String Concatenation in android

String Concatenation in android

I am trying to concatenate the string with integer and char including
spaces but not getting any concatentation, Whats the reason?Please help
private String messages;
Random r = new Random();
int random = r.nextInt(1000);
char ch='s';
messages.concat(String.valueOf(random));
messages.concat(" ");
messages.concat(String.valueOf(ch));
messages.concat(" ");