Differences between == and .equals

Question

I'm rather new to Java programming and have learned that == can only be used to compare primitive types in Java (for example when comparing to int) and when comparing objects, one should use the .equals-method (that should be overloaded from the one in Object). This is because == compare the object's reference adress (is this correct?) For example:
Vector v1 = new Vector();
Vector v2 = new Vector();
v1.add("hello");
v2.add("hello");
System.out.println(v1 == v2);This program should print false, since v1 and v2 are different objects.
System.out.println(v1 == v1);should print true.
OK, so far so good. However, an experiment I've made clearly shows that there's an exception to this rule. When comparing objects of type String, you don't need to use .equals, == works perfectly. My question is why?

Answer 1

When comparing objects of type String, you
don't need to use .equals, == works perfectly. My
question is why?It doesn't work perfectly at all.
String literals
Don't confuse String's equals() method with the equality operator '=='. The == operator checks that two references refer to the same object. If you want to compare the contents of Strings (whether two strings contain the same character sequence), use equals(), e.g. if (str1.equals(str2))...
Example:String s1 = "foo";
String s2 = new String("foo");
System.out.println("s1 == s2: " + (s1 == s2)); // false
System.out.println("s1.equals(s2): " + (s1.equals(s2))); // trueFor more information, check out Comparison operators: equals() versus ==