java - 输出打印一个小于最终 int 的值

Question

当总人数小于 0 时，如何让该程序输出“无效数据”而不是“总人数”？

另外，为什么当我在“输入人数”时输入格式问题时，它会打印“总人数”，然后让我再次输入“离开人数”。我怎样才能让它提示我输入“数字输入”直到有效？

 final int MAX_PEOPLE = 65; 
  final int MIN_PEOPLE = 0;
  int totalPeople = 0;  

  while (totalPeople <= MAX_PEOPLE) {             
     try  {  
        int numLeaving = Integer.parseInt(JOptionPane.showInputDialog("number leaving:"));
        int numEntering = Integer.parseInt(JOptionPane.showInputDialog("number entering:"));      
        if (numLeaving < MIN_PEOPLE || numEntering < MIN_PEOPLE) { 
           JOptionPane.showMessageDialog(null,"Invalid data");                                                                    
        }          
        else {                         
           totalPeople = (totalPeople + numEntering) - numLeaving;
        }
     }
     catch (NumberFormatException e) {
        JOptionPane.showMessageDialog(null,"Enter numbers only");
     }  
     if (totalPeople > MAX_PEOPLE) {
        JOptionPane.showMessageDialog(null,"Capacity exceeded");
     } 
     else {
        JOptionPane.showMessageDialog(null,"Total people");              
     }
  }

Answer 1

我发现您的程序有 2 个问题

1. 如果在“号码输入”或“号码离开”中输入无效输入，则应分别提示返回“号码输入”或“号码离开”。

2. 它应该输出“无效数据”是变量 totalPeople <0.

您可以通过创建 while 来解决第一个问题循环 numLeaving和numEntering并检查无效输入，直到收到正确的输入，如下所示:

对于numLeaving :

    int numLeaving = -1;
    while(numLeaving < MIN_PEOPLE){
        try{
            numLeaving = Integer.parseInt(JOptionPane.showInputDialog("number leaving:"));
            if(numLeaving < MIN_PEOPLE){
                JOptionPane.showMessageDialog(null,"Invalid data"); 
            }
        }catch(NumberFormatException ex){
            JOptionPane.showMessageDialog(null,"Enter numbers only");
        }
    }

对于numEntering :

    int numEntering = -1;
    while(numEntering < MIN_PEOPLE){
        try{
            numEntering = Integer.parseInt(JOptionPane.showInputDialog("number entering:"));
            if(numEntering < MIN_PEOPLE){
                JOptionPane.showMessageDialog(null,"Invalid data"); 
            }
        }catch(NumberFormatException ex){
            JOptionPane.showMessageDialog(null,"Enter numbers only");
        }
    }

现在上面的代码消除了检查 (numLeaving < MIN_PEOPLE || numEntering < MIN_PEOPLE) 的要求因为它已得到照顾。所以你可以简单地计算totalPeople并检查它是否小于 0 并执行适当的操作，如下所示:

    totalPeople = (totalPeople + numEntering) - numLeaving;
    if (totalPeople < MIN_PEOPLE) { 
       JOptionPane.showMessageDialog(null,"Invalid data"); 
       totalPeople = 0;
       continue;                                                                   
    }     

我觉得这些建议可以解决您的问题。