JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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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

Other Exception Handling Examples

Knowledge Centre
What is abstract class or abstract method?
We cannot create instance for an abstract class. We can able to create instance for its subclass only. By specifying abstract keyword just before class, we can make a class as abstract class.

public abstract class MyAbstractClass{

}

Abstract class may or may not contains abstract methods. Abstract method is just method signature, it does not containes any implementation. Its subclass must provide implementation for abstract methods. Abstract methods are looks like as given below:

public abstract int getLength();
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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.
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