How do I implement the State Pattern in Java?

How do I implement the State Pattern in Java?

The State Pattern allows an object to alter its behavior when its internal state changes. Would you like a code example?

Yes, please provide a simple code example.

Sure! Here's a basic example:

interface State {
    void handleRequest();
}

class ConcreteStateA implements State {
    public void handleRequest() {
        System.out.println("Handling request in State A.");
    }
}

class ConcreteStateB implements State {
    public void handleRequest() {
        System.out.println("Handling request in State B.");
    }
}

class Context {
    private State state;

    public void setState(State state) {
        this.state = state;
    }

    public void request() {
        state.handleRequest();
    }
}

This code defines a context that can change its state.

How do I switch between states in this example?

You can switch states by calling setState() on the Context object. For example:

Context context = new Context();
context.setState(new ConcreteStateA());
context.request(); // Outputs: Handling request in State A.

context.setState(new ConcreteStateB());
context.request(); // Outputs: Handling request in State B.