Hello!
I have a question regarding the output generated by the javap disassembler.
Lets say we have the following two classes:
public class A {
public int x = 0;
public int getX() {
return x;
}
}
and
public class Test {
public static void main(String [] args) {
A a = new A() {
public int getX() {
return 1;
}
};
int x = a.getX();
}
}The output generated after running
javac -g A.java Test.java
and
javap -p -v -s A.class Test$1.class Test.class
is:
Classfile /home/stefan/Projects/javap-test/A.class
Last modified May 7, 2014; size 337 bytes
MD5 checksum c92d7af447fa7717520d721a44940eb3
Compiled from "A.java"
public class A
SourceFile: "A.java"
minor version: 0
major version: 51
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #4.#18 // java/lang/Object."<init>":()V
#2 = Fieldref #3.#19 // A.x:I
#3 = Class #20 // A
#4 = Class #21 // java/lang/Object
#5 = Utf8 x
#6 = Utf8 I
#7 = Utf8 <init>
#8 = Utf8 ()V
#9 = Utf8 Code
#10 = Utf8 LineNumberTable
#11 = Utf8 LocalVariableTable
#12 = Utf8 this
#13 = Utf8 LA;
#14 = Utf8 getX
#15 = Utf8 ()I
#16 = Utf8 SourceFile
#17 = Utf8 A.java
#18 = NameAndType #7:#8 // "<init>":()V
#19 = NameAndType #5:#6 // x:I
#20 = Utf8 A
#21 = Utf8 java/lang/Object
{
public int x;
Signature: I
flags: ACC_PUBLIC
public A();
Signature: ()V
flags: ACC_PUBLIC
Code:
stack=2, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: aload_0
5: iconst_0
6: putfield #2 // Field x:I
9: return
LineNumberTable:
line 1: 0
line 2: 4
LocalVariableTable:
Start Length Slot Name Signature
0 10 0 this LA;
public int getX();
Signature: ()I
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: getfield #2 // Field x:I
4: ireturn
LineNumberTable:
line 5: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this LA;
}
Classfile /home/stefan/Projects/javap-test/Test$1.class
Last modified May 7, 2014; size 406 bytes
MD5 checksum 997ccb68d293f425eed24512bc5fdbf9
Compiled from "Test.java"
final class Test$1 extends A
SourceFile: "Test.java"
EnclosingMethod: #18.#19 // Test.main
InnerClasses:
static #2; //class Test$1
minor version: 0
major version: 51
flags: ACC_FINAL, ACC_SUPER
Constant pool:
#1 = Methodref #3.#20 // A."<init>":()V
#2 = Class #21 // Test$1
#3 = Class #22 // A
#4 = Utf8 <init>
#5 = Utf8 ()V
#6 = Utf8 Code
#7 = Utf8 LineNumberTable
#8 = Utf8 LocalVariableTable
#9 = Utf8 this
#10 = Utf8
#11 = Utf8 InnerClasses
#12 = Utf8 LTest$1;
#13 = Utf8 getX
#14 = Utf8 ()I
#15 = Utf8 SourceFile
#16 = Utf8 Test.java
#17 = Utf8 EnclosingMethod
#18 = Class #23 // Test
#19 = NameAndType #24:#25 // main:([Ljava/lang/String;)V
#20 = NameAndType #4:#5 // "<init>":()V
#21 = Utf8 Test$1
#22 = Utf8 A
#23 = Utf8 Test
#24 = Utf8 main
#25 = Utf8 ([Ljava/lang/String;)V
{
Test$1();
Signature: ()V
flags:
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method A."<init>":()V
4: return
LineNumberTable:
line 4: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this LTest$1;
public int getX();
Signature: ()I
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: iconst_1
1: ireturn
LineNumberTable:
line 6: 0
LocalVariableTable:
Start Length Slot Name Signature
0 2 0 this LTest$1;
}
Classfile /home/stefan/Projects/javap-test/Test.class
Last modified May 7, 2014; size 495 bytes
MD5 checksum 5ef25a1fdb4c9483b7573a8c9a0c993a
Compiled from "Test.java"
public class Test
SourceFile: "Test.java"
InnerClasses:
static #2; //class Test$1
minor version: 0
major version: 51
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #6.#26 // java/lang/Object."<init>":()V
#2 = Class #27 // Test$1
#3 = Methodref #2.#26 // Test$1."<init>":()V
#4 = Methodref #28.#29 // A.getX:()I
#5 = Class #30 // Test
#6 = Class #31 // java/lang/Object
#7 = Utf8
#8 = Utf8 InnerClasses
#9 = Utf8 <init>
#10 = Utf8 ()V
#11 = Utf8 Code
#12 = Utf8 LineNumberTable
#13 = Utf8 LocalVariableTable
#14 = Utf8 this
#15 = Utf8 LTest;
#16 = Utf8 main
#17 = Utf8 ([Ljava/lang/String;)V
#18 = Utf8 args
#19 = Utf8 [Ljava/lang/String;
#20 = Utf8 a
#21 = Utf8 LA;
#22 = Utf8 x
#23 = Utf8 I
#24 = Utf8 SourceFile
#25 = Utf8 Test.java
#26 = NameAndType #9:#10 // "<init>":()V
#27 = Utf8 Test$1
#28 = Class #32 // A
#29 = NameAndType #33:#34 // getX:()I
#30 = Utf8 Test
#31 = Utf8 java/lang/Object
#32 = Utf8 A
#33 = Utf8 getX
#34 = Utf8 ()I
{
public Test();
Signature: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 1: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this LTest;
public static void main(java.lang.String[]);
Signature: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=3, args_size=1
0: new #2 // class Test$1
3: dup
4: invokespecial #3 // Method Test$1."<init>":()V
7: astore_1
8: aload_1
9: invokevirtual #4 // Method A.getX:()I
12: istore_2
13: return
LineNumberTable:
line 4: 0
line 10: 8
line 11: 13
LocalVariableTable:
Start Length Slot Name Signature
0 14 0 args [Ljava/lang/String;
8 6 1 a LA;
13 1 2 x I
}
The a.getX() call from the main method of class Test is translated into bytecode as invokevirtual #4, where #4 is a reference to the getX() method from class A. If I run the example, the getX() method from the anonymous class Test$1 gets invoked as expected. Shouldn't the index of invokevirtual be a reference to the getX() method from class Test$1?
