正确使用构造函数来更改 int 值？

Question

我有 2 个 class。 1. Main 和 2. Gun.

枪支：

public class Gun {
    private int ammoAmount = 15;
    public int getAmmoAmount() { //I believe this allows me to see the value of ammoAmount and use it in Main class.
        return ammoAmount; // Returns the value of ammoAmount to getAmmoAmount?
    }
    public Gun(int ammoUsage) { //this is the constructor right?
        ammoAmount = ammoAmount - ammoUsage; //Method that makes ammoAmount decrease by ammoUsage.
    }
    public void newAmmoAmount() {
        System.out.println("You have " + ammoAmount + " bullet(s) left."); // output of how much bullet is left.
    }
}

主要：

import java.util.Random;
public class Main {

    public static void main(String[] args) {

        Random rand = new Random();
        Gun fire1 = new Gun(0); // I need this to create an objective?
        fire1.newAmmoAmount(); // I need this for code below?
        int clip = fire1.getAmmoAmount(); // I need this to set clip for while loop?
        do { //starts loop
        int x = 5; //max # random can go to.
        int y = rand.nextInt(x); //Makes random integer from 0 to 5 for variable y.
        Gun fire = new Gun(y); //This is the objective that uses the constructor?
        System.out.println("You shot " + y + " bullet(s)."); //Print's out shots from random value y.
        fire.newAmmoAmount(); //uses method in Gun class?
        } while( clip > 0); //loops method till clip is less than 0.
    }
}

我尝试运行这个程序，但它一直在循环，永远不会结束。 ammoAmount 的值未保存在 Gun class 中。我该怎么做才能从不同的 class?

更改 int 值

我最近也有一个问题。我试过按照他所说的那样使用构造函数。

How do I call a class into a class from main? and keep the output values?

但是如您所见，我不是很成功。这只是我试图达到的更大概念的一个更小概念。所以基本上，我做的构造函数对吗？解决这个问题的方法是什么？

我在源代码中添加了一些注释，以向您展示我可能遇到的其他问题以及我是否也做对了。

Answer 1

您的 "Gun" 对象是不可变的 - 没有任何东西可以改变该对象的状态。这样的类型有很多用法，但不太可能是你想要的。

听起来您想要 "Gun" 的实例到 "fire"，因此 "Gun" 实例中重命名项目符号的数量会减少。绝对创建新的 "Gun" 对象不会改变第一个中的项目符号数。

public class Gun {
    ...
    public fire(int ammoUsage) {
        ammoAmount = ammoAmount - ammoUsage; // TODO: add check for less than 0 
    }
}

通过这次更新 class 你可以 fire 直到没有子弹：

   int maxBulletsPerRound = 5; 
   Gun gun = new Gun(0); // fully loaded
   int clip;
   do {
    int numberOfBullets = rand.nextInt(maxBulletsPerRound); 
    gun.fire(numberOfBullets);
    System.out.println("You shot " + numberOfBullets + " bullet(s)."); 
    gun.newAmmoAmount(); //uses method in Gun class?
    clip = gun.getAmmoAmount(); // check how many bullets left
  } while( clip > 0);

请注意，最好只使用 while(gun.getAmmoAmount() > 0)。

Answer 2

好吧，让我先解释一下你做了什么，而不是我假设你想要的。

public static void main(String[] args) {
    //create random class instance
    Random rand = new Random();
    //initialize a Gun object with 0 bullets used (so 15 left)
    Gun fire1 = new Gun(0); 
    //the following line just prints "You have 15 bullet(s) left."
    fire1.newAmmoAmount();
    //following line puts 15 in the clip integer
    int clip = fire1.getAmmoAmount(); 
    do { //starts loop
        int x = 5; //max # random can go to.
        int y = rand.nextInt(x); //Makes random integer from 0 to 5 for variable y.
        //you create a new Gun object with y bullets used (you probably did not want that)
        Gun fire = new Gun(y); //This is the objective that uses the constructor?
        System.out.println("You shot " + y + " bullet(s)."); //Print's out shots from random value y.
        //the following line just prints that you have 15-y bullets left
        fire.newAmmoAmount(); //uses method in Gun class?
        //while continues forever, clip is never updated
    } while( clip > 0); //loops method till clip is less than 0.
}

好的，我知道我打字太慢了，@Alexei 的答案可能就是您要找的。

重点是你创建了一个对象的2个实例，这两个实例不能互相影响，它们是两个完全独立的东西，你可以把它看成两个人（Bas 和 Alexei）例如，他们都是 class Human（我猜 :P），但是如果你调用 Bas.setAge(25)，Alexei 的年龄保持不变。

希望对您有所帮助。

正确使用构造函数来更改 int 值？

properly using constructors to change int value?

java

constructor

integer