7.1. The Object Class

java.lang.Object is the ancestor of all objects; it's the primordial class from which all other classes are ultimately derived. Methods defined in Object are therefore very important because they appear in every instance of any class, throughout all of Java. At last count, there were nine public methods in Object. Five of these are versions of wait( ) and notify( ) that are used to synchronize threads on object instances, as we'll discuss in Chapter 8. The remaining four methods are used for basic comparison, conversion, and administration.

Every object has a toString( ) method that is called implicitly when it's to be represented as a text value. PrintStream objects use toString( ) to print data, as discussed in Chapter 10. toString( ) is also used when an object is referenced in a string concatenation. Here are some examples: