Create custom or user defined unchecked exception in java (example)

Create a user defined exception in java.
Create a custom exception, by extending unchecked exceptions.
1. We will create CustomArithmeticException by extending ArithmeticException class
2. We will create CustomNullPointerException by extending NullPointerException class.

Exception class hierarchy in java

User defined custom exception — Fig 1: Custom NullPointerException & ArithmeticException

Program – Custom user defined arithmetic & nullpointer exception

1.) CustomArithmeticException Class:

Create CustomArithmeticException class, by extending ArithmeticException exception class.

package org.learn.exception;
 
public class CustomArithmeticException extends ArithmeticException {
 
    private static final long serialVersionUID = 652325545058196579L;
 
    public CustomArithmeticException(String s) {
        super(s);
    }
}

2.) CustomNullPointerExceptionClass:

Create CustomNullPointerException class by extending NullPointerException class.

package org.learn.exception;
 
public class CustomNullPointerException extends NullPointerException {
 
    private static final long serialVersionUID = 5627096569547521249L;
 
    public CustomNullPointerException(String s) {
        super(s);
    }
}

3.) ExceptionClient Class:

ExceptionClient class containing main method
We are simulating CustomArithmeticException & CustomNullPointerException.
We are catching CurstomArithmeticException & CustomNullPointerException.

package org.learn.client;
 
import org.learn.exception.CustomArithmeticException;
import org.learn.exception.CustomNullPointerException;
 
public class ExceptionClient {
    public static void main(String[] args) {
 
        // 1. Throw & catch ArithmeticException
        try {
            simulateArithmeticException();
        } catch (CustomArithmeticException exp) {
            System.out.println("1. Caught MyArithmeticException:"+exp.getMessage());
        }
 
        // 2. Throw & catch NullPointerException        
        try {
            simulateNullPointerException();
        } catch (CustomNullPointerException exp) {
            System.out.println("2. Caught MyNullPointerException : "+exp.getMessage());
        }
    }
     
    private static void simulateArithmeticException() {
        int divByZero = 0;
        try {
            divByZero = 100 / 0;
            System.out.println("divByZero value:"+divByZero);
        } catch (ArithmeticException exp) {
            throw new CustomArithmeticException("ArithmeticException occurred : " + exp.getMessage());
        }
    }
     
    @SuppressWarnings("null")
    private static void simulateNullPointerException() {
        try {
            String blankString = null;
            System.out.println("String length :"+blankString.length());
            //simulating null pointer exception.
        } catch (NullPointerException exp) {
            throw new CustomNullPointerException("NullPointerException occurred ");
        }
    }
}

Output – Custom user defined arithmetic & nullPointer exception

1. Caught MyArithmeticException:ArithmeticException occurred : / by zero
2. Caught MyNullPointerException : NullPointerException occurred 

Exception class hierarchy in java

Program – Custom user defined arithmetic & nullpointer exception

1.) CustomArithmeticException Class:

2.) CustomNullPointerExceptionClass:

3.) ExceptionClient Class:

Output – Custom user defined arithmetic & nullPointer exception

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