source: galactic-heroes/HumanShip.java

import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;

public class HumanShip extends Ship {
    private boolean upPressed;
    private boolean downPressed;
    private boolean leftPressed;
    private boolean rightPressed;
    private long timeDownPressed;
    private long timeUpPressed;
    private long timeLeftPressed;
    private long timeRightPressed;
    private int startUpPressed;
    private int startDownPressed;
    private int startLeftPressed;
    private int startRightPressed;
    
    public HumanShip(final int newX, final int newY, final int newSpeed, final int newMaxHitpoints, final int newDamage, final int newShotSpeed, final int newShotInterval, final BufferedImage newPic, final BufferedImage newShotPic) {
        super(newX, newY, newSpeed, newMaxHitpoints, 0, newDamage, newShotSpeed, newShotInterval, 0, -25, newPic, newShotPic);
        this.upPressed = false;
        this.downPressed = false;
        this.leftPressed = false;
        this.rightPressed = false;
        this.timeDownPressed = 0L;
        this.timeUpPressed = 0L;
        this.timeLeftPressed = 0L;
        this.timeRightPressed = 0L;
    }
    
    public void handleEvent(final KeyEvent e) {
        switch (e.getKeyCode()) {
            case 38: {
                if (!this.upPressed) {
                    this.timeUpPressed = System.currentTimeMillis();
                    this.startUpPressed = this.getY();
                    this.upPressed = true;
                    break;
                }
                break;
            }
            case 40: {
                if (!this.downPressed) {
                    this.timeDownPressed = System.currentTimeMillis();
                    this.startDownPressed = this.getY();
                    this.downPressed = true;
                    break;
                }
                break;
            }
            case 37: {
                if (!this.leftPressed) {
                    this.timeLeftPressed = System.currentTimeMillis();
                    this.startLeftPressed = this.getX();
                    this.leftPressed = true;
                    break;
                }
                break;
            }
            case 39: {
                if (!this.rightPressed) {
                    this.timeRightPressed = System.currentTimeMillis();
                    this.startRightPressed = this.getX();
                    this.rightPressed = true;
                    break;
                }
                break;
            }
        }
    }
    
    public void draw(final Graphics g) {
        int xChange = 0;
        int yChange = 0;
        if (this.upPressed) {
            yChange -= (int)((System.currentTimeMillis() - this.timeUpPressed) * this.getSpeed() / 1000L);
        }
        if (this.downPressed) {
            yChange += (int)((System.currentTimeMillis() - this.timeDownPressed) * this.getSpeed() / 1000L);
        }
        if (this.leftPressed) {
            xChange -= (int)((System.currentTimeMillis() - this.timeLeftPressed) * this.getSpeed() / 1000L);
        }
        if (this.rightPressed) {
            xChange += (int)((System.currentTimeMillis() - this.timeRightPressed) * this.getSpeed() / 1000L);
        }
        if ((!this.downPressed || this.timeUpPressed < this.timeDownPressed) && this.upPressed) {
            this.setY(this.startUpPressed + yChange);
        }
        else if (this.downPressed) {
            this.setY(this.startDownPressed + yChange);
        }
        if (this.upPressed && this.downPressed) {
            this.timeUpPressed = System.currentTimeMillis();
            this.timeDownPressed = System.currentTimeMillis();
            this.startUpPressed = this.getY();
            this.startDownPressed = this.getY();
        }
        if ((!this.rightPressed || this.timeLeftPressed < this.timeRightPressed) && this.leftPressed) {
            this.setX(this.startLeftPressed + xChange);
        }
        else if (this.rightPressed) {
            this.setX(this.startRightPressed + xChange);
        }
        if (this.getX() < this.getPic().getWidth() / 2) {
            this.setX(this.getPic().getWidth() / 2);
        }
        if (this.getX() > 800 - this.getPic().getWidth() / 2) {
            this.setX(800 - this.getPic().getWidth() / 2);
        }
        if (this.getY() < 0 + this.getPic().getHeight() / 2) {
            this.setY(0 + this.getPic().getHeight() / 2);
        }
        if (this.getY() > 600 - this.getPic().getHeight() / 2) {
            this.setY(600 - this.getPic().getHeight() / 2);
        }
        if (this.leftPressed && this.rightPressed) {
            this.timeLeftPressed = System.currentTimeMillis();
            this.timeRightPressed = System.currentTimeMillis();
            this.startLeftPressed = this.getX();
            this.startRightPressed = this.getX();
        }
        super.draw(g);
    }
    
    public void reset() {
        super.reset();
        this.upPressed = false;
        this.downPressed = false;
        this.leftPressed = false;
        this.rightPressed = false;
        this.timeDownPressed = 0L;
        this.timeUpPressed = 0L;
        this.timeLeftPressed = 0L;
        this.timeRightPressed = 0L;
        this.startUpPressed = 0;
        this.startDownPressed = 0;
        this.startLeftPressed = 0;
        this.startRightPressed = 0;
    }
    
    public void setUpPressed(final boolean pressed) {
        this.upPressed = pressed;
    }
    
    public void setDownPressed(final boolean pressed) {
        this.downPressed = pressed;
    }
    
    public void setLeftPressed(final boolean pressed) {
        this.leftPressed = pressed;
    }
    
    public void setRightPressed(final boolean pressed) {
        this.rightPressed = pressed;
    }
}