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Default methods#26

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Arneball wants to merge 1 commit intoluontola:masterfrom
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Default methods#26
Arneball wants to merge 1 commit intoluontola:masterfrom
Arneball:master

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@Arneball
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@Arneball Arneball commented Aug 11, 2014

public interface MyInterface {
default String def() {
return "[" + toString() + ", " + "def]";
}

default String join(MyInterface other) {
    return def() + other.def();
}

}

class C implements MyInterface{} compiles to:

public class testpackage.MyClass implements testpackage.MyInterface {
public testpackage.MyClass();
Code:
0: aload_0
1: invokespecial #16 // Method java/lang/Object."":()V
4: return

public java.lang.String join(testpackage.MyInterface);
Code:
0: aload_0
1: aload_1
2: invokestatic #46 // Method testpackage/MyInterfacehelper.join:(Ltestpackage/MyInterface;Ltestpackage/MyInterface;)Ljava/lang/String;
5: areturn

public java.lang.String def();
Code:
0: aload_0
1: invokestatic #49 // Method testpackage/MyInterfacehelper.def:(Ltestpackage/MyInterface;)Ljava/lang/String;
4: areturn
}

Where testpackage.MyInterfacehelper is compiled to
public class testpackage.MyInterfacehelper {
private testpackage.MyInterfacehelper();
Code:
0: aload_0
1: invokespecial #9 // Method java/lang/Object."":()V
4: return

public static java.lang.String def(testpackage.MyInterface);
Code:
0: new #13 // class java/lang/StringBuilder
3: dup
4: invokespecial #14 // Method java/lang/StringBuilder."":()V
7: ldc #16 // String [
9: invokevirtual #20 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
12: aload_0
13: invokevirtual #24 // Method java/lang/Object.toString:()Ljava/lang/String;
16: invokevirtual #20 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
19: ldc #26 // String ,
21: invokevirtual #20 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
24: ldc #28 // String def]
26: invokevirtual #20 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
29: invokevirtual #29 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
32: areturn

public static java.lang.String join(testpackage.MyInterface, testpackage.MyInterface);
Code:
0: new #13 // class java/lang/StringBuilder
3: dup
4: invokespecial #14 // Method java/lang/StringBuilder."":()V
7: aload_0
8: invokeinterface #35, 1 // InterfaceMethod testpackage/MyInterface.def:()Ljava/lang/String;
13: invokevirtual #20 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
16: aload_1
17: invokeinterface #35, 1 // InterfaceMethod testpackage/MyInterface.def:()Ljava/lang/String;
22: invokevirtual #20 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
25: invokevirtual #29 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
28: areturn
}

interface StaticTest {
static T staticMethod(T t) {
return t;
}
}
compiles to
public class testpackage.StaticTesthelper {
private testpackage.StaticTesthelper();
Code:
0: aload_0
1: invokespecial #9 // Method java/lang/Object."":()V
4: return

public static T staticMethod$static(T);
Code:
0: aload_0
1: areturn
}

Brigde methods are generated properly in example:
public interface BridgeParent {
T get();
}
public interface StringBridges extends BridgeParent {
@OverRide
default String get() {
return "default method";
}

default String concrete() {
    return "concrete";
}

}
public class testpackage.StringBridgeshelper
SourceFile: "testpackage/StringBridges.java"
minor version: 0
major version: 50
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Utf8 testpackage/StringBridgeshelper
#2 = Class #1 // testpackage/StringBridgeshelper
#3 = Utf8 java/lang/Object
#4 = Class #3 // java/lang/Object
#5 = Utf8 testpackage/StringBridges.java
#6 = Utf8
#7 = Utf8 ()V
#8 = NameAndType #6:#7 // "":()V
#9 = Methodref #4.#8 // java/lang/Object."":()V
#10 = Utf8 get
#11 = Utf8 (Ltestpackage/StringBridges;)Ljava/lang/String;
#12 = Utf8 default method
#13 = String #12 // default method
#14 = Utf8 concrete
#15 = String #14 // concrete
#16 = Utf8 (Ltestpackage/StringBridges;)Ljava/lang/Object;
#17 = Utf8 testpackage/StringBridges
#18 = Class #17 // testpackage/StringBridges
#19 = Utf8 ()Ljava/lang/String;
#20 = NameAndType #10:#19 // get:()Ljava/lang/String;
#21 = InterfaceMethodref #18.#20 // testpackage/StringBridges.get:()Ljava/lang/String;
#22 = Utf8 Code
#23 = Utf8 LineNumberTable
#24 = Utf8 SourceFile
{
private testpackage.StringBridgeshelper();
descriptor: ()V
flags: ACC_PRIVATE
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #9 // Method java/lang/Object."":()V
4: return

public static java.lang.String get(testpackage.StringBridges);
descriptor: (Ltestpackage/StringBridges;)Ljava/lang/String;
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=1, locals=1, args_size=1
0: ldc #13 // String default method
2: areturn
LineNumberTable:
line 9: 0

public static java.lang.String concrete(testpackage.StringBridges);
descriptor: (Ltestpackage/StringBridges;)Ljava/lang/String;
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=1, locals=1, args_size=1
0: ldc #15 // String concrete
2: areturn
LineNumberTable:
line 13: 0

public static java.lang.Object get(testpackage.StringBridges);
descriptor: (Ltestpackage/StringBridges;)Ljava/lang/Object;
flags: ACC_PUBLIC, ACC_STATIC, ACC_BRIDGE, ACC_SYNTHETIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokeinterface #21, 1 // InterfaceMethod testpackage/StringBridges.get:()Ljava/lang/String;
6: areturn
LineNumberTable:
line 6: 0
}

@Arneball
package testpackage;
8e13c80 
public interface MyInterface {
    default String def() {
        return "[" + toString() + ", " + "def]";
    }

    default String join(MyInterface other) {
        return def() + other.def();
    }
}

class C implements MyInterface{}  compiles to:

public class testpackage.MyClass implements testpackage.MyInterface {
  public testpackage.MyClass();
    Code:
       0: aload_0
       1: invokespecial luontola#16                 // Method java/lang/Object."<init>":()V
       4: return

  public java.lang.String join(testpackage.MyInterface);
    Code:
       0: aload_0
       1: aload_1
       2: invokestatic  luontola#46                 // Method testpackage/MyInterfacehelper.join:(Ltestpackage/MyInterface;Ltestpackage/MyInterface;)Ljava/lang/String;
       5: areturn

  public java.lang.String def();
    Code:
       0: aload_0
       1: invokestatic  luontola#49                 // Method testpackage/MyInterfacehelper.def:(Ltestpackage/MyInterface;)Ljava/lang/String;
       4: areturn
}

Where testpackage.MyInterfacehelper is compiled to
public class testpackage.MyInterfacehelper {
  private testpackage.MyInterfacehelper();
    Code:
       0: aload_0
       1: invokespecial luontola#9                  // Method java/lang/Object."<init>":()V
       4: return

  public static java.lang.String def(testpackage.MyInterface);
    Code:
       0: new           luontola#13                 // class java/lang/StringBuilder
       3: dup
       4: invokespecial luontola#14                 // Method java/lang/StringBuilder."<init>":()V
       7: ldc           luontola#16                 // String [
       9: invokevirtual luontola#20                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      12: aload_0
      13: invokevirtual luontola#24                 // Method java/lang/Object.toString:()Ljava/lang/String;
      16: invokevirtual luontola#20                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      19: ldc           luontola#26                 // String ,
      21: invokevirtual luontola#20                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      24: ldc           luontola#28                 // String def]
      26: invokevirtual luontola#20                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      29: invokevirtual luontola#29                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      32: areturn

  public static java.lang.String join(testpackage.MyInterface, testpackage.MyInterface);
    Code:
       0: new           luontola#13                 // class java/lang/StringBuilder
       3: dup
       4: invokespecial luontola#14                 // Method java/lang/StringBuilder."<init>":()V
       7: aload_0
       8: invokeinterface luontola#35,  1           // InterfaceMethod testpackage/MyInterface.def:()Ljava/lang/String;
      13: invokevirtual luontola#20                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      16: aload_1
      17: invokeinterface luontola#35,  1           // InterfaceMethod testpackage/MyInterface.def:()Ljava/lang/String;
      22: invokevirtual luontola#20                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      25: invokevirtual luontola#29                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      28: areturn
}

==============
interface StaticTest {
    static <T> T staticMethod(T t) {
        return t;
    }
}
compiles to
public class testpackage.StaticTesthelper {
  private testpackage.StaticTesthelper();
    Code:
       0: aload_0
       1: invokespecial luontola#9                  // Method java/lang/Object."<init>":()V
       4: return

  public static <T> T staticMethod$static(T);
    Code:
       0: aload_0
       1: areturn
}

========

Brigde methods are generated properly in example:
public interface BridgeParent<T> {
    T get();
}
public interface StringBridges extends BridgeParent<String> {
    @OverRide
    default String get() {
        return "default method";
    }

    default String concrete() {
        return "concrete";
    }
}
public class testpackage.StringBridgeshelper
  SourceFile: "testpackage/StringBridges.java"
  minor version: 0
  major version: 50
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   luontola#1 = Utf8               testpackage/StringBridgeshelper
   luontola#2 = Class              luontola#1             //  testpackage/StringBridgeshelper
   luontola#3 = Utf8               java/lang/Object
   luontola#4 = Class              luontola#3             //  java/lang/Object
   luontola#5 = Utf8               testpackage/StringBridges.java
   luontola#6 = Utf8               <init>
   luontola#7 = Utf8               ()V
   luontola#8 = NameAndType        luontola#6:luontola#7          //  "<init>":()V
   luontola#9 = Methodref          luontola#4.luontola#8          //  java/lang/Object."<init>":()V
  luontola#10 = Utf8               get
  luontola#11 = Utf8               (Ltestpackage/StringBridges;)Ljava/lang/String;
  luontola#12 = Utf8               default method
  luontola#13 = String             luontola#12            //  default method
  luontola#14 = Utf8               concrete
  luontola#15 = String             luontola#14            //  concrete
  luontola#16 = Utf8               (Ltestpackage/StringBridges;)Ljava/lang/Object;
  luontola#17 = Utf8               testpackage/StringBridges
  luontola#18 = Class              luontola#17            //  testpackage/StringBridges
  luontola#19 = Utf8               ()Ljava/lang/String;
  luontola#20 = NameAndType        luontola#10:luontola#19        //  get:()Ljava/lang/String;
  luontola#21 = InterfaceMethodref luontola#18.luontola#20        //  testpackage/StringBridges.get:()Ljava/lang/String;
  luontola#22 = Utf8               Code
  luontola#23 = Utf8               LineNumberTable
  luontola#24 = Utf8               SourceFile
{
  private testpackage.StringBridgeshelper();
    descriptor: ()V
    flags: ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial luontola#9                  // Method java/lang/Object."<init>":()V
         4: return

  public static java.lang.String get(testpackage.StringBridges);
    descriptor: (Ltestpackage/StringBridges;)Ljava/lang/String;
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=1, locals=1, args_size=1
         0: ldc           luontola#13                 // String default method
         2: areturn
      LineNumberTable:
        line 9: 0

  public static java.lang.String concrete(testpackage.StringBridges);
    descriptor: (Ltestpackage/StringBridges;)Ljava/lang/String;
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=1, locals=1, args_size=1
         0: ldc           luontola#15                 // String concrete
         2: areturn
      LineNumberTable:
        line 13: 0

  public static java.lang.Object get(testpackage.StringBridges);
    descriptor: (Ltestpackage/StringBridges;)Ljava/lang/Object;
    flags: ACC_PUBLIC, ACC_STATIC, ACC_BRIDGE, ACC_SYNTHETIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokeinterface luontola#21,  1           // InterfaceMethod testpackage/StringBridges.get:()Ljava/lang/String;
         6: areturn
      LineNumberTable:
        line 6: 0
}
@luontola
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luontola commented Aug 12, 2014

Um... What is this pull request about? Was it even meant to be a pull request?

@luontola
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luontola commented Aug 12, 2014

Oh, I got your email. So this is about default methods. I've now renamed it.

@luontola luontola changed the title package testpackage; Default methods Aug 12, 2014
@luontola
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luontola commented Aug 12, 2014

A feature like this requires thorough automated tests, which it currently does not have. Also the dependency to Scala is undesirable: it may cause conflicts with projects that use a different version of Scala, and it makes the program slower to start up (due to class loading overhead).

@Mart-Bogdan
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Mart-Bogdan commented Aug 13, 2014

It's seems Scala dependency is required only for retrolambda process itself, not at runtime.

I think this can cause some problems, if we implement standard interface with default methods.

@Arneball
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Arneball commented Aug 13, 2014

Dont sorry. I am porting the classes to java already

@luontola
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luontola commented Aug 25, 2014

Superseded by #30

@luontola luontola closed this Aug 25, 2014
@luontola luontola mentioned this pull request Sep 3, 2014
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3 participants

@Arneball @luontola @Mart-Bogdan