Java support (no, seriously)

Commands:

javac Foo.java
javap - c Foo

Example code:

import java.util.ArrayList;

class Foo {

  void iterateList() {
    ArrayList<Integer> list = new ArrayList<Integer>();
    list.add(1);
    list.add(2);
    list.add(3);

    for (int i : list) {
      System.out.println(i);
    }
  }

  void iterateArray() {
    int[] array = {1, 2, 3};

    for (int i : array) {
      System.out.println(i);
    }
  }

}

Example output:

Compiled from "Foo.java"
class Foo extends java.lang.Object{
Foo();
  Code:
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."<init>":()V
   4:   return

void iterateList();
  Code:
   0:   new #2; //class java/util/ArrayList
   3:   dup
   4:   invokespecial   #3; //Method java/util/ArrayList."<init>":()V
   7:   astore_1
   8:   aload_1
   9:   iconst_1
   10:  invokestatic    #4; //Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
   13:  invokevirtual   #5; //Method java/util/ArrayList.add:(Ljava/lang/Object;)Z
   16:  pop
   17:  aload_1
   18:  iconst_2
   19:  invokestatic    #4; //Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
   22:  invokevirtual   #5; //Method java/util/ArrayList.add:(Ljava/lang/Object;)Z
   25:  pop
   26:  aload_1
   27:  iconst_3
   28:  invokestatic    #4; //Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
   31:  invokevirtual   #5; //Method java/util/ArrayList.add:(Ljava/lang/Object;)Z
   34:  pop
   35:  aload_1
   36:  invokevirtual   #6; //Method java/util/ArrayList.iterator:()Ljava/util/Iterator;
   39:  astore_2
   40:  aload_2
   41:  invokeinterface #7,  1; //InterfaceMethod java/util/Iterator.hasNext:()Z
   46:  ifeq    72
   49:  aload_2
   50:  invokeinterface #8,  1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
   55:  checkcast   #9; //class java/lang/Integer
   58:  invokevirtual   #10; //Method java/lang/Integer.intValue:()I
   61:  istore_3
   62:  getstatic   #11; //Field java/lang/System.out:Ljava/io/PrintStream;
   65:  iload_3
   66:  invokevirtual   #12; //Method java/io/PrintStream.println:(I)V
   69:  goto    40
   72:  return

void iterateArray();
  Code:
   0:   iconst_3
   1:   newarray int
   3:   dup
   4:   iconst_0
   5:   iconst_1
   6:   iastore
   7:   dup
   8:   iconst_1
   9:   iconst_2
   10:  iastore
   11:  dup
   12:  iconst_2
   13:  iconst_3
   14:  iastore
   15:  astore_1
   16:  aload_1
   17:  astore_2
   18:  aload_2
   19:  arraylength
   20:  istore_3
   21:  iconst_0
   22:  istore  4
   24:  iload   4
   26:  iload_3
   27:  if_icmpge   50
   30:  aload_2
   31:  iload   4
   33:  iaload
   34:  istore  5
   36:  getstatic   #11; //Field java/lang/System.out:Ljava/io/PrintStream;
   39:  iload   5
   41:  invokevirtual   #12; //Method java/io/PrintStream.println:(I)V
   44:  iinc    4, 1
   47:  goto    24
   50:  return

}

[jkeam]

I just wanted to tag on and say that I’m working on a bunch of projects to show the disassembled code for languages that I find interesting.

So far I’ve done: http://erlangbytes.io/ http://javabytes.io/ http://rubybytes.io/

With plans to do elixir and python next. Feedback is always welcome 😃

[mattgodbolt]

@joewalnes we actually have a PR pending to implement this… after only seven and a bit years…