Methods from Object class can be grouped into two categories.
The ready-to-use methods have been implemented in the Object class.
Methods that fall into this category are getClass(), notify(), notifyAll(), and wait().
The not-ready-to-use Methods have a default implementation in the Object class. You have to reimplement (override) them to get proper usage.
Methods that fall into this category are toString(), equals(), hashCode(), clone(), and finalize().
List of Methods in the Object Class with Their Brief Description
| Method | Implemented | Customizable | Description |
|---|---|---|---|
| public String toString() | Yes | Yes | It returns a string representation of an object. Typically, it is used for debugging purpose. |
| public boolean equals(Object obj) | Yes | Yes | It is used to compare two objects for equality. |
| public int hashCode() | Yes | Yes | It returns a hash code (an integer) value of an object. |
| protected Object clone() throws CloneNotSupportedException | No | Yes | It is used to make a copy of an object. |
| protected void finalize() throws Throwable | No | Yes | It is called by the garbage collector before an object is destroyed. |
| public final Class getClass() | Yes | No | It returns a reference to the Class object of the object. |
| public final void notify() | Yes | No | Notifies one thread in the wait queue of the object. |
| public final void notifyAll() | Yes | No | Notifies all threads in the wait queue of the object. |
| public final void wait() throws InterruptedException | Yes | No | Makes a thread wait in the wait queue of the object with a timeout. |
| public final void wait(long timeout) throws InterruptedException | Yes | No | Makes a thread wait in the wait queue of the object without a timeout. |
| public final void wait (long timeout, int nanos) throws InterruptedException | Yes | No | Makes a thread wait in the wait queue of the object with a timeout. |