java - 单击 Enter 时如何解决扫描仪错误

Question

Scanner scan = new Scanner (System.in);
mainMenu = scan.nextLine().charAt(0);

每次我点击输入时，它都会“爆炸”并说:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
    at java.lang.String.charAt(Unknown Source)
    at tESTedit.main(tESTedit.java:50). 

我该如何解决这个问题？

Answer 1

只需检查字符串是否有内容

Scanner scan = new Scanner (System.in);
String input = null;

if (scan.hasNextLine() && !(input = scan.nextLine()).isEmpty()) {
  char mainMenu = input.charAt(0);
  // do something else
} else {
  System.err.println("Nothing was entered");
}

System.out.println("Hello " + input);