Exception Handling with Method Overriding in Java

There are many rules if we talk about method overriding with exception handling.

Some of the rules are listed below:

If the superclass method does not declare an exception
- If the superclass method does not declare an exception, subclass overridden method cannot declare the checked exception but it can declare unchecked exception.
If the superclass method declares an exception
- If the superclass method declares an exception, subclass overridden method can declare same, subclass exception or no exception but cannot declare parent exception.

If the superclass method does not declare an exception

Rule 1: If the superclass method does not declare an exception, subclass overridden method cannot declare the checked exception.

Let's consider following example based on the above rule.

TestExceptionChild.java

import java.io.*;  
class Parent{ 

  // defining the method 
  void msg() {
    System.out.println("parent method");
    }  
}  
  
public class TestExceptionChild extends Parent{  

  // overriding the method in child class
  // gives compile time error
  void msg() throws IOException {  
    System.out.println("TestExceptionChild");  
  }

  public static void main(String args[]) {  
   Parent p = new TestExceptionChild();  
   p.msg();  
  }  
}  

Output:

Exception Handling with Method Overriding in Java

Rule 2: If the superclass method does not declare an exception, subclass overridden method cannot declare the checked exception but can declare unchecked exception.

TestExceptionChild1.java

import java.io.*;  
class Parent{  
  void msg() {
    System.out.println("parent method");
  }  
}  
  
class TestExceptionChild1 extends Parent{  
  void msg()throws ArithmeticException {  
    System.out.println("child method");  
  }  

  public static void main(String args[]) {  
   Parent p = new TestExceptionChild1();  
   p.msg();  
  }  
} 

Output:

If the superclass method declares an exception

Rule 1: If the superclass method declares an exception, subclass overridden method can declare the same subclass exception or no exception but cannot declare parent exception.

Example in case subclass overridden method declares parent exception

TestExceptionChild2.java

import java.io.*;  
class Parent{  
  void msg()throws ArithmeticException {
    System.out.println("parent method");
  }  
}  
  
public class TestExceptionChild2 extends Parent{  
  void msg()throws Exception {
    System.out.println("child method");
  }  
  
  public static void main(String args[]) {  
   Parent p = new TestExceptionChild2();  
   
   try {  
   p.msg();  
   }
   catch (Exception e){} 

  }  
}   

Output:

Example in case subclass overridden method declares same exception

TestExceptionChild3.java

import java.io.*;  
class Parent{  
  void msg() throws Exception {
    System.out.println("parent method");
  }  
}  
  
public class TestExceptionChild3 extends Parent {  
  void msg()throws Exception {
    System.out.println("child method");
  }  
  
  public static void main(String args[]){  
   Parent p = new TestExceptionChild3();  
   
   try {  
   p.msg();  
   }
   catch(Exception e) {}  
  }  
}  

Output:

Example in case subclass overridden method declares subclass exception

TestExceptionChild4.java

import java.io.*;  
class Parent{  
  void msg()throws Exception {
    System.out.println("parent method");
  }  
}  
  
class TestExceptionChild4 extends Parent{  
  void msg()throws ArithmeticException {
    System.out.println("child method");
  }  
  
  public static void main(String args[]){  
   Parent p = new TestExceptionChild4();  
   
   try {  
   p.msg();  
   }
   catch(Exception e) {}  
  }  
}  

Output:

Example in case subclass overridden method declares no exception

TestExceptionChild5.java

import java.io.*;  
class Parent {  
  void msg()throws Exception{
    System.out.println("parent method");
  }  
}  
  
class TestExceptionChild5 extends Parent{  
  void msg() {
    System.out.println("child method");
  }  
  
  public static void main(String args[]){  
   Parent p = new TestExceptionChild5();  
   
   try {  
   p.msg();  
   }
   catch(Exception e) {}
     
  }  
}   

Output: