Java Reflection Interactive

LiveScript.java

import java.util.*;
import java.lang.reflect.*;

public class LiveScript
{
	private LiveScript() throws UnsupportedOperationException
	{
		throw new UnsupportedOperationException();
	}

	public static void main(String[] args_unused)
	{
		Scanner in = new Scanner(System.in);
		HashMap<String, Object> objs = new HashMap<String, Object>();
		objs.put("null", null);
	CommandLoop:
		for(;;) try
		{
			System.out.print(">");
			String s = in.next();
			Scanner ln = new Scanner(in.nextLine());
			if(s.equals("Exit")) break;
			else if(s.equalsIgnoreCase("Help") || s.equals("?"))
			{
				System.out.println("Exit - exit this program");
				System.out.println("Set a b - sets a to the same as b");
				System.out.println("New class name constructor_args... - create a new object and assign it to name");
				System.out.println("Call name class method args... - invoke a method on name (or class if name is null)");
				System.out.println("Invoke a b class method args... - invoke a method on b (or class if name is null) and assign it to a");
				System.out.println("Use #name in argument lists to use name as its primitive type");
			}
			else if(s.equals("Set"))
			{
				String a = ln.next();
				if(!objs.containsKey(a))
				{
					System.out.println("No such object: "+a);
					continue CommandLoop;
				}
				else if(a.equals("null"))
				{
					System.out.println("Cannot assign to null");
					continue CommandLoop;
				}
				String b = ln.next();
				if(!objs.containsKey(b))
				{
					System.out.println("No such object: "+b);
					continue CommandLoop;
				}
				objs.put(a, a.getClass().cast(objs.get(b)));
			}
			else if(s.equals("New"))
			{
				String clazz = ln.next();
				Class c = Class.forName(clazz);
				String name = ln.next();
				if(name.equals("null"))
				{
					System.out.println("Cannot assign to null");
					continue CommandLoop;
				}
				String[] args = new String[0];
				if(ln.hasNext())
				{
					args = ParseArgs(ln.nextLine().substring(1));
				}
				Class[] types = ParseClasses(args, objs);
				Constructor ctor = c.getDeclaredConstructor(types);
				Object[] params = ParseParams(args, objs);
				objs.put(name, ctor.newInstance(params));
			}
			else if(s.equals("Call"))
			{
				String name = ln.next();
				if(!objs.containsKey(name))
				{
					System.out.println("No such object: "+name);
					continue CommandLoop;
				}
				Class c = Class.forName(ln.next());
				String method = ln.next();
				String[] args = new String[0];
				if(ln.hasNext())
				{
					args = ParseArgs(ln.nextLine().substring(1));
				}
				Class[] types = ParseClasses(args, objs);
				Method m = c.getDeclaredMethod(method, types);
				Object[] params = ParseParams(args, objs);
				Object o = m.invoke(objs.get(name), params);
				if(m.getReturnType().equals(Void.TYPE))
				{
					System.out.println("Returned");
				}
				else if(o == null)
				{
					System.out.println("Returned null reference to "+m.getReturnType());
				}
				else
				{
					System.out.println("Returned "+m.getReturnType()+": \""+o+"\"");
				}
			}
			else if(s.equals("Invoke"))
			{
				String a = ln.next();
				if(a.equals("null"))
				{
					System.out.println("Cannot assign to null");
					continue CommandLoop;
				}
				String name = ln.next();
				if(!objs.containsKey(name))
				{
					System.out.println("No such object: "+name);
					continue CommandLoop;
				}
				Class c = Class.forName(ln.next());
				String method = ln.next();
				String[] args = new String[0];
				if(ln.hasNext())
				{
					args = ParseArgs(ln.nextLine().substring(1));
				}
				Class[] types = ParseClasses(args, objs);
				Method m = c.getDeclaredMethod(method, types);
				if(m.getReturnType().equals(Void.TYPE))
				{
					System.out.println("Cannot assign void");
					continue CommandLoop;
				}
				Object[] params = ParseParams(args, objs);
				Object o = m.invoke(objs.get(name), params);
				objs.put(a, o);
			}
			else
			{
				System.out.println("Unkown Command, use Help or ? for help");
			}
		}
		catch(NoSuchObjectException e){}
		catch(NotConvertibleToPrimitiveException e){}
		catch(Throwable t){ t.printStackTrace(); }
	}
	static class NoSuchObjectException extends Exception {}
	static class NotConvertibleToPrimitiveException extends Exception {}
	static String[] ParseArgs(String line)
	{
		ArrayList<String> arr = new ArrayList<String>();
		String tok = "";
		boolean inq = false;
		for(char c : (line+' ').toCharArray())
		{
			if(c == '"')
			{
				if(inq)
				{
					arr.add(' '+tok);
					tok = "";
				}
				inq = !inq;
			}
			else if(c == ' ' && !inq)
			{
				if(!tok.equals(""))
				{
					arr.add(tok);
					tok = "";
				}
			}
			else
			{
				tok += c;
			}
		}
		return (String[])arr.toArray(new String[0]);
	}
	static HashMap<Class, Class> primitives = new HashMap<Class, Class>();
	static
	{
		primitives.put(Boolean.class, Boolean.TYPE);
		primitives.put(Byte.class, Byte.TYPE);
		primitives.put(Short.class, Short.TYPE);
		primitives.put(Character.class, Character.TYPE);
		primitives.put(Integer.class, Integer.TYPE);
		primitives.put(Long.class, Long.TYPE);
		primitives.put(Float.class, Float.TYPE);
		primitives.put(Double.class, Double.TYPE);
	}
	static Class[] ParseClasses(String[] args, HashMap<String, Object> objs) throws NoSuchObjectException, NotConvertibleToPrimitiveException
	{
		Class[] types = new Class[args.length];
		for(int i = 0; i < args.length; ++i)
		{
			if(args[i].charAt(0) == ' ')
			{
				types[i] = String.class;
			}
			else if(args[i].charAt(0) == '#')
			{
				String name = args[i].substring(1);
				if(!objs.containsKey(name))
				{
					System.out.println("No such object: "+args[i]);
					throw new NoSuchObjectException();
				}
				else if(!primitives.containsKey(objs.get(name).getClass()))
				{
					System.out.println("Not convertible to primitive: "+name);
					throw new NotConvertibleToPrimitiveException();
				}
				types[i] = primitives.get(objs.get(name).getClass());
				args[i] = name;
			}
			else if(!objs.containsKey(args[i]))
			{
				System.out.println("No such object: "+args[i]);
				throw new NoSuchObjectException();
			}
			else
			{
				types[i] = objs.get(args[i]).getClass();
			}
		}
		return types;
	}
	static Object[] ParseParams(String[] args, HashMap<String, Object> objs)
	{
		Object[] params = new Object[args.length];
		for(int i = 0; i < args.length; ++i)
		{
			if(args[i].charAt(0) == ' ')
			{
				params[i] = args[i].substring(1);
			}
			else
			{
				params[i] = objs.get(args[i]);
			}
		}
		return params;
	}
}