Question

我正在做书店系统。用户必须选择是否添加，删除等。如果他选择添加，那么他将写出所有书籍属性，这些属性稍后将保存在项目数组中。项目数组是一个数组对象＆＃34; 这是我的代码

public class userChoices {

    Items[] items = new Items[200];
    AddItem add = new AddItem();
    Scanner s = new Scanner(System.in);

    public void add(){
        boolean invalidInput;
        int q = -1;
        do {        
            try {        
                invalidInput = false;
        System.out.println("How many book(s) you want to add?");
            q = s.nextInt();
            for(int i = 0; i < q; i++){
                add.getCode();
                add.getQuantity();
                add.getCostPrice();
                add.getDescription();
                add.getDiscount();
                add.getSellingPrice();
                add.getStatus();
                for(int r = 0; r < items.length; r++){
                    if(items[r] != null){
                        items[r] = new Items(add.getCode(), add.getDescription(), add.getQuantity(),
                                add.getCostPrice(), add.getSellingPrice(), add.getStatus(), add.getDiscount());
                        continue;
                    }
                }
            }

            } catch (InputMismatchException e) {
        System.out.println("Please enter a valid integer.");
                s.next();
        invalidInput = true;  // This is what will get the program to loop back
            }
    } while (invalidInput);
    }

this is my Items class
    public class Items {
    private int code, quantity;
    private String description;
    private double costPrice, sellingPrice;
    String status, discount;

    public Items(){
        this.code = 1111;
        this.quantity = 1;
        this.description = "Action";
        this.costPrice = 12.00;
        this.sellingPrice = 16.00;
        this.discount = "5%";
        this.status = "Unvailable";

    }

    public Items(int code, String description, int quantity,
            double costPrice, double sellingPrice, String status, String discount){
        this.code = code;
        this.description = description;
        this.quantity = quantity;
        this.costPrice = costPrice;
        this.sellingPrice = sellingPrice;
        this.status = status;
        this.discount = discount;
    }

    public void setCode(int code){
        this.code = code;
    }

    public void setQuantity(int quantity){
        this.quantity = quantity;
    }

    public void setDescription(String description){
        this.description = description;
    }

    public void setcostPrice(double costPrice){
        this.costPrice = costPrice;
    }

    public void setsellingPrice(double sellingPrice){
        this.sellingPrice = sellingPrice;
    }

    public void setStatus(String status){
        this.status = status;
    }

    public void setDiscount(String discount){
        this.discount = discount;
    }

    public int getCode(int code){
        this.code = code;
        return this.code;
    }

    public int getQuantity(int quantity){
        this.quantity = quantity;
        return this.quantity;
    }

    public String getDescription(String description){
        this.description = description;
        return this.description;
    }

    public double getcostPrice(double costPrice){
        this.costPrice = costPrice;
        return this.costPrice;
    }

    public double getsellingPrice(double sellingPrice){
        this.sellingPrice = sellingPrice;
        return this.sellingPrice;
    }

    public String getStatus(String status){
        this.status = status;
        return this.status;
    }

    public String getDiscount(String discount){
        this.discount = discount;
        return this.discount;
    }

    public String toString(){
        return ("code : " + this.code + "\nQuantity : " + this.quantity +
                "\nDescription : " + this.description + "\nCost price : " + this.costPrice
                + "\nSelling price : " + this.sellingPrice + "\nstatus : " + this.status
                + "\ndiscount : " + this.discount);
    }


}

当我在我添加后打印项目[0]时，它显示我＆＃34; null＆＃34;

Answer 1

除了其他人指出的if(items[r] != null){之外，我相信此代码中的continue语句是错误的：

for(int r = 0; r < items.length; r++){
    if(items[r] != null){
        items[r] = new Items(add.getCode(), add.getDescription(), add.getQuantity(),
                add.getCostPrice(), add.getSellingPrice(), add.getStatus(), add.getDiscount());
        continue;
    }
}

此声明将在下一次迭代中继续：

for(int r = 0; r < items.length; r++){

虽然在我看来你希望它继续下一次迭代

for(int i = 0; i < q; i++){

所以你应该使用break; 而不是continue;

吸气剂

public double getcostPrice(double costPrice){
    this.costPrice = costPrice;
    return this.costPrice;
}

这个“getter”本质上是一个setter，它返回你刚刚设置的值，而不是getter应该做的。

public double getcostPrice(){
    return this.costPrice;
}

这就是吸气剂应该起作用的方式。

Answer 2

你的错误在于这一行：

                    if(items[r] != null){

创建数组时，由于它是一个对象引用数组，因此它的所有元素都为null。因此，这种情况会导致它永远不会将项插入数组中。

无论如何你不应该有一个循环。您应该保留数组中下一个空位的索引，并使用它将该项放入数组中，然后递增（添加一个）它。

如何在对象数组中添加和打印？

2 个答案:

吸气剂