What will be the output when executing this main? (单选)
public class Test {
public static void swapStrings(String x, String y) {
String temp = x;
x = y;
y = temp;
}
public static void main(String[] args) {
String a = "1";
String b = "2";
swapStrings(a, b);
System.out.println("a=" + a + " ,b=" + b);
}
}