Code snippet 1 for Interface Segregation Principle

ISP1.java

// Interface Tasks
interface Tasks {
    void code();
    void test();
}

// Class Assignee
abstract class Assignee implements Tasks {}

// Developer is an Assingee
class Developer extends Assignee {
    @Override
    public void code() { System.out.println("I can code!"); }

    @Override
    public void test() {
        System.out.println("throw new UnsupportedOperationException('I can\'t test!')"); }
}

// Tester is an Assingee
class Tester extends Assignee {
    @Override
    public void code() {
        System.out.println("throw new UnsupportedOperationException('I can\'t code!');"); }

    @Override
    public void test() { System.out.println("I can test!"); }
}

public class ISP1 {
    public static void main(String[] args) {
        Assignee coder = new Developer();
        Assignee tester = new Tester();

        coder.code();
        coder.test();
        System.out.println();
        tester.test();
        tester.code();
    }
}

Program output:

I can code!
throw new UnsupportedOperationException('I can't test!')

I can test!
throw new UnsupportedOperationException('I can't code!');