尝试抓取扫描仪 [英] try catch for Scanner

问题描述

我正在使用扫描器来获取用户输入。如果用户输入一个名称，我将其添加到 ArrayList 中。如果用户没有输入名称，那么我想要抛出一个异常，但是我想继续循环得到答案。

I am using Scanner to get user input. If the user inputs a name, I add that to the ArrayList. If the user does not enter a name then I want to throw an exception, but I want to continue the loop that gets the answer.

for(int i = 0; i < totalLanes; i++){
    runArr.add(this.addRacer());
}

public static String addRacer() throws NullPointerException{
    System.out.print("Enter a name for a racer: ");//Method uses try catch to catch a    NullPointerException.   
    Scanner sc = new Scanner(System.in);
    String rName = null;
    try {            
        if(!sc.nextLine().isEmpty()){
            rName = sc.nextLine();
        }else{
            throw new NullPointerException("name cannot be blank");
        }
    }

    catch (NullPointerException e) {
        System.out.println(e.toString());
        System.out.print("Enter a name for a racer: ");
        addRacer();
    }
    return rName;
}

• 为什么会无限次递归？ >
  
• 从用户那里获取输入的最佳方式是什么？
  确保输入有效数据？



提前感谢

推荐答案

问题是您读取输入两次。
我的意思是你的代码中有两个调用 sc.nextLine（）方法。
尝试这样做：

The problem is that you read input twice. I mean you have two calls of sc.nextLine() method in your code. Try this instead:

String rName = sc.nextLine();
try {
    if(rName.isEmpty()){
        throw new NullPointerException("Name cannot be blank.");
    }
}

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