help to understand the ? mark in this code

[carolain79@hotmail.com]

can somebody help me to understand this line of code
s = args.length == 1 ? args[0] : "";

in the following program :

/* <assign> => <id> = <expr> ;
* <id> => a | b | c
* <expr> => 0 | ... | 9 | (<assign>)
*/



public class Main {

public static void main(String[] args) {

s = args.length == 1 ? args[0] : "";

if (assign() && i == s.length()) {
System.out.println("The string \"" + s + "\" is in the language.");
}
else {
System.out.println("The string \"" + s + "\" is not in the language.");
}
}

private static boolean assign() {

if (id()) {
if (i < s.length() && s.charAt(i) == '=') {
++i;
if (expr()) {
if (i < s.length() && s.charAt(i) == ';') {
++i;
return true;
}
}
}
}

return false;
}

private static boolean expr() {

if (i < s.length() && s.charAt(i) >= '0' && s.charAt(i) <= '9') {
++i;
return true;
}
else if (i < s.length() && s.charAt(i) == '(') {
++i;
if (assign()) {
if (i < s.length() && s.charAt(i) == ')') {
++i;
return true;
}
}
}

return false;
}

private static boolean id() {

if (i < s.length() && s.charAt(i) >= 'a' && s.charAt(i) <= 'c') {
++i;
return true;
}

return false;
}

private static String s;
private static int i;
}

[mtyoung]

x ? y : z
if x then y else z

[carolain79@hotmail.com]

Thanks..............