Object class in Java
The Object class is the parent class of all the classes in java by default. In other words, it is the topmost class of java.
The Object class is beneficial if you want to refer any object whose type you don't know. Notice that parent class reference variable can refer the child class object, know as upcasting.
Let's take an example, there is getObject() method that returns an object but it can be of any type like Employee,Student etc, we can use Object class reference to refer that object. For example:
The Object class provides some common behaviors to all the objects such as object can be compared, object can be cloned, object can be notified etc.
public class Object
The Object class is the root class in Java from which every class implicitly inherits.
Syntax
Here is the syntax:
Constructor Summary
The Object class provides a default constructor to create a new object instance.
Syntax
The following is the syntax of invoking default constructor of Object class:
Constructor Detail
The constructor of the Object class has no parameters and initializes a new instance of the object.
Syntax
The following is the syntax of constructor detail:
Methods of Object class
The following tables lists the commonly used methods of object class:
| 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 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 | causes 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 | causes 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 object is being garbage collected. |
Examples of Object Class Methods
Here are examples of commonly used methods of the Object class:
Example 1: Use of toString() Method
The following example demonstrates the toString() method that returns a string representation of the object:
Output:
Object as String: java.lang.Object@1b6d3586
Example 2: Use of equals() Method
The following example demonstrates the equals() method that checks whether two objects are equal:
Output:
Are the strings equal? True
Example 3: Use of hashCode() Method
The following example demonstrates the hashCode() method that returns the hash code value of an object.
Output:
Hash code of the object: 460141958
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