All the classes in Java that you have defined so far are subclasses by default whether or not you have specified the superclass. The class which all classes in Java are descendent of (directly or indirectly) is java .lang. Object class. So each class inherits the instance methods of Object class. It is important to be familiar with the methods provided by the Object class so that you can use them in your class.
public String toString (): This method returns a string representation of an object. The default implementation returns the name of the class followed by , @' and the hexadecimal representation for the object. You can override this method in your classes, to return your own String object for your class.
public boolean equals (Object obj): This method compares two objects for equality and returns true if they are equal and false otherwise.
public final class getClass (): This method returns a class Object (package Java language that contains information about the object's type, such as its classname, its superclass and the interfaces it implements.
Public int hashcode (): This method returns the hashcode value associated with the invoking object.
protected Object clone() throws CloneNotSupportedException : This method creates a copy of the object on which it is called.
Protected void finalize() throws Throwable: This method is called by the garbage collector on an object that becomes garbage. An object becomes garbage when there are no more references to it.
class Rectangle extends Object
private double length,breadth;
Rectangle(double x,double y)
length = x ;
breadth = y ;
public void area()
System.out.println("Area of Rectangle is = " + breadth);
public void circumference()
System.out.println("Circumferen of Rectangle is= "+2*(length+breadth));
public static void main(String args)
Rectangle r = new Rectangle(10,20);
Rectangle rl = new Rectangle(10,20);
System.out.println("String Representation = " + r.toString());
System.out.println("Class Name = " + r.getClass());
System.out.println("Hash Code = " + r.hashCode());
System.out.println("r.rquals(rl) = " + r.equals(rl));