$$Lambda$ class files

CFR version

CFR 0.151

Compiler

unknown, java 8?

Description

When decompiling .jar file (decompiled with dex2jar, also tried enjarify, same output), i get multiple $$Lambda$ .class files along with some .class files, but in code clogged with unreadable code. But when i ran in procyon, it decompiled without those $$Lambda$ .class files, and at least got all in one place, in java, even if not perfect. So it must have to do with Java 8 lambda expressions, or whatever it is.

Example

this is file content

ls
 InstanceSettings.java      
Service.java                      
 'SettingsActivity$$Lambda$14.java'  
'SettingsActivity$$Lambda$5.java'  
 SettingsActivity.java
'Provider$$Lambda$1.java'  
'SettingsActivity$$Lambda$10.java'  
'SettingsActivity$$Lambda$1.java'  
 'SettingsActivity$$Lambda$6.java'   
Settings.java
'Provider$$Lambda$2.java' 
 'SettingsActivity$$Lambda$11.java'  
'SettingsActivity$$Lambda$2.java'   
'SettingsActivity$$Lambda$7.java'
 Provider.java            
 'SettingsActivity$$Lambda$12.java' 
 'SettingsActivity$$Lambda$3.java'  
 'SettingsActivity$$Lambda$8.java'
 RemoteViewsFactory.java   
'SettingsActivity$$Lambda$13.java'  
'SettingsActivity$$Lambda$4.java'   
'SettingsActivity$$Lambda$9.java'

and just a small fraction of code, to see how it looks in code

final class RandomVersePopup$$Lambda$1
implements CompoundButton.OnCheckedChangeListener {
    private final RadioButton arg$1;

    private RandomVersePopup$$Lambda$1(RadioButton radioButton) {
        this.arg$1 = radioButton;
    }

    private static CompoundButton.OnCheckedChangeListener get$Lambda(RadioButton radioButton) {
        return new RandomVersePopup$$Lambda$1(radioButton);
    }

    public static CompoundButton.OnCheckedChangeListener lambdaFactory$(RadioButton radioButton) {
        return new RandomVersePopup$$Lambda$1(radioButton);
    }

    @LambdaForm.Hidden
    public void onCheckedChanged(CompoundButton compoundButton, boolean bl) {
        RandomVersePopup.access$lambda$0(this.arg$1, compoundButton, bl);
    }

[leibnitz27]

I don’t like the idea of undoing this sort of thing automatically (especially not something as complex as this), because I want to actually see the java represented by the bytecode.

That being said, I can imagine given code like the above, it’s really useful to see what’s really going on - so - there’s an EXPLICIT argument sugarretrolambda, (hey, it’ll probably never get used, but it’s a nice toy to have).

I’m not going to enable this automatically, so I may add something in the future to warn it might be appropriate.

(also the code’s a bit of a mess 😉 )

Normal

    private void confirmAndDeleteSelectedItems() {
        AlertDialog.Builder builder = new AlertDialog.Builder((Context)this);
        builder.setTitle(2131297197);
        int n = this.getSelectedItemsCount();
        if (n == 1) {
            builder.setMessage((CharSequence)this.getString(2131296860, new Object[]{((Map)this.itemsData.get(this.getSelectedItemIndex())).get("name")}));
        } else {
            builder.setMessage((CharSequence)this.getString(2131296861, new Object[]{n}));
        }
        builder.setNegativeButton(2131296302, null);
        builder.setPositiveButton(2131296306, Profiles$$Lambda$6.lambdaFactory$((Profiles)this));
        builder.show();
    }

With --sugarretrolambda true

    private void confirmAndDeleteSelectedItems() {
        AlertDialog.Builder builder = new AlertDialog.Builder((Context)this);
        builder.setTitle(2131297197);
        int n = this.getSelectedItemsCount();
        if (n == 1) {
            builder.setMessage((CharSequence)this.getString(2131296860, new Object[]{this.itemsData.get(this.getSelectedItemIndex()).get(KEY_NAME)}));
        } else {
            builder.setMessage((CharSequence)this.getString(2131296861, new Object[]{n}));
        }
        builder.setNegativeButton(2131296302, null);
        builder.setPositiveButton(2131296306, (DialogInterface dialogInterface, int n) -> {
            this.deleteSelectedItems();
        });
        builder.show();
    }

[Lanchon]

then again, decompilation is mostly done to understand the code, not to recompile it. and enabled helps understanding…

maybe youll find that sensible defaults are different for analyzing than for roundtripping. a general “roundtrip” option could disable all stuff like this while otherwise defaulting to analysis mode.