JAVA EXAMPLE PROGRAMS

How to Create Java Custom Exception

Sometimes it is required to develop meaningful exceptions based on application requirements. We can create our own exceptions by extending 'Exception' class. Below example shows how to create custom exception by extending Exception class.

Java Custom Exception Sample Code

Code:

package com.myjava.exceptions;

public class MyOwnException {
    public static void main(String[] a){
        try{
            MyOwnException.myTest(null);
        } catch(MyAppException mae){
            System.out.println("Inside catch block: "+mae.getMessage());
        }
    }
    
    static void myTest(String str) throws MyAppException{
        if(str == null){
            throw new MyAppException("String val is null");
        }
    }
}

class MyAppException extends Exception {

	private String message = null;

	public MyAppException() {
		super();
	}

	public MyAppException(String message) {
		super(message);
		this.message = message;
	}

	public MyAppException(Throwable cause) {
		super(cause);
	}

	@Override
	public String toString() {
		return message;
	}

	@Override
	public String getMessage() {
		return message;
	}
}

Example Output

Inside catch block: String val is null

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Knowledge Centre

Interface and its usage

Interface is similar to a class which may contain method's signature only but not bodies and it is a formal set of method and constant declarations that must be defined by the class that implements it. Interfaces are useful for declaring methods that one or more classes are expected to implement, capturing similarities between unrelated classes without forcing a class relationship and determining an object's programming interface without revealing the actual body of the class.

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-- William Arthur Ward

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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.