1 /**
   2  * ChainOfResponsibilityPattern example
   3  */
   4 
   5 class Trouble {
   6     private int number;
   7     public Trouble(int number) {
   8         this.number = number;
   9     }
  10     public int getNumber() {
  11         return number;
  12     }
  13     public String toString() {
  14         return "[Trouble "+number+"]";
  15     }
  16 }
  17 
  18 abstract class Support {
  19     private String name;
  20     private Support next;
  21     public Support(String name) {
  22         this.name = name;
  23     }
  24     public Support setNext(Support next) {
  25         this.next = next;
  26         return next;
  27     }
  28     public final void support(Trouble trouble) {
  29         if(resolve(trouble)) {
  30             done(trouble);
  31         } else if(next != null) {
  32             next.support(trouble);
  33         } else {
  34             fail(trouble);
  35         }
  36     }
  37     public String toString() {
  38         return "["+name+"]";
  39     }
  40     protected abstract boolean resolve(Trouble trouble);
  41     protected void done(Trouble trouble) {
  42         System.out.println(trouble+" is resolved by "+this+".");
  43     }
  44     protected void fail(Trouble trouble) {
  45         System.out.println(trouble+" cannot be resolved.");
  46     }
  47 }
  48 
  49 class NoSupport extends Support {
  50     public NoSupport(String name) {
  51         super(name);
  52     }
  53     protected boolean resolve(Trouble trouble) {
  54         return false;
  55     }
  56 }
  57 
  58 class LimitSupport extends Support {
  59     private int limit;
  60     public LimitSupport(String name, int limit) {
  61         super(name);
  62         this.limit = limit;
  63     }
  64     protected boolean resolve(Trouble trouble) {
  65         if(trouble.getNumber() < limit) {
  66             return true;
  67         } else {
  68             return false;
  69         }
  70     }
  71 }
  72 
  73 class OddSupport extends Support {
  74     public OddSupport(String name) {
  75         super(name);
  76     }
  77     protected boolean resolve(Trouble trouble) {
  78         if(trouble.getNumber()%2 == 1) {
  79             return true;
  80         } else {
  81             return false;
  82         }
  83     }
  84 }
  85 
  86 class SpecialSupport extends Support {
  87     private int number;
  88     public SpecialSupport(String name, int number) {
  89         super(name);
  90         this.number = number;
  91     }
  92     protected boolean resolve(Trouble trouble) {
  93         if(trouble.getNumber() == number) {
  94             return true;
  95         } else {
  96             return false;
  97         }
  98     }
  99 }
 100 
 101 public class ChainOfResponsibilityTrouble {
 102     public static void main(String[] args) {
 103         Support alice = new NoSupport("Alice");
 104         Support bob = new LimitSupport("Bob", 100);
 105         Support charlie = new SpecialSupport("Charlie", 429);
 106         Support diana = new LimitSupport("Diana", 200);
 107         Support elmo = new OddSupport("Elmo");
 108         Support fred = new LimitSupport("Fred", 300);
 109 
 110         alice.setNext(bob).setNext(charlie).setNext(diana).setNext(elmo).setNext(fred);
 111         for(int i=0; i < 500; i+=33) {
 112             alice.support(new Trouble(i));
 113         }
 114     }
 115 }