classbuilder

public class JavaCompiler {
    String name;
    ArrayList<?> data = new ArrayList();
    int constantPoolEnd;

    public static JavaCompiler getCompiler (String s, Package p) {
        JavaCompiler returnCompiler;
        try {
            new SecurityManager.checkCreateClassLoader();
            returnCompiler = new JavaCompiler(s, p);
        } catch (SecurityException se) {
            returnCompiler = null;
        } finally {
            return returnCompiler;
        }
    }

    JavaCompiler (String s, Package p) {
        String packageName = p.getName().replace(".", "/").concat("/").concat(s);
        //Add "magic"
        data.add(0xCAFEBABE);
        //Add the version number, minor number first, then major number
        data.add((short) 0); data.add((short) 61);
        //Add the constant pool
        data.add((short) 4);
        data.add((byte) 7); data.add((short) 1);
        data.add((byte) 1); data.add((short) packageName.length()); data.add(packageName);
        data.add((byte) 7); data.add((short) 3);
        data.add((byte) 1); data.add((short) 16); data.add("java/lang/Object");
        //Mark the end of the constant pool
        constantPoolEnd = 14;
        //Add access flags
        data.add(JavaCompiler.getDefaultAccessFlags.bytes()[0]); data.add(JavaCompiler.getDefaultAccessFlags.bytes()[1]);
        //Add this class and super class
        data.add((short) 0); data.add((short) 2);
        //Add interfaces
        data.add((short) 0);
        //Add fields
        data.add((short) 0);
        //Add methods
        data.add((short) 0);
        //Add attributes
        data.add((short) 0);
        this.name = name;
    }

    public void setAccessFlags (AccessFlags af) {
    }

    public Class<?> build () {
        ArrayList<byte> classData = new ArrayList();
        for (Object o : data) {
            if (o instanceof byte) {
                classData.add(o);
            } else if (o instanceof short) {
                classData.add(java.nio.ByteBuffer.allocate(2).putShort(o).array());
            } else if (o instanceof int) {
                classData.add(java.nio.ByteBuffer.allocate(4).putInt(o).array());
            } else if (o instanceof long) {
                classData.add(java.nio.ByteBuffer.allocate(8).putLong(o).array());
            } else if (o instanceof String) {
                classData.add(java.nio.ByteBuffer.allocate(o.length()).putInt(o).array());
            } else {
                throw new IllegalStateException("Class object is not a number or string.");
            }
        }
        return ClassLoader.geSystemClassLoader().defineClass(name, classData, 0, classData.length);
    }