In the Java programming language, the top of the class hierarchy is occupied by the Object class. Every class you define, whether it is a simple String or a complicated class of your own design, inherits from the java.lang.Object class by default.
This design choice guarantees that all objects in a Java application have a set of fundamental operations in common. The object class methods in Java are not just a programming necessity; it is the key to effective memory management, thread safety, and equality tests. Learn object class methods comprehensively in our Java training in Chennai.
What is the Object Class?
If a class does not explicitly extend another class by using the “extends” keyword, then it becomes a subclass of the Object class by default. This means that the methods of the object class in Java are accessible to every single object in your world.
The Object class is the “glue” that makes it possible for the Java Virtual Machine (JVM) to work with objects at a low level. For example, when you use System.out.println(myObject), Java internally invokes the toString() method of the Object class.
Comprehensive List of Object Class Methods in Java
Here is the list of object class in Java. These methods define the lifecycle of an object, its movement, and its death in the Java virtual machine. Below is a comprehensive list of the object class methods.
1. toString() Method
The toString() method is used to convert the object to a string. By default, the method returns the class name and the @ symbol followed by the unsigned hexadecimal representation of the hash code.
Code Snippet:
public class Employee {
String name = “Gethsiyal”;
@Override
public String toString() {
return “Employee Name: ” + name;
}
public static void main(String[] args) {
Employee emp = new Employee();
System.out.println(emp.toString()); // Output: Employee Name: Gethsiyal
}
}
2. hashCode() Method
The JVM generates a unique integer for every object called the hash code. This is mostly used in hashing-based objects such as HashMap, HashSet, and Hashtable.
Code Snippet:
Employee emp = new Employee();
System.out.println(“Hashcode: ” + emp.hashCode());
3. equals(Object obj) Method
The equals() method is used to compare the equality of two objects. By default, the method compares the objects using the ‘==’ operator. However, in professional development, the method is overridden to compare the content of the objects.
Code Snippet:
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null || getClass() != obj.getClass()) return false;
Employee employee = (Employee) obj;
return name.equals(employee.name);
}
4. getClass() Method
This is a final method in Java. This method is used to retrieve the Class object of the current instance.
Code Snippet:
Employee emp = new Employee();
System.out.println(“Class Name: ” + emp.getClass().getName());
5. clone() Method
This method creates and then returns a clone of the object. The class must implement the Cloneable interface, or this method will throw a CloneNotSupportedException.
Code Snippet:
public class Project implements Cloneable {
String pName = “Java Frameworks”;
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
6. finalize() Method
Note: Deprecated since Java 9, but still very important for the understanding of legacy systems.
This method is called by the garbage collector before the object is destroyed.
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Methods for Thread Synchronization
There are three specific methods of the object class in Java, which are meant for inter-thread communication. These methods must be called from a synchronized context.
wait(), notify(), and notifyAll()
wait(): Instructs the current thread to release the lock and sleep, waiting to be woken up by another thread.
- notify(): Wakes up one thread waiting on the monitor for this object.
- notifyAll(): Wakes up all threads waiting on the monitor for this object.
Code Snippet:
synchronized(obj) {
while (condition) {
obj.wait(); // Releases lock and waits
}
// Perform action
obj.notify(); // Wakes up another thread
}
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Best Practices of Methods of Object Class in Java
The best practices for object class methods in Java include the following:
- Override toString(): This should always be overridden for easier debugging and logging.
- The Equals/HashCode Contract: This contract states that if you have overridden the equals() method, you should also override the hashCode() method. This is necessary to ensure that two objects that are equal have the same hash code.
- Avoid finalize(): This is not necessary anymore. Instead, you should use the try-with-resources statement or the Cleaner.
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Conclusion
The Object class methods are the silent engine under the hood of every Java application. By providing a standardized set of object class methods in Java, it enables seamless data comparison, efficient storage of objects in collections, and complex communication in multi-threaded environments. The object class methods in Java must be mastered by every Java developer who aspires to build professional-grade applications.
Are you ready to see these methods in action in a real-world application? Head over to our software training institute in Chennai and explore Java courses to start building enterprise-level applications today!
