CustomStringToInt.java

import java.util.HashMap;

public class CustomStringToInt {
	
	/**
	 * Initialize the HashMap with the decimal numbers.
	 *
	 * @return     The initialized HashMap.
	 */
	private static HashMap<Character, Integer> initCharToIntMap() {
		HashMap<Character, Integer> chars = new HashMap<Character, Integer>();
		
		chars.put('0', 0);		chars.put('1', 1);
		chars.put('2', 2);		chars.put('3', 3);
		chars.put('4', 4);		chars.put('5', 5);
		chars.put('6', 6);		chars.put('7', 7);
		chars.put('8', 8);		chars.put('9', 9);
		
		return chars;
	}
	
	/**
	 * @var chars The HashMap that was created in initCharToIntMap()
	 */
	private static HashMap<Character, Integer> chars = initCharToIntMap();
	
	/**
	 * Gets the int for this character. It is outsourced from the convert()
	 * method to catch java.lang.NullPointerException|s that might occur when
	 * requesting not mapped characters (e.g. in "12b3", b will return -1).
	 * Although removeNonDigits() should have thrown them out, I guess it's kind
	 * of good habit to catch this thing.
	 *
	 * @param      key   The "requested" character.
	 * @return     The int for character or -1 if character is not mapped.
	 */
	private static int getIntForChar(char key) {
		try {
			return chars.get(key);
		} catch (NullPointerException e) {
			return -1;
		}
	}
	
	/**
	 * Remove all non-digit characters from the string set. 
	 *
	 * @param      in    The raw string.
	 * @return     A string with digits only.
	 */
	private static String removeNonDigits(String in) {
		return in.replaceAll("[^\\d.]", "");
	}

	/**
	 * The callable Method which does the magic.
	 *
	 * @param      in    The String that comes in.
	 * @return     The unsigned integer that will come back.
	 */
	public static int convert(String in) {
		in = removeNonDigits(in);
		System.out.println(in);
		
		int result = 0;
		int exp = in.length() - 1;
		
		for(int i = 0; i < in.length(); i++) {
			int num = getIntForChar(in.charAt(i));
			if(num < 0) {
				continue;
			}
				
			result += num * Math.pow(10, exp);
			exp -= 1;
		}
		
		return result;
	}
	
}