使用Java检查用户输入是否为空

Question

我环顾四周，找不到解决方案。我的代码应该从用户处获得输入，并在输入为空时停止。代码最初很简单，但现在我认为我已经过于复杂了，所以很抱歉。

Scanner read = new Scanner(System.in); 
System.out.println("Input words, enter blank to stop"); 
boolean working = true; 
do { 
    if(working == false) 
    { 
     break; 
    } 

    String a = read.next(); 

    if (a.equals("")) { 
     working = false; 
     System.out.println("no data");  
    } else { 
     Container.addWord(a); 
    } 
} while (working == true); 

谢谢。

Answer 1

下一个（）改为nextLine（）：

Scanner read = new Scanner(System.in); 
    System.out.println("Input words, enter blank to stop"); 
    boolean working = true; 
    do { 
     if (working == false) { 
      break; 
     } 
     String a = read.nextLine(); 
     if (a.isEmpty()) { 
      working = false; 
      System.out.println("no data"); 

     } else { 

      Container.addWord(a); 
     } 

    } while (working == true); 

Answer 2

yourString.isEmpty() || yourString.equals("") 

Answer 3

可以简化整个事情：

Scanner read = new Scanner(System.in); 
    System.out.println("Input words, enter blank to stop"); 
    boolean working = true; 
    do { 
     String keyEntered = read.nextLine(); 

     if (keyEntered.isEmpty()) { 
     working = false; 
     System.out.println("No data"); 
     } else { 
     System.out.println("You entered: " + keyEntered); 
     } 
    } while (working); 

Answer 4

您是否尝试过使用String#trim().isEmpty()

它也将考虑像" "这样的字符串为空。

do { 
    String a = read.next(); 

    if (a.trim().isEmpty()) { 
     working = false; 
     System.out.println("no data");  
    } else { 
     Container.addWord(a); 
    } 
} while (working); 

Answer 5

我觉得你的代码可以用下面的替换：

Scanner read = new Scanner(System.in); 
System.out.println("Input words, enter blank to stop"); 
while(true) {  
    if (!read.hasNext()) { 
     System.out.println("no data"); 
     break; 
    } 
    String a = read.next(); 
    Container.addWord(a); 
} 

我也去掉了working变量，并用break声明取代了它。

如果更改read.next()到read.nextLine()一定要同时更新read.hasNext()到read.hasNextLine()。

Answer 6

这是更优雅一点的第一个“如果”声明是没有用的，因为它的工作通假，你不会在while循环进入下一次版本

public static void main(String...args){ 
    Scanner read = new Scanner(System.in); 
    String line = null; 
    System.out.println("Enter text:"); 
    while(!(line=read.nextLine()).equals("")){ 
     System.out.println("Your text:"+line); 
     System.out.println("Enter text or press enter to exit:"); 
    } 

    System.out.println("Bye bye !!!"); 
}