Java 字符串乘以 2 个整数

Question

我尝试根据 2 个字符串相乘来搜索多个线程。然而，似乎我找到的大多数链接都不适用，或者我无法很好地解释它们。

是否可以告诉我当前代码有什么问题？

public static void main(String[] args) {

    String sample = value1();
    String sample2 = value2();
            //========== Test if users placed any characters within the boxes =========\\
            try {
                Integer.parseInt(sample);
            } catch (NumberFormatException e) {
                System.out.println("System detects that you are using characters");
                return;
            }
            try {
                Integer.parseInt(sample2);
            } catch (NumberFormatException e) {
                System.out.println("System detects that you are using characters");
                return;
            }
     Integer.parseInt(sample); 
     Integer.parseInt(sample2);
    System.out.println("The total multiplication that you have inserted is "+sample * sample2+ ".");
}

public static String value1() { //obtain first user input. 

    String sample = JOptionPane.showInputDialog(null, "Insert Value", "Enter amount ", JOptionPane.QUESTION_MESSAGE);
    if (sample.isEmpty()) {

        JOptionPane.showMessageDialog(null, "Error!", "No Value Detected", JOptionPane.ERROR_MESSAGE);
        sample = value1();


    }
    return sample;

}

public static String value2() { //obtain second user input. 

    String sample2 = JOptionPane.showInputDialog(null, "Insert Value", "Enter amount ", JOptionPane.QUESTION_MESSAGE);
    if (sample2.isEmpty()) {

        JOptionPane.showMessageDialog(null, "Error!", "No Value Detected", JOptionPane.ERROR_MESSAGE);
        sample2 = value2();


    }
    return sample2;

}    

}

我的最终输出应该乘以以下数字

System.out.println("您插入的总乘法为 "+sample * sample2+ ".");

Answer 1

不能将字符串相乘。您可以将数字相乘，听起来这就是您想要做的。事实上，您已经将字符串解析为整数 - 然后忽略结果。您只需要更改此:

 Integer.parseInt(sample); 
 Integer.parseInt(sample2);
 System.out.println("The total multiplication that you have inserted is "+sample * sample2+ ".");

至:

 int value1 = Integer.parseInt(sample); 
 int value2 = Integer.parseInt(sample2);
 System.out.println("The total multiplication that you have inserted is "
     + (value1 * value2) + ".");