I am using the Point class (http://docs.oracle.com/javase/7/docs/api/java/awt/Point.html#equals%28java.lang.Object%29).
I check in
http://docs.oracle.com/javase/7/docs/api/java/awt/Point.html#equals%28java.lang.Object%29
it said the object parameter refers to the object to be compared with this Point2D, is that means point type is comparable?
Indeed they are comparable.
For me the two main giveaways are:
1) The fact that the equals() method has a section there at all means it was overridden. If it wasn't overriden it would merely gain a small mention in the section titled "Methods inherited from class java.lang.Object".
2) The description that states how they have chosen to define equality matches the description that we would need: "Two instances of Point2D are equal if the values of their x and y member fields, representing their position in the coordinate space, are the same."