java - (Java RPG) if 语句中的对象构造

Question

我制作了 4 个类(法师、胭脂、战士和傻瓜)，它们扩展了“角色”类。其中每一个在各自的类别中都有自己特定的战斗方法。但是，由于在 if/else 语句中仅构造了这些对象中的一个，因此 java 无法将它们识别为存在。问题是我需要在 if/else 语句之外调用特定于类的方法。我尝试先将 4 个对象初始化为 null，然后构造/覆盖它们，但是当我调用该方法时，它仍然将它们称为 null。格式有点乱，但在这里:

编辑:感谢您的反馈!

public class Rpg {
    public static Warrior wplayer = null;
    public static Rouge rplayer = null;
    public static Mage mplayer = null;
    public static Fool fplayer = null;

    public static void main(String[] args){
        a2 = scan.nextInt();
        if (a2 == 1){
            Warrior wplayer = new Warrior();
        } else if (a2 == 2) {
            Rouge rplayer = new Rouge();
        } else if (a2 == 3) {
            Mage mplayer = new Mage();
        } else {
            Fool fplayer = new Fool();
            while (!notdone){
                System.out.println("1: Arena");
                System.out.println("2: Blacksmith");
                System.out.println("3: Shop");
                System.out.println("4: Leave town");
                System.out.println("5: Save and Quit");
                int choice = scan.nextInt();
                if (choice == 1 && wplayer != null){
                    wplayer.fightEnemy();
                } else if (choice == 1 && rplayer != null){
                    rplayer.fightEnemy();
                } else if (choice == 1 && mplayer != null){
                    mplayer.fightEnemy();
                } else {
                    fplayer.fightEnemy();
                }
            }
        }
    }   
}

Answer 1

这些变量的范围仅限于 if/else block 内。如果你想在外部访问它，你应该执行以下操作:

Character player = null;

if (a2==1){
    player = new Warrior();
} else if (a2==2){
    player = new Rouge();
} else if (a2==3){
    player = new Mage();
} else{
    player = new Fool();
}

// by now, player was instantiated by some concrete class and you can use it

如果每个角色都实现了自己的fightEnemy() 方法，那么您可以在这里利用多态性来自动选择正确的具体方法:

 ...
 if (choice==1){
        // java will figure out which "Character" this really is
        // then it will call the fightEnemy method for that specific "Character" type
        player.fightEnemy();
 }
 ...