如何检查字符串是否包含数值

Question

I want to know how to do I check my sub string if it is a numerical value or if it is just words.

For example, if my substring d=150.63

I have done some research and I've found Character.is Digit() , but it is not working. Below is the code I have made so far.

import java.util.*;
import java.io.*;

public class Prac34 {

    private Scanner x;

    public void openFile(){
      try{
        x=new Scanner(new File("sales.txt"));
      }
      catch (Exception e){
        System.out.println("could not find file");    
      }
    }

    public void readFile(){
      //int count=0;
      double total=0;
      while(x.hasNext()){

        String a=x.nextLine();
        int v=a.length();

        int b=a.indexOf(':');
        String c= a.substring(0,(b+1));

        String d=a.substring((b+1),v);
        double e= Double.parseDouble(d);

        if (Character.isDigit(d)) {
          total=total+e;
        }


        System.out.println(c);
        System.out.println(d);
}
}

    public void closeFile(){
      x.close();
    }
}

Answer 1

You could just try to parse the string:

try {
    double e = Double.parseDouble(d);
    total += e;
} catch (NumberFormatException ignore) {
    // Not a number, skipping
}

Answer 2

Using a regex (regular expression):

String text="25.54";
     if(text.replace(".","").matches("[0-9]+")){ //or you can use also "\\d+"
         System.out.println("digit");
     }else{
      System.out.println("no digit");
     }

     System.out.println(text);

Also:

where ( ? ) means none or one time

where (*) means none or more times

where ( + ) means one or more times

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