How should I implement Jumping/gravity/falling in this 2d Java Game
<p>So Here's my <code>Player</code> class (The object I would like to jump on spacebar), I just don't know where to begin, are there any good resources I can read on the internet that relates to me? Any help is great, thank-you.</p>

<pre><code>package com.zetcode;
import java.awt.Color;
import java.awt.Graphics;

public class Player extends Creature {

    private boolean jumping = false;
    private Creature creature;

    public Player(Handler handler, float x, float y) {
        super(handler, x, y, Creature.PLAYER_WIDTH, Creature.PLAYER_HEIGHT);

        bounds.x = 16;
        bounds.y = 31;
        bounds.width = 40;
        bounds.height = 58;
    }

    @Override
    public void tick() {
        getInput();
        move();
        handler.getGameCamera().centerOnEntity(this);
    }

    private void getInput(){
        xMove = 0;
        yMove = 3;
        gravity = 2;

        if(handler.getKeyManager().jump)
            yMove = -speed;
        if(handler.getKeyManager().down)
            yMove = speed;
        if(handler.getKeyManager().left)
            xMove = -speed;
        if(handler.getKeyManager().right)
            xMove = speed;
    }

    @Override
    public void render(Graphics g) {
        g.drawImage(Assets.player, (int) (x -     handler.getGameCamera().getxOffset()), (int) (y -   handler.getGameCamera().getyOffset()), width, height, null);
    }
}
</code></pre>

<p>And here is my <code>KeyManager</code> class:</p>

<pre><code>package com.zetcode;

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

public class KeyManager implements KeyListener{

    private boolean[] keys;
    public boolean up, down, left, right, jump;

    public KeyManager(){
        keys = new boolean[256];
    }

    public void tick(){
        down = keys[KeyEvent.VK_S];
        left = keys[KeyEvent.VK_A];
        right = keys[KeyEvent.VK_D];
        jump = keys[KeyEvent.VK_SPACE];
    }

    @Override
    public void keyPressed(KeyEvent e) {
        keys[e.getKeyCode()] = true;
        System.out.println("A Key was pressed");
    }

    @Override
    public void keyReleased(KeyEvent e) {
        keys[e.getKeyCode()] = false;
    }

    @Override
    public void keyTyped(KeyEvent e) {

    }
}
</code></pre>

<p>I have been struggling to implement a way for my character to jump, currently the player moves up the Y axis on spacebar press but I can hold the key down and jump endlessly.</p>

<p>I'll add my <code>Creature</code> class which has my collision detection: </p>

<pre><code>package com.zetcode;

public abstract class Creature extends Entity {

    public static final int DEFAULT_HEALTH = 10;
    public static final float DEFAULT_SPEED = 3.0f;
    public static final int DEFAULT_CREATURE_WIDTH = 64,
            DEFAULT_CREATURE_HEIGHT = 64;
    public static final int PLAYER_HEIGHT = 90, PLAYER_WIDTH = 64;

    protected int health;
    protected float speed;
    protected float xMove, yMove;
    protected float gravity;

    public boolean falling = true;
    private boolean jumping = false;

    public Creature(Handler handler, float x, float y, int width, int height) {
        super(handler, x, y, width, height);
        health = DEFAULT_HEALTH;
        speed = DEFAULT_SPEED;
        xMove = 0;
        yMove = 0;
        gravity = 0;
    }

    //collision detection

    public void move(){
        moveX();
        moveY();
    }

    public void moveX(){
        if(xMove &gt; 0){//move right
            int tx = (int) (x + xMove + bounds.x + bounds.width) / Tile.TILE_WIDTH;

            if(!collisionWithTile(tx, (int) (y + bounds.y) / Tile.TILE_HEIGHT) &amp;&amp; //check top right corner of hitbox
                    !collisionWithTile(tx, (int) (y + bounds.y + bounds.height) / Tile.TILE_HEIGHT)){ //check bottom right corner of hitbox
                x += xMove;
            }else{
                x = tx * Tile.TILE_WIDTH - bounds.x - bounds.width - 1;
            }

        }else if(xMove &lt; 0){//move left
            int tx = (int) (x + xMove + bounds.x) / Tile.TILE_WIDTH;

            if(!collisionWithTile(tx, (int) (y + bounds.y) / Tile.TILE_HEIGHT) &amp;&amp; //check top left corner of hitbox
                    !collisionWithTile(tx, (int) (y + bounds.y + bounds.height) / Tile.TILE_HEIGHT)){ //check bottom left corner of hitbox
                x += xMove;
            }else{
                x = tx * Tile.TILE_WIDTH + Tile.TILE_WIDTH - bounds.x;
            }
        }
    }

    public void moveY(){
        if(yMove &lt; 0){//up
            int ty = (int) (y+ yMove + bounds.y) / Tile.TILE_HEIGHT;

            if(!collisionWithTile((int) (x + bounds.x) / Tile.TILE_WIDTH, ty) &amp;&amp;
                    !collisionWithTile((int) (x + bounds.x + bounds.width) / Tile.TILE_WIDTH,ty)){
                y += yMove;
            }else{
                y = ty * Tile.TILE_HEIGHT + Tile.TILE_HEIGHT - bounds.y;
            }

        }else if(yMove &gt; 0){//down
            int ty = (int) (y+ yMove + bounds.y + bounds.getHeight()) /      Tile.TILE_HEIGHT;

            if(!collisionWithTile((int) (x + bounds.x) / Tile.TILE_WIDTH,ty) &amp;&amp;
                    !collisionWithTile((int) (x + bounds.x + bounds.width) /   Tile.TILE_WIDTH,ty)){
                y += yMove;
            }else{
                y = ty * Tile.TILE_HEIGHT - bounds.y - bounds.height -1;
            }
        }
    }

    protected boolean collisionWithTile(int x, int y){
        return handler.getWorld().getTile(x, y).isSolid();
    }

    //getters and setters

    public float getxMove() {
        return xMove;
    }

    public void setxMove(float xMove) {
        this.xMove = xMove;
    }

    public float getyMove() {
        return yMove;
    }

    public void setyMove(float yMove) {
        this.yMove = yMove;
    }

    public int getHealth() {
        return health;
    }

    public void setHealth(int health) {
        this.health = health;
    }

    public float getSpeed() {
        return speed;
    }

    public void setSpeed(float speed) {
        this.speed = speed;
    }
}
</code></pre>