Java，字符串只接受字母和“if”语句

Question

This is the code I have in a setName() method which I want to only accept letters (not digits)

      playerName = ""; 
      if (playerName.isDigit)
      {System.out.println("Please enter letters only");
       } 

I am getting an error message which says "illegal parenthesised expression.

Answer 1

String type doesn't have isDigit property. Use the following code to check if your variable contains digits.

if (playerName.matches(".*\\d+.*")) {
    System.out.println("Please enter letters only");
} 

Answer 2

This code will work for you:

public static void setName ( String playerName ){
    if (playerName.matches(".*\\d.*") || playerName.isEmpty()) {
        System.out.println("Please enter letters only");
    } else {
        //Your code here
    }
}

Answer 3

You can use Lambda expression to check whether the input string contains only character or not. In your setName() method, do the following

playerName="abcd";             //Take playerName from user input or as method argument

if(playerName==null || playerName.equals("") || !playerName.chars().allMatch(Character::isLetter))
        System.out.println("Please enter letters only");

else{

    //Do your work if someone enters name containing only letters.

}

Answer 4

There's no isDigit method in String.class in Java, but there're lots of ways to do it.

Take a look: https://mkyong.com/java/java-how-to-check-if-a-string-is-numeric/