Pass By Value And Strings

Below is the snippet of code

public static void main(String[] args) throws Exception {
String s = "oldString";
reverse(s);
System.out.println(s); // oldString
}
public static void modifyString(String s) {
s = "newString";
System.out.println(s); // newString
}

I thought the first print statement would print "newString" as String is an object, and when we pass objects between methods, changing state of the object in any method reflects across the methods.