Chain of Responsibility Pattern

abstract class Handler {

    // next handler in chain of handlers
    protected Handler next;

    // Derived classes set this property in their constructor.
    // Used to decide what handler class will do the job
    protected int msgImportance;

    // used to construct handler chain of any length
    public void setNext(Handler next) {
        this.next = next;
    }

    // Client code calls only this method (requesting to do the job).
    // Depending on c, this method decides
    // this class handles the request, or we forward handling to next Handler in
    // chain
    public void handleMessage(String msg, int msgPriority) {
        // if this handler class fits criteria (msgImportance) - let it do the job!
        if (msgPriority <= msgImportance) {
            doRealMessageHandling(msg);
            return; // comment out to call subsequent handlers anyway (for other processing needs)
        }

        // proceed to next handler in the chain
        if (next != null) {
            next.handleMessage(msg, msgPriority);
        }
    }

    protected abstract void doRealMessageHandling(String msg);

}

class SpamMessageHandler extends Handler {

    public SpamMessageHandler(int msgImportance) {
        this.msgImportance = msgImportance;
    }

    @Override
    protected void doRealMessageHandling(String msg) {
        System.out.println("processed SPAM successfully!" + " Msg is: " + msg);
    }

}

class RegularMessageHandler extends Handler {

    public RegularMessageHandler(int msgImportance) {
        this.msgImportance = msgImportance;
    }

    @Override
    protected void doRealMessageHandling(String msg) {
        System.out.println("processed RegularMessage successfully!" + " Msg is: " + msg);
    }

}

class ImportantMessageHandler extends Handler {

    public ImportantMessageHandler(int msgImportance) {
        this.msgImportance = msgImportance;
    }

    @Override
    protected void doRealMessageHandling(String msg) {
        System.out.println("processed ImportantMessage successfully!" + " Msg is: " + msg);
    }

}

class LoveMessageHandler extends Handler {

    public LoveMessageHandler(int msgImportance) {
        this.msgImportance = msgImportance;
    }

    @Override
    protected void doRealMessageHandling(String msg) {
        System.out.println("processed LoveMessage successfully!" + " Msg is: " + msg);
    }

}

public class Driver {

    public static void main(String[] args) {

        // instantiate handlers and specify mask.
        // Based on mask handler decides to handle task
        // or to delegate handling to next handler in chain
        Handler myHandler, handler2, handler3, handler4;
        myHandler = new SpamMessageHandler(10);
        handler2 = new RegularMessageHandler(100);
        handler3 = new ImportantMessageHandler(777);
        handler4 = new LoveMessageHandler(999);

        // hook up handler chain
        myHandler.setNext(handler2); // first handler in chain - call this one!
        handler2.setNext(handler3);
        handler3.setNext(handler4);

        // ask chain (thru Handler interface) to do the job
        myHandler.handleMessage("Some argument", 700); // ImportantMessage handler fits
        myHandler.handleMessage("Some argument", 1); // SpamMessage handler fits
        myHandler.handleMessage("Some argument", 900); // LoveMessage handler fits

    }
}