Liskov Substitution Principle (LSP)

Subtypes must be substitutable for their base types.

Example: Consider a scenario with a base class Bird and a derived class Penguin.

// Violation of LSP
public class Bird {
    public void fly() {
        System.out.println("Flying");
    }
}

public class Penguin extends Bird {
    @Override
    public void fly() {
        throw new UnsupportedOperationException("Penguins can't fly");
    }
}

// Following LSP
public class Bird {
    public void move() {
        System.out.println("Moving");
    }
}

public class Penguin extends Bird {
    @Override
    public void move() {
        System.out.println("Swimming");
    }
}

public class Sparrow extends Bird {
    @Override
    public void move() {
        System.out.println("Flying");
    }
}

In this case, Penguin does not override fly because it doesn’t make sense for it. Instead, both Penguin and Sparrow override move, which can be either flying or swimming, respecting LSP.

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