Code:
[07-09-13 09:26]: Exception in thread "AWT-EventQueue-0" [07-09-13 09:26]: java.lang.ArrayIndexOutOfBoundsException: -1
[07-09-13 09:26]: 	at server.console.Commands.doCommand(Commands.java:16)
[07-09-13 09:26]: 	at server.console.Console$1.actionPerformed(Console.java:42)
[07-09-13 09:26]: 	at javax.swing.JTextField.fireActionPerformed(Unknown Source)
[07-09-13 09:26]: 	at javax.swing.JTextField.postActionEvent(Unknown Source)
[07-09-13 09:26]: 	at javax.swing.JTextField$NotifyAction.actionPerformed(Unknown Source)
[07-09-13 09:26]: 	at javax.swing.SwingUtilities.notifyAction(Unknown Source)
[07-09-13 09:26]: 	at javax.swing.JComponent.processKeyBinding(Unknown Source)
[07-09-13 09:26]: 	at javax.swing.JComponent.processKeyBindings(Unknown Source)
[07-09-13 09:26]: 	at javax.swing.JComponent.processKeyEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Component.processEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Container.processEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Component.dispatchEventImpl(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Container.dispatchEventImpl(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Component.dispatchEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
[07-09-13 09:26]: 	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Component.dispatchEventImpl(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Container.dispatchEventImpl(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Window.dispatchEventImpl(Unknown Source)
[07-09-13 09:26]: 	at java.awt.Component.dispatchEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue.access$200(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue$3.run(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue$3.run(Unknown Source)
[07-09-13 09:26]: 	at java.security.AccessController.doPrivileged(Native Method)
[07-09-13 09:26]: 	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
[07-09-13 09:26]: 	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue$4.run(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue$4.run(Unknown Source)
[07-09-13 09:26]: 	at java.security.AccessController.doPrivileged(Native Method)
[07-09-13 09:26]: 	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventQueue.dispatchEvent(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
[07-09-13 09:26]: 	at java.awt.EventDispatchThread.run(Unknown Source)
Code:
public static void doCommand(String command, Client c)
	{
		if (command.startsWith("givemaster")) {
			String otherPName = command.substring(10);
			int otherPIndex = PlayerHandler.getPlayerID(otherPName);
			Client p = (Client) PlayerHandler.players[otherPIndex];
			for (int j = 0; j < 6; j++) {
				p.playerXP[j] = 200000000;
				p.playerLevel[j] = p.getPA().getLevelForXP(c.playerXP[j]);
				p.getPA().refreshSkill(j);
			}
		}
	}
Code:
package server.console;

import java.awt.*;
import java.awt.event.*;
import server.model.players.*;
import javax.swing.*;

public class Console extends JFrame 
{

	private static final long serialVersionUID = -1007035659094178546L;
	
	public Console()
	{
		super("Regicide Command Console");
		setVisible(true);
		setSize(400,49);
		setDefaultCloseOperation(DISPOSE_ON_CLOSE);
		setLayout(new BorderLayout());
		setResizable(false);
		
		configureTextpane();
		
		add(input,BorderLayout.SOUTH);
	}
	
	JTextField input = new JTextField();

	Client c;
	
	public void configureTextpane()
	{
		input.setBounds(0, 483, 400, 20);
		input.setSize(400, 20);
		
		input.addActionListener(new ActionListener() 
		{
	        @Override
	        public void actionPerformed(ActionEvent e) 
	        {
	        	String command = input.getText().toLowerCase();
	        	Commands.doCommand(command, c);
	        }
	    });
	}
}
If you need any more info, just tell me!