mobile keypad

DecodeTheCode.java

package test.decodethecode;
import java.util.HashMap;
import java.util.regex.Pattern;
import java.util.regex.Matcher;


public class DecodeTheCode {
    HashMap<String, String> encodings = new HashMap<String, String>();
    
    public void hashInit() {
        //create hash table
        encodings.put("2", "a");encodings.put("22", "b");encodings.put("222", "c");
        encodings.put("3", "d");encodings.put("33", "e");encodings.put("333", "f");
        encodings.put("4", "g");encodings.put("44", "h");encodings.put("444", "i");
        encodings.put("5", "j");encodings.put("55", "k");encodings.put("555", "l");
        encodings.put("6", "m");encodings.put("66", "n");encodings.put("666", "o");
        encodings.put("7", "p");encodings.put("77", "q");encodings.put("777", "r");
        encodings.put("7777", "s");encodings.put("8", "t");encodings.put("88", "u");
        encodings.put("888", "v");encodings.put("8888", "8");encodings.put("9", "w");
        encodings.put("99", "x");encodings.put("999", "y");encodings.put("9999", "z");
        encodings.put("0", " ");       
    }
    
    public String decodeCode(String encodedString)    {
        StringBuilder resultInEachStep = new StringBuilder();
        hashInit();
        
        //pattern checking for a valid input
        boolean flag = Pattern.matches("(((\\d)\\3*)(#\\3)?)+", encodedString);
        if(!flag)  
            return null; //string invalid
        
        Pattern p = Pattern.compile("(\\d)\\1*");
        Matcher m = p.matcher(encodedString);
        while(m.find()){
          resultInEachStep.append(encodings.get(m.group(0)));
        }
        
        return  resultInEachStep.toString();
    }
}