Java - how to convert letters in a string to a number?

Question

I\'m quite new to Java so I am wondering how do you convert a letter in a string to a number e.g. hello world would output as 8 5 12 12 15 23 15 18 12 4

Answer 1

Usa a Map with the key being the character and an value being the integers. This is not an efficient way - the map should be a static member of the class.

import java.util.HashMap;
import java.util.Map;


public class JavaApplication1 
{
    public static void main(String[] args) 
    {
        final Map<Character, Integer> map;
        final String str = "hello world";

        map = new HashMap<>();  
        // or map = new HashMap<Character, Integer> if you are using something before Java 7.
        map.put('a', 1);
        map.put('b', 2);
        map.put('c', 3);
        map.put('d', 4);
        map.put('e', 5);
        map.put('f', 6);
        map.put('g', 7);
        map.put('h', 8);
        map.put('i', 9);
        map.put('j', 10);
        map.put('k', 11);
        map.put('l', 12);
        map.put('m', 13);
        map.put('n', 14);
        map.put('o', 15);
        map.put('p', 16);
        map.put('q', 17);
        map.put('r', 18);
        map.put('s', 19);
        map.put('t', 20);
        map.put('u', 21);
        map.put('v', 22);
        map.put('w', 23);
        map.put('x', 24);
        map.put('y', 25);
        map.put('z', 26);

        for(final char c : str.toCharArray())
        {
            final Integer val;

            val = map.get(c);

            if(val == null)
            {   
                // some sort of error
            }
            else
            {
                System.out.print(val + " ");
            }
        }

        System.out.println();
    }
}

Answer 2

If you need you can use below tested code to convert string into number if your string contains only numbers and alphabets.

 public static Long getNumericReferenceNumber(String str) {

        String result = "";

        for (int i = 0; i < str.length(); i++) {

            char ch = str.charAt(i);

            if (Character.isLetter(ch)) {
                char initialCharacter = Character.isUpperCase(ch) ? 'A' : 'a';
                result = result.concat(String.valueOf((ch - initialCharacter + 1)));
            } else result = result + ch;
        }

        return Long.parseLong(result);
    }