如果参数未满足，则重新启动while循环

因此，此程序可以运行，但它会运行，但我希望它是白痴证明！要做到这一点，我需要一些帮助。如果用户输入了一个数字或者什么都没有，我不希望它进入下一行！如果参数未满足，则重新启动while循环

如果我按下输入而没有写任何东西，它仍会进入下一行，并且变量navn在末尾完全变空。如果我写一个数字，它会做同样的事情。如果回答不符合提示，我将如何返回并再次尝试相同的while循环。非常感谢你:)

import java.util.Scanner; 

class Metoder { 

    public static void main(String[] args) { 
     String bosted; //Variable 
     String navn; //Variable 

     Scanner in = new Scanner(System.in); 

     System.out.println("Skriv inn navn: "); //What shows up when you first start the program 

     while (!in.hasNext("[A-Za-z]+")) { //Only allow letters A-Z 
      in.next(); 
      System.out.println("Tall horer ikke hjemme i navn, prøv igjen!"); //Prints, "numbers dont belong in names, try again" if what the user entered is a number 

     } 
     System.out.println("Takk!"); //Says thank you if the user has entered letters 

     navn = in.nextLine(); //Proceeds to next line 

     System.out.println("Skriv inn bosted: "); //Next line, where the user is supposed to enter where he/she lives 
     while (!in.hasNext("[A-Za-z]+")) { //Excactly the same loop as above 
      in.next(); 
      System.out.println("Tall hører ikke hjemme i stedsnavn, prøv igjen!"); 
     } 
     System.out.println("Takk!"); 

     bosted = in.nextLine(); 

     System.out.println("Hei, " + navn + "! Du er fra " + bosted + "."); //Prints out what the user has entered previously in a full sentence. 

    } 
}

来源

2016-08-30 Bjørn Olav Jalborg

。 – Berger

是的，谢谢！ –

将所有内容放在while循环中只有当变量包含任何值时才退出while循环 –

请使用此代码：当您使用几次相同的代码，可以考虑把它专用的方法中

public static void main(String[] args) { 
    String bosted=""; //Variable 
    String navn=""; //Variable 

    Scanner in = new Scanner(System.in); 

    System.out.println("Skriv inn navn: "); //What shows up when you first start the program 

    while(in.hasNext()) { //Only allow letters A-Z 
     navn = in.nextLine(); 
     if(!navn.isEmpty() && navn.matches("[A-Za-z]+")){ 
      System.out.println("Takk!"); //Says thank you if the user has entered letters 
      in.next(); 
      break; 
     } 
     else{ 
      System.out.println("Tall horer ikke hjemme i navn, prøv igjen!"); //Prints, "numbers dont belong in names, try again" if what the user entered is a number 
      in.next(); 
      System.out.println("Skriv inn navn: "); 
      continue; 
     } 

    } 

    System.out.println("Skriv inn bosted: "); 
    while(in.hasNext()) { //Only allow letters A-Z 
     bosted = in.nextLine(); 
     if(!bosted.isEmpty() && bosted.matches("[A-Za-z]+")){ 
     System.out.println("Takk!"); //Says thank you if the user has entered letters 
     break; 
     } 
     else{ 
      System.out.println("Tall horer ikke hjemme i navn, prøv igjen!"); //Prints, "numbers dont belong in names, try again" if what the user entered is a number 
      in.next(); 
      System.out.println("Skriv inn bosted: "); 
      continue; 
     } 


} 
    System.out.println("Hei, " + navn + "! Du er fra " + bosted + "."); //Prints out what the user has entered previously in a full sentence. 
}

来源

2016-08-30 14:37:58

可以使用continue关键字基本上重新启动循环。

while(!in.hasNext("[A-Za-z]+")) { 
    try { 
     String s = in.nextLine(); 
     if(s.isEmpty() || s.matches("^-?\\d+$")){ 
      throw new Exception("empty string or number detected"); 
     } 
    } catch (Exception e){ 
     continue; 
    } 
}

在这种if条件，我们检查，如果输入的字符串是空的，或者是一个整数，我们可以抛出一个异常，这将导致直到条件失败while循环继续要求输入（即通过了我们测试）。

来源

2016-08-30 14:02:53 px06

如果参数未满足，则重新启动while循环

回答

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