java.lang · java.base · since Java 1.0

Object

declaration

public class Object

The root of the class hierarchy. Every class inherits its identity, equality, hashing, and monitor methods — and overriding them correctly is a contract-bound discipline.

equals/hashCode/toString are the overridable trio — see the Object Contracts topic
wait/notify/notifyAll operate on the object monitor (legacy; prefer java.util.concurrent)
getClass() returns the runtime Class object

Key methods

`boolean equals(Object obj)`	Reference equality by default; override for value equality (with hashCode).
`int hashCode()`	Identity-based by default; must be consistent with equals.
`String toString()`	ClassName@hexHash by default; always override for diagnostics.
`Class<?> getClass()`	Runtime class, the reflection entry point.
`void wait() / void notify() / void notifyAll()`	Monitor coordination — superseded by concurrency utilities.
`protected Object clone()`	Field-by-field copy behind Cloneable; broken design, prefer copy constructors (EJ 13).