import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class playerOne here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class playerOne extends Mover
{
 /**
     * Constructor 
     */
    public playerOne()
    {
        this.velocity = 4;
    }    
/**
     * Act - do whatever the playerOne wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        checkKeys();
    } 

    /**
     * Check if a key is pressed
     */
    public void checkKeys()
    {
        // move the player right
        if(Greenfoot.isKeyDown("right"))
        {
            setLocation(getX()+velocity, getY());
        }
        //move the player left
        if(Greenfoot.isKeyDown("left"))
        {
            setLocation(getX()-velocity, getY());
        }
        //move the player up
        if(Greenfoot.isKeyDown("up"))
        {
            setLocation(getX(), getY()-velocity);
        }
        //move the player down
        if(Greenfoot.isKeyDown("down"))
        {
            setLocation(getX(), getY()+velocity);
        }
    }
}
____________________________________________________

Player Two

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class playerOne here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class PlayerTwo extends Mover
{
 /**
     * Constructor 
     */
    public PlayerTwo()
    {
        this.velocity = 4;
    }    
/**
     * Act - do whatever the playerOne wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        checkKeys();
    } 

    /**
     * Check if a key is pressed
     */
    public void checkKeys()
    {
        // move the player right
        if(Greenfoot.isKeyDown("d"))
        {
            setLocation(getX()+velocity, getY());
        }
        //move the player left
        if(Greenfoot.isKeyDown("a"))
        {
            setLocation(getX()-velocity, getY());
        }
        //move the player up
        if(Greenfoot.isKeyDown("w"))
        {
            setLocation(getX(), getY()-velocity);
        }
        //move the player down
        if(Greenfoot.isKeyDown("s"))
        {
            setLocation(getX(), getY()+velocity);
        }
    }
}