added chain of responsibility example

src/lab7_state/ex2/User.java

@@ -3,13 +3,13 @@ package lab7_state.ex2;
 import lab7_state.ex2.states.*;
 
 public class User {
-    private String name;
+    private final String name;
     private UserState currentState;
-    private UserState unregisteredState;
+    private final UserState unregisteredState;
-    private UserState registeredState;
+    private final UserState registeredState;
-    private UserState inMeetingState;
+    private final UserState inMeetingState;
-    private UserState waitingToSpeakState;
+    private final UserState waitingToSpeakState;
-    private UserState speakingState;
+    private final UserState speakingState;
 
     public User(String name) {
         this.name = name;

src/learn/simple_responsibility_chain/ConcreteHandler1.java

@@ -0,0 +1,19 @@
+package learn.simple_responsibility_chain;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ConcreteHandler1 extends Handler {
+    private final List<String> myAnimals = Arrays.asList("cat", "dog", "horse");
+
+    @Override
+    public void handleRequest(Request request) {
+        if (myAnimals.contains(request.getValue())) {
+            System.out.println("Request for " + request.getValue() + " handled by " + this);
+        } else {
+            if (successor != null) {
+                successor.handleRequest(request);
+            }
+        }
+    }
+}

src/learn/simple_responsibility_chain/ConcreteHandler2.java

@@ -0,0 +1,19 @@
+package learn.simple_responsibility_chain;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ConcreteHandler2 extends Handler {
+    private final List<String> myColors = Arrays.asList("red", "yellow", "blue");
+
+    @Override
+    public void handleRequest(Request request) {
+        if (myColors.contains(request.getValue())) {
+            System.out.println("Request for " + request.getValue() + " handled by " + this);
+        } else {
+            if (successor != null) {
+                successor.handleRequest(request);
+            }
+        }
+    }
+}

src/learn/simple_responsibility_chain/ConcreteHandler3.java

@@ -0,0 +1,17 @@
+package learn.simple_responsibility_chain;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ConcreteHandler3 extends Handler {
+    private final List<String> myNumbers = Arrays.asList("1", "2", "3");
+
+    @Override
+    public void handleRequest(Request request) {
+        if (myNumbers.contains(request.getValue())) {
+            System.out.println("Request for " + request.getValue() + " handled by " + this);
+        } else {
+            throw new RuntimeException("Request could not be handled");
+        }
+    }
+}

src/learn/simple_responsibility_chain/Handler.java

@@ -0,0 +1,11 @@
+package learn.simple_responsibility_chain;
+
+public abstract class Handler {
+    protected Handler successor;
+
+    public void setSuccessor(Handler successor) {
+        this.successor = successor;
+    }
+
+    public abstract void handleRequest(Request request);
+}

src/learn/simple_responsibility_chain/Main.java

@@ -0,0 +1,21 @@
+package learn.simple_responsibility_chain;
+
+public class Main {
+    public static void main(String[] args) {
+        Handler firstHandler = new ConcreteHandler1();
+        Handler secondHandler = new ConcreteHandler2();
+        Handler thirdHandler = new ConcreteHandler3();
+
+        firstHandler.setSuccessor(secondHandler);
+        secondHandler.setSuccessor(thirdHandler);
+
+        Request request1 = new Request("dog");
+        firstHandler.handleRequest(request1);
+
+        Request request2 = new Request("3");
+        firstHandler.handleRequest(request2);
+
+        Request request3 = new Request("house");
+        firstHandler.handleRequest(request3);
+    }
+}

src/learn/simple_responsibility_chain/Request.java

@@ -0,0 +1,13 @@
+package learn.simple_responsibility_chain;
+
+public class Request {
+    private String value;
+
+    public Request(String value) {
+        this.value = value;
+    }
+
+    public String getValue() {
+        return value;
+    }
+}