CODEWITHSUNDEEP
java
s_ofia
s_ofia

Reputation: 117

How to remove all non-numerical characters from a string input in java?

I am trying to create a basic calculator program and I want to remove all non-numerical characters from the string input. (I am a java newbie). This is my current code:

package calculator;
import javax.swing.JOptionPane;
public class sub {

    public static void main(String[] args) {

        //Text & Input Box #1
        String input = JOptionPane.showInputDialog(null,
                "Input the first number",
                "Subtraction",
                JOptionPane.QUESTION_MESSAGE);

        //Input Box #2
        String input1 = JOptionPane.showInputDialog(null,
                "Input the second number",
                "Subtraction",
                JOptionPane.QUESTION_MESSAGE);

        //Data Collection
        int data1 = Integer.parseInt(input);
        int data2 = Integer.parseInt(input1);

        //Data Sum
        int sum = data1 - data2;

        //Output
        JOptionPane.showMessageDialog(null,  sum, "The Answer",         
JOptionPane.INFORMATION_MESSAGE);

    }
}

Upvotes: 0

Views: 3344

Answers (4)

Yury
Yury

Reputation: 781

This handles null inputs (you need to include the Apache Commons Lang library, version 3.8 or higher, in your project):

import org.apache.commons.lang3.RegExUtils;
input = RegExUtils.removeAll(input, "-?[^\\d.]");

Library reference: https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/RegExUtils.html

Upvotes: 0

Ehsan
Ehsan

Reputation: 311

use a regular expression :

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MyClass {
    public static void main(String args[]) {
        String str = "asdjnk -#+-+1m245.g34.34";
        System.out.println("Input : " + str);
        double result = Double.parseDouble(extractNumber(str));
        System.out.println("Final result: " + result);    
    }

    public static String extractNumber(String input){

        //replace all characters except digits, +-.
        String regex = "[^-+0-9.]";
        input = input.replaceAll(regex, "");
        System.out.println("After remove non-digit characters: " + input);
        /* 
          number format: 
          [-]? : if there is 0 or 1 minus sign
          [0-9]+ : one or more digits
          [.]{1}[0-9]+ : . followed by one or more digits
        */
        regex = "[-]?[0-9]+([.]{1}[0-9]+)?";
        final Pattern pattern = Pattern.compile(regex);
        final Matcher matcher = pattern.matcher(input);
        if(matcher.find())
            return (matcher.group(0));
        else 
            return "error, no numbers exists!";

    }

}

result:

Input : asdjnk -#+-+1m245.g34.34
After remove non-digit characters: -+-+1245.34.34
Final result: 1245.34

Upvotes: 0

Arjun Anil
Arjun Anil

Reputation: 97

You can use this method to convert your string to only numericals: 

 public String getNumericString(String ourString)
  {

    StringBuilder neededCharacters = new StringBuilder();

    //Read throught the entire length of your input string
    for(int i = 0;i<ourString.length();i++)
    {
      //Get the current character
        char ch = ourString.charAt(i);

   //Check if the character is a numerical
        if (Character.isDigit(ch))
        {
         //if the character is a number then add it to our string 
        // builder
            neededCharacters.append(r.charAt(i));

        }
    }
    onlyNumericalString = needed.toString();
    return onlyNumericalString;
   }

You can ask me if you don't understand anything in the code.You should make small edits depending on your needs.

Upvotes: -1

tune5ths
tune5ths

Reputation: 723

You can use the String.replaceAll method with a regular expression like this:

input.replaceAll("-?[^\\d]", "");

Adding a . will allow decimal:

input.replaceAll("-?[^\\d.]", "");

Edited to support negative numbers.

Upvotes: 4

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