What is the output of the following code?

```
public class Test {
public static void main(String[] args) {
String s1 = new String("Welcome to Java!");
String s2 = s1.toUpperCase();

if (s1 == s2)
System.out.println("s1 and s2 reference to the same String object");
else if (s1.equals(s2))
System.out.println("s1 and s2 have the same contents");
else
System.out.println("s1 and s2 have different contents");
}
}
```
a. s1 and s2 reference to the same String object
b. s1 and s2 have the same contents
c. s1 and s2 have different contents

c. s1 and s2 have different contents