在游戲開發中，通常會使用一個堆棧（stack）來存儲游戲中的狀態，比如玩家位置、游戲進度等。當玩家需要返回上一步時，可以簡單地從堆棧中取出上一個狀態并恢復到該狀態。

以下是一個簡單的示例代碼，演示如何在游戲開發中使用堆棧來實現返回上一步的功能：

import java.util.Stack;

public class Game {
    private Stack<String> gameStateStack;

    public Game() {
        gameStateStack = new Stack<>();
    }

    public void saveGameState(String state) {
        gameStateStack.push(state);
    }

    public String loadPreviousState() {
        if (!gameStateStack.isEmpty()) {
            return gameStateStack.pop();
        } else {
            return "No previous state available";
        }
    }

    public static void main(String[] args) {
        Game game = new Game();

        // Simulate game progress
        game.saveGameState("Level 1");
        game.saveGameState("Level 2");
        game.saveGameState("Level 3");

        // Player wants to go back to previous state
        String previousState = game.loadPreviousState();
        System.out.println("Previous state: " + previousState);

        // Player wants to go back to previous state again
        previousState = game.loadPreviousState();
        System.out.println("Previous state: " + previousState);

        // Player wants to go back to previous state again
        previousState = game.loadPreviousState();
        System.out.println("Previous state: " + previousState);

        // Player wants to go back to previous state again, but there is no more previous state available
        previousState = game.loadPreviousState();
        System.out.println("Previous state: " + previousState);
    }
}

在上面的示例中，我們創建了一個Game類來模擬游戲的狀態變化，并使用堆棧gameStateStack來保存游戲狀態。通過調用saveGameState方法可以保存當前游戲狀態，而調用loadPreviousState方法則可以返回上一個游戲狀態。

當我們運行上面的代碼時，可以看到輸出結果如下：

Previous state: Level 3
Previous state: Level 2
Previous state: Level 1
Previous state: No previous state available

可以看到，通過堆棧的方式，我們可以方便地實現返回上一步的功能，在游戲開發中可以幫助玩家在需要時回退到之前的游戲狀態。