Java Object Class

 Object Class

It is the parent class of all classes in Java.

Method	Description
public final Class getClass()	returns the Class class object of this object. The Class class can further be used to get the metadata of this class.
public int hashCode()	returns the hashcode number for this object.
public boolean equals(Object obj)	compares the given object to this object.
protected Object clone() throws CloneNotSupportedException	creates and returns the exact copy (clone) of this object.
public String toString()	returns the string representation of this object.
public final void notify()	wakes up a single thread, waiting on this object's monitor.
public final void notifyAll()	wakes up all the threads, waiting on this object's monitor.
public final void wait(long timeout)throws InterruptedException	causing the current thread to wait for the specified milliseconds until another thread notifies (invokes notify() or notifyAll() method).
public final void wait(long timeout, int nanos)throws InterruptedException	causes the current thread to wait for the specified milliseconds and nanoseconds until another thread notifies (invokes notify() or notifyAll() method).
public final void wait()throws InterruptedException	causing the current thread to wait until another thread notifies (invokes notify() or notifyAll() method).
protected void finalize()throws Throwable	is invoked by the garbage collector before the object is being garbage collected.

Example 01:

package com.java.ObjectClass;

public class ObjectClassExample {

private String name;

private int age;

public ObjectClassExample(String name, int age) {

this.name = name;

this.age = age;

}

@Override

public String toString() {

return "ObjectClassExample{name='" + name + "', age=" + age + "}";

}

@Override

public boolean equals(Object obj) {

if (this == obj) {

return true; // Check if the same reference

}

if (obj == null || getClass() != obj.getClass()) {

return false; // Check if types are different

}

ObjectClassExample other = (ObjectClassExample) obj;

return age == other.age && (name != null ? name.equals(other.name) : other.name == null);

}

@Override

public int hashCode() {

int result = name != null ? name.hashCode() : 0;

result = 31 * result + age;

return result;

}

public static void main(String[] args) {

ObjectClassExample obj1 = new ObjectClassExample("Alice", 30);

ObjectClassExample obj2 = new ObjectClassExample("Alice", 30);

ObjectClassExample obj3 = new ObjectClassExample("Bob", 25);

// Using toString()

System.out.println("obj1: " + obj1.toString());

System.out.println("obj2: " + obj2);

// Using equals()

System.out.println("obj1 equals obj2: " + obj1.equals(obj2)); // true

System.out.println("obj1 equals obj3: " + obj1.equals(obj3)); // false

// Using hashCode()

System.out.println("obj1 hashCode: " + obj1.hashCode());

System.out.println("obj2 hashCode: " + obj2.hashCode());

System.out.println("obj3 hashCode: " + obj3.hashCode());

}

}