Problem with string concatonation.

[Energize]

So I have this method

public String encrypt(String message, int key) throws java.rmi.RemoteException {
		char[] charArray = message.toCharArray();  
        int[] numberArray = new int[message.length()];  
		int number;
		String data = "";

        for(int i = 0; i < message.length(); i++) { 
            numberArray[i] = charArray[i];
        }
		
        for (int i = 0; i < numberArray.length; i++) {
            if (numberArray[i] < 123 && numberArray[i] > 96) { 
				if (numberArray[i] < 120) { 
					numberArray[i] += 3;
				} else {
					numberArray[i] += 3 - 26;
				} 
			} else if (numberArray[i] < 91 && numberArray[i] > 64) { 
				if (numberArray[i] < 88) { 
					numberArray[i] += 3;
				} else {
					numberArray[i] += 3 - 26;
				}
			}
        }
		
        charArray = Integer.toString(key).toCharArray(); 
		
		for (int x = 0; x < numberArray.length; x++) {
			numberArray[x] -= charArray[x % charArray.length]; 
        }
		
        for (int x = 0; x < numberArray.length - 1; x += 2) { 
            number = numberArray[x];
            numberArray[x] = numberArray[x + 1];
            numberArray[x + 1] = number;
        }
		
		for(int x = 0; x < numberArray.length; x++) {
			[b]data.concat(Integer.toString(numberArray[x]));[/b]
		}
		
		return data;
	}

For some reason the line in bold doesn't seem to do anything, the string is returned empty, yet system.print prints out all the numbers correctly.

 

[redeye_uk]

dont you need to parse it into itself?

i.e

data = data.concat(Integer.toString(numberArray[x]));

 

[Energize]

Yeah that would explain it.