String.concat() doesn't do concatenation

Question

I am trying to concatenate a String with an int and char including spaces, but not getting any concatenation. What is the reason?

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(" ");

Answer 1

concat does not alter the invoking strings, but returns a new one.

You may assign each resulting String to your result like this.-

messages = messages.concat(String.valueOf(random));
messages = messages.concat(" ");
messages = messages.concat(String.valueOf(ch));
messages = messages.concat(" ");

Or just use the overloaded operator +

messages = String.valueOf(random) + " " + String.valueOf(ch) + " ";