[jug.bg] Building Valhalla and using primitives as generic arguments

Project Valhalla will probably be part of Java 10 (expected 2018). Among other things it allows using primitives as generic arguments.

Building Valhalla

On a linux/unix/osx box we start with:

hg clone http://hg.openjdk.java.net/valhalla/valhalla
cd valhalla
bash get_source.sh  #this one takes some time
bash configure
make clean images # this one takes some cpu

Box<int>

We can have a class like this:

public class Program  {
	public static void main(String[] args) {
		// this one still doesn't work, List not updated to List
//		List l = new ArrayList();
//		l.add(5);
//		System.out.println(l.get(0));
 
		Box b = new Box(6);
		System.out.println(b.get());
	}
}
 
class Box {
    private final T t;
    public Box(T t) { this.t = t; }
    public T get() { return t; }
}

javap

Running javap gives

$ javap -c Program.class gives:
[openjdk@localhost bin]$ ./javap -c Program.class 
Compiled from "Program.java"
public class Program {
  public Program();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."":()V
       4: return
 
  public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class "Box${0=I}"
       3: dup
       4: bipush        6
       6: invokespecial #3                  // Method "Box${0=I}"."":(I)V
       9: astore_1
      10: getstatic     #4                  // Field java/lang/System.out:Ljava/io/PrintStream;
      13: aload_1
      14: invokevirtual #5                  // Method "Box${0=I}".get:()I
      17: invokevirtual #6                  // Method java/io/PrintStream.println:(I)V
      20: return
}

Running our pretty simple app gives:

[openjdk@localhost bin]$ ./java Program
Specializing Box${0=I}; searching for Box.class (not found)
Specializing Box${0=I}; searching for Box.class (found)
6
[openjdk@localhost bin]$

Notes: List is still not parameterized with because ... issues.

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