Garbage Collection

• Garbage collection is the process of destroying unused objects
• In Languages like C/C++ we use free() or delete() to delete unused objects
• But in C/C++ user manually need to delete those objects but most of them don't do this.
• But in Java, this process is automatically done by the garbage collector in JVM
• It makes java memory efficient

Methods in garbage collection

1. gc()

Used to start the cleanup process

Syntax

public static void gc() {
}

2. finalize()

This method is called each time when an object is garbage collected

Syntax

protected void finalize() {
}

An object can be deleted in 3 ways. They are

1. By assigning NULL
2. By assigning a reference to another object
3. Using an anonymous object

1. By assigning NULL

Example ob = new Example();
ob = null;

Example

public class Example {  
  
 public void finalize() {
   System.out.println("object is garbage collected");
 }  
 
 public static void main(String args[]){  
  Example ob = new Example();  
  ob = null;  
  System.gc();  
 }  
}  

check output here

2. By assigning a reference to another object

Example ob1 = new Example();
Example ob2 = new Example();
ob1 = ob2;

Example

public class Example {  
  
 public void finalize() {
   System.out.println("object is garbage collected");
 }  
 
 public static void main(String args[]){  
  Example ob1 = new Example();
  Example ob2 = new Example(); 
  ob1 = ob2;  
  System.gc();  
 }  
}  

check output here

3. Using an anonymous object

new Example ();

Example

public class Example {  
  
 public void finalize() {
   System.out.println("object is garbage collected");
 }  
 
 public static void main(String args[]){  
  new Example();
  System.gc();  
 }  
}  

check output here