2. Comparable <T> Interface

Answer:
"apple", "orange", "plum".
This is the order that compareTo() would place the strings.

Comparable<T> Interface

An interface consists of constants and method declarations. The Comparable<T> interface consists of just one method (and no constants):

int compareTo( T obj )                        
Compare the object running
                obj, which 
 is of type T. Return a 
 negative integer, zero, or a 
 positive integer, when he 
 object running the method is 
 less than, equal, or greater 
 than obj.

T stands for the type of the objects. If the objects are Strings, then T is String. Strings implement the Comparable<String> interface.

If an object is of a class that implements Comparable, then that object is less than, equal, or greater than any object of that class. compareTo() returns an integer to show which of these three relations hold.

Question 2:
Does compartTo() tell us enough?
If any two objects can be compared, and the result is less than, equal, or greater 
than is this enough to put a collection of objects in order?