尝试更改变量的 Java 方法不起作用

Question

我目前正在编写一段游戏，其中敌人( bat )的生命值应该下降，但它不起作用。

class BatTest{
public static void main(String args[]) {
    String input = "";
    boolean exit = false;
    Bat bat1 = new Bat();
    Inventory MainInv = new Inventory();
    MainInv.smallknife = true;
    System.out.println("A bat has appeared!");
    System.out.println("Health: " + bat1.health + " Attack Strength: " + bat1.damage);
    do{
        System.out.println("Health: " + bat1.health + " Attack Strength: " + bat1.damage);
        System.out.print("What would you like to do: ");
        input = Keyboard.readString();
        if (input.equalsIgnoreCase("Attack")) {
            Abilities.smallknifeMA(bat1.health);
            System.out.println(bat1.health);
        }
        else if (input.equalsIgnoreCase("exit")) {
            exit = true;
        }
    }while(!exit);
}

}

//enemyH denotes the health of the enemy

class Abilities {
static double smallknifeMA(double enemyH) {
    enemyH = enemyH - 2.0;
    return enemyH;
}

}

class Inventory {
boolean smallknife;
boolean startlockerkey;

}

我真的不明白为什么smallknifeMA不降低变量bat1.health。

谢谢，极光

Answer 1

Java 不是按引用传递的。这个

Abilities.smallknifeMA(bat1.health);

需要更新bat1.health。比如，

bat1.health = Abilities.smallknifeMA(bat1.health);

或者，修改 smallknifeMA 以采用 Bat 参数并直接更新 health。比如，

static void smallknifeMA(Bat bat) {
    bat.health -= 2.0;
}

但是，将类成员设为 public 是一种不好的做法；您可能应该将此行为封装在 Bat 中。