The Object Class in java

In Java, the Object class is a special class that is the root of the class hierarchy. Every class in Java is directly or indirectly derived from the Object class. This means that the Object class is the superclass for all Java classes, and it provides some fundamental methods that are available to all objects in Java.

Here are some key points about the Object class:

  1. Methods in the Object Class:
  • The Object class provides several methods that can be overridden by any class. Some of the commonly used methods include:
    • toString(): Returns a string representation of the object.
    • equals(Object obj): Indicates whether some other object is “equal to” this one.
    • hashCode(): Returns a hash code value for the object.
    • getClass(): Returns the runtime class of an object.
    • clone(): Creates and returns a copy of the object.
  1. Default Implementation:
  • The methods in the Object class have default implementations. However, these implementations may not be suitable for all classes.
  • It’s common for classes to override the toString() and equals(Object obj) methods to provide meaningful representations and custom equality checks for objects.
  1. Implicit Inheritance:
  • Since every class in Java inherits from Object, if a class does not explicitly extend another class, it implicitly extends Object.
  • For example: public class MyClass { // ... } This is equivalent to: public class MyClass extends Object { // ... }
  1. Usage of Object in Collections:
  • Collections in Java, such as ArrayList or HashMap, can hold objects of any type. Since all classes extend Object, collections can hold objects of diverse types.
   List<Object> myList = new ArrayList<>();

In the example above, both a String and an Integer can be added to the list because both types ultimately extend Object.

The Object class is fundamental to the Java language and provides a common interface for all classes. Understanding and utilizing the methods from the Object class is essential when designing and working with Java classes.

Object, defined by Java. All other classes are subclasses of Object. That is, Object is a superclass of all other classes. This means that a reference variable of type Object can refer to an object of any other class

Object defines the following methods, which means that they are available in every object

Table of object class

Object clone( )Creates a new object that is the same as the object being cloned
boolean equals(Object object)Determines whether one object is equal to another.
void finalize( )Called before an unused object is recycled.
Class getClass( )Obtains the class of an object at run time.
int hashCode( )Returns the hash code associated with the invoking object
void notify( )Resumes execution of a thread waiting on the invoking object.
void notifyAll( )Resumes execution of all threads waiting on the invoking object
String toString( )Returns a string that describes the object
void wait( )
void wait(long milliseconds)
void wait(long milliseconds,
int nanoseconds)
Waits on another thread of execution.

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