19.E$C<java.lang.Integer>
Signature: #23 // Lcom/test19/E$C<Ljava/lang/Integer;>;
SourceFile: "Test07.java"
EnclosingMethod: #5.#27 // com.test19.E$C.t
InnerClasses:
#7= #5 of #33; //C=class com/test19/E$C of class com/test19/E
#4; //class com/test19/E$C$1
minor version: 0
major version: 51
flags: ACC_SUPER
Constant pool:
#1 = Fieldref #4.#28 // com/test19/E$C$1.this$1:Lcom/test19/E$C;
#2 = Methodref #29.#30 // java/lang/Object.getClass:()Ljava/lang/Class;
#3 = Methodref #5.#31 // com/test19/E$C."<init>":(Lcom/test19/E;)V
#4 = Class #32 // com/test19/E$C$1
#5 = Class #34 // com/test19/E$C
#6 = Utf8 this$1
#7 = Utf8 C
#8 = Utf8 InnerClasses
#9 = Utf8 Lcom/test19/E$C;
#10 = Utf8 <init>
#11 = Utf8 (Lcom/test19/E$C;Lcom/test19/E;)V
#12 = Utf8 Code
#13 = Utf8 LineNumberTable
#14 = Utf8 LocalVariableTable
#15 = Utf8 this
#16 = Utf8
#17 = Utf8 Lcom/test19/E$C$1;
#18 = Utf8 x0
#19 = Utf8 Lcom/test19/E;
#20 = Utf8 LocalVariableTypeTable
#21 = Utf8 Lcom/test19/E$C.1;
#22 = Utf8 Signature
#23 = Utf8 Lcom/test19/E$C<Ljava/lang/Integer;>;
#24 = Utf8 SourceFile
#25 = Utf8 Test07.java
#26 = Utf8 EnclosingMethod
#27 = NameAndType #35:#36 // t:()V
#28 = NameAndType #6:#9 // this$1:Lcom/test19/E$C;
#29 = Class #37 // java/lang/Object
#30 = NameAndType #38:#39 // getClass:()Ljava/lang/Class;
#31 = NameAndType #10:#40 // "<init>":(Lcom/test19/E;)V
#32 = Utf8 com/test19/E$C$1
#33 = Class #41 // com/test19/E
#34 = Utf8 com/test19/E$C
#35 = Utf8 t
#36 = Utf8 ()V
#37 = Utf8 java/lang/Object
#38 = Utf8 getClass
#39 = Utf8 ()Ljava/lang/Class;
#40 = Utf8 (Lcom/test19/E;)V
#41 = Utf8 com/test19/E
{
final com.test19.E$C this$1;
flags: ACC_FINAL, ACC_SYNTHETIC
com.test19.E$C$1(com.test19.E$C, com.test19.E);
flags:
Code:
stack=3, locals=3, args_size=3
0: aload_0
1: aload_1
2: putfield #1 // Field this$1:Lcom/test19/E$C;
5: aload_0
6: aload_2
7: dup
8: invokevirtual #2 // Method java/lang/Object.getClass:()Ljava/lang/Class;
11: pop
12: invokespecial #3 // Method com/test19/E$C."<init>":(Lcom/test19/E;)V
15: return
LineNumberTable:
line 11: 0
LocalVariableTable:
Start Length Slot Name Signature
0 16 0 this Lcom/test19/E$C$1;
0 16 2 x0 Lcom/test19/E;
LocalVariableTypeTable:
Start Length Slot Name Signature
0 16 0 this Lcom/test19/E$C.1;
}
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