更新方法GameWorld不起作用

Question

我正在通过本教程学习libGDX：http://www.kilobolt.com/day-4-gameworld-and-gamerenderer-and-the-orthographic-camera.html

当我尝试运行DesktopLauncher时遇到问题，经过多次研究，没有人遇到同样的问题：

Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: java.lang.NoSuchMethodError: com.kilobolt.gameworld.GameWorld.update(F)V
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:131)
Caused by: java.lang.NoSuchMethodError: com.kilobolt.gameworld.GameWorld.update(F)V
at com.kilobolt.screens.GameScreen.render(GameScreen.java:19)
at com.badlogic.gdx.Game.render(Game.java:46)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:223)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:124)

  Process finished with exit code 0

这是我的GameScreen类：

package com.kilobolt.screens;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Screen;
import com.badlogic.gdx.graphics.GL20;
import com.kilobolt.gameworld.GameRenderer;
import com.kilobolt.gameworld.GameWorld;

public class GameScreen implements Screen {

private GameWorld world;
private GameRenderer renderer;

public GameScreen() {
    Gdx.app.log("GameScreen", "Attached");
    world = new GameWorld();
    renderer = new GameRenderer();
}

@Override
public void render(float delta) {
    world.update(delta);
    renderer.render();
}

@Override
public void resize(int width, int height) {

}

@Override
public void show() {
    Gdx.app.log("GameScreen", "show called");
}

@Override
public void hide() {
    Gdx.app.log("GameScreen", "hide called");
}

@Override
public void pause() {
    Gdx.app.log("GameScreen", "pause called");
}

@Override
public void resume() {
    Gdx.app.log("GameScreen", "resume called");
}

@Override
public void dispose() {
    // Leave blank
}

}

我的GameWorld课程：

    package com.kilobolt.gameworld;
    import com.badlogic.gdx.Gdx;

public class GameWorld {

public void update(float delta) {
    Gdx.app.log("GameWorld", "update");
}
}

我的GameRenderer课程：

package com.kilobolt.gameworld;

import com.badlogic.gdx.Gdx;

public class GameRenderer {

public void render() {
    Gdx.app.log("GameRenderer", "render");
}
}

感谢您的回答。