I was wondering since every object extends from Object Class ..so if one class extends from another it already extends from the Object class. Shouldnt this line be more Java doesnt support user defined multiple inheritance..
No, that would be like saying that Kitty is two different things at once because he's both a cat and an animal. But he isn't two different things at once, because Cat is-a Animal. Now to say that Kitty were simultaneously a cat and a horse, that would be like multiple inheritance.
I have about 70 books on my shelf on the Java programming language (a bit excessive I know) starting with one published around 1997 and they all say Java does not support Multiple Inheritance. Now they might all be wrong but...
Java supports only interface inheritance. You may inherit zero or more interfaces, which have only abstract (no impl) methods. Java does not support multiple concrete inheritance. A Java class has one and only one superclass, not zero, not two. The only exception to this rule is for java.lang.Object, which has zero superclasses. A Java class inherits from java.lang.Object, directly or indirectly, through concrete inheritance. Each leaf node of the tree has one and only one parent.
Frankly, I don't understand why: a) this trivial concept is so difficult to grasp b) this concept continues to be the focus of discussion even after the language has matured