Chain of Responsibility pattern JAVA code example

ChainOfResponsibility.java

class Job {
    private String details;

    public Job(String details) {
        this.details = details;
    }

    public String requirements() {
        return this.details;
    }
}

class StackDetector {
    public static boolean match(String stack, String details) {
        return details.indexOf(stack) > -1;
    }
}

abstract class Handler {
    protected Handler successor;

    public void forwardToSuccessor(Job job) {
        if (this.successor != null)
            this.successor.handle(job);
    }

    public abstract void handle(Job job);
}

class PHPStack extends Handler {
    public PHPStack(Handler successor) {
        this.successor = successor;
    }

    public void handle(Job job) {
        if (StackDetector.match("PHP", job.requirements()))
            // Notify PHP developers
            System.out.println("PHP Stack");
        else
            this.forwardToSuccessor(job);
    }
}

class JavaScriptStack extends Handler {
    public JavaScriptStack(Handler successor) {
        this.successor = successor;
    }

    public void handle(Job job) {
        if (StackDetector.match("JavaScript", job.requirements()))
            // Notify JavaScript developers
            System.out.println("JavaScript Stack");
        else
            this.forwardToSuccessor(job);
    }
}

class JavaStack extends Handler {
    public JavaStack(Handler successor) {
        this.successor = successor;
    }

    public void handle(Job job) {
        if (StackDetector.match("Java", job.requirements()))
            // Notify Java developers
            System.out.println("Java Stack");
        else
            this.forwardToSuccessor(job);
    }
}

class DoNothing extends Handler {
    public void handle(Job job) {
        // Do nothing
        System.out.println("The request object is unhandled");
    }
}

class Main {
    public static void main(String[] args) {
        // Chain of Job handler objects
        Handler doNothing = new DoNothing();
        Handler javaStack = new JavaStack(doNothing);
        Handler javaScriptStack = new JavaScriptStack(javaStack);
        Handler phpStack = new PHPStack(javaScriptStack);

        // The request object to be handled
        Job job = new Job("PHP"); // Try changing the value to Python, JavaScript or Java

        // Starts handling the Job object
        phpStack.handle(job);
    }
}