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我确定对此有一个简单的答案，但是当我将余额设置为负数时，我希望系统打印一个错误，目前，它只是将负数打印到控制台，有人可以帮助我吗至于为什么会发生这种情况。任何答复表示赞赏。 

package Assignment1;

public class Customer
{
    private String name;
    private String address;
    private int balance;

    public Customer(String nameParam, String addressParam, int balanceParam)
    {   
        name = nameParam;  
        address = addressParam;
        balance = balanceParam;
    }

    public void setName(String nameParam)
    {
        name = nameParam;
    }

    public String getName()
    {
        return name;
    }

    public void setAddress(String addressParam)
    {
        address = addressParam;
    }

    public String getAddress()
    {
        return address;
    }

    //I want the system to print an error should the balanceParam be less than 0
    public void setBalance(int balanceParam)
    {
        if (balanceParam >= 0)
        {
            balance = balanceParam;
        }
        else
        {
            System.out.println("Error: Invalid balance");
        }

    }


    public int getBalance()
    {
        return balance;
    }



    public static void main(String[] args) 
    {

        Customer customer1 = new Customer("Tom", "High Street", 100);
        Customer customer2 = new Customer("Mary", "Low Street", 110);

            //The balance for customer3 is set to a negative number
        Customer customer3 = new Customer("John", "Middle Street", -10);

        System.out.print(customer1.getName() + "\t");
        System.out.print(customer1.getAddress()+ "\t");
        System.out.println(customer1.getBalance());

        System.out.print(customer2.getName()+ "\t");
        System.out.print(customer2.getAddress()+ "\t");
        System.out.println(customer2.getBalance());

        System.out.print(customer3.getName()+ "\t");
        System.out.print(customer3.getAddress()+ "\t");
        System.out.println(customer3.getBalance());

    }

}
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2 回答 2

1

请注意，检查发生在您的setBalance()方法中，但您从不调用此方法。特别是，您的构造函数balance直接设置字段而无需类似的检查 解决此问题的一种方法（同时减少重复）是setBalance()从构造函数调用（和其他设置器）。

于 2013-09-07T21:54:23.933 回答
1

您永远不会调用setBalence打印错误的方法。

要在构造Customer对象后立即打印错误，请更改构造函数以使用类字段的 setter 方法

public Customer(String nameParam, String addressParam, int balanceParam)
{   
    setName(nameParam);  
    setAddress(addressParam);
    setBalance(balanceParam);
}

此外，您可能希望通过抛出异常来防止构建此类对象或将负余额设置为现有对象：

public void setBalance(int balanceParam) {
    if (balanceParam < 0) {
        throw new IllegalArgumentException("Error: Invalid balance");
    }
    balance = balanceParam;
}
于 2013-09-07T21:57:20.027 回答