由于5.4%不是Double，因此您必须使用Scanner方法将String读取为输入，例如next或nextLine。但是要确保所读取的字符串是以％结尾的双精度字符串，可以使用hasNext(String pattern)方法。

if (input.hasNext("^[0-9]{1,}(.[0-9]*)?%$")) {
        String inputString = input.next();
        double rate = Double.parseDouble(inputString.substring(0,inputString.length() - 1));
        System.out.println("Your Annual rate " + rate + " is an error");
    }

   // Pattern explanation 
   ^ - Start of string
   [0-9]{1,} - ensure that at least one character is number
   [.[0-9]*]* - . can follow any number which can be followed by any number
   %$ - ensure that string must end with %

以上代码将确保仅传递以Double结尾的%个数字

由于您的输入不再是双精度型，因此不能再使用[global] workgroup = WORKGROUP realm = EXAMPLE.LOCAL dedicated keytab file = FILE:/etc/samba/samba.keytab kerberos method = dedicated keytab log file = /var/log/samba/log.%m security = ads [homes] browsable = no writable = yes [shared] path = /shared writable = yes browsable=yes write list = @admins ，您需要以字符串形式获取它，替换'％'，然后将其解析为双精度型。

input.nextDouble()

我会选择：

    public static void main(String[] args) {
     // TODO code application logic here
    Scanner input = new Scanner(System.in);
      System.out.println("Enter Annual Interest Rate");

      //user input is 5.4% for example

      //this is where the problem is because a double data type cannot contain the % 
      symbol:

      String userInput = input.nextLine(); // "5.4%"

      double percentage = Double.parseDouble(userInput.replace("%","")) / 100; // 0.54
      //You can now do calculations or anything you want with this value.

     //multiplying it with 100 to get it to % again
      System.out.println("Your Annual rate " + percentage*100 + "% is an error");
}