java - For 循环未在方法中启动

Question

我对编码非常陌生，所以我正在练习一些简单的东西，遇到了一个我已经尝试解决大约 2 个小时的问题，但我不知道它出了什么问题。

问题是，当我调用 crate.fillCrate(); 或 crate.emptyCrate(); 时，控制台中不会出现任何内容，而当我调用 crate.crateInfo(); 控制台中出现以下内容:

一箱漂亮的喜力啤酒
它包含 24 个插槽
插槽:已满。
插槽:为空。

我想这意味着我的 for 循环没有启动，但我不知道为什么......

我的主课:

public class Main {

    public static void main(String[] args) {
        Crate crate = new Crate(24, "Heineken");
    }
}

我的 crate 类:

public class Crate {
    private int crateSize;
    private Bottle[] bottles = new Bottle[crateSize];
    public String brand = null;

    public Crate(int crateSize, String brand) {
        this.crateSize = crateSize;
        this.brand = brand;
    }

    public void fillCrate(){
        for(int i = 0; i < bottles.length; i++) {
            if(bottles[i] == null && !bottles[i].getSpotInfo()) {
                bottles[i] = new Bottle(true);
                System.out.println("Spot " + (i+1) + " is filled.");
            } else {
                System.out.println("Spot " + (i+1) + " was already full");
            }
        }
    }

    public void emptyCrate() {
        for(int i = 0; i < bottles.length; i++) {
            if(bottles[i] != null && bottles[i].getSpotInfo()) {
                bottles[i].makeSpotEmpty();
                System.out.println("Spot " + (i+1) + " is empty."); 
            } else {
                System.out.println("Spot " + (i+1) + " was already empty");
            }
        }
    }

    public void crateInfo() {
        System.out.println("A nice crate of " + brand);
        System.out.println("It contains " + crateSize + " slots");
        System.out.print("slots: ");
        for(int i = 0; i < bottles.length; i++) {
            if(bottles[i] != null && bottles[i].getSpotInfo()) {
                System.out.print((i+1));
            }
        }
        System.out.println(" are filled.");
        System.out.print("slots: ");
        for(int c = 0; c < bottles.length; c++) {
            if(bottles[c] != null && !bottles[c].getSpotInfo()) {
                System.out.print((c+1));
            }
        }
        System.out.println(" are empty.");
    }
}

还有我的 Bottle 类:

public class Bottle {
    private boolean occupiesSpot = false;

    public Bottle(boolean occupiesSpot) {
        this.occupiesSpot = occupiesSpot;
    }

    public void makeSpotEmpty() {
        occupiesSpot = false;       
    }

    public boolean getSpotInfo() {
        return occupiesSpot;
    }
}

Answer 1

    private int crateSize;
    private Bottle[] bottles = new Bottle[crateSize];

瓶子的大小为 0，因为 crateSize 尚未初始化，您应该这样做

    public Crate(int crateSize, String brand) {
        this.crateSize = crateSize;
        this.brand = brand;
        this.bottles = new Bottle[crateSize];
    }

还有

if (bottles[i] == null && bottles[i].getSpotInfo())

如果瓶子为空，则此行将导致 NullPointerException，因为您无法对空对象调用方法 (getSpotInfo)。也感谢@Turing85 指出了这一点。