feat(hw-03): implement Chain of Responsibility pattern

hw-03/project-root/app/src/main/java/org/example/App.java

@@ -5,6 +5,7 @@ package org.example;
 
 import org.example.adapter.*;
 import org.example.builder.*;
+import org.example.chain.*;
 
 public class App {
   public static void main(String[] args) {
@@ -14,6 +15,7 @@ public class App {
   private static void run() {
     checkAdapterPattern();
     checkBuilderPattern();
+    checkChainPattern();
   }
 
   private static void checkAdapterPattern() {
@@ -29,4 +31,12 @@ public class App {
 
     System.out.println(product);
   }
+
+  private static void checkChainPattern() {
+    Handler handler = new ConcreteHandlerA();
+    handler.setNext(new ConcreteHandlerB());
+
+    handler.handle(42);
+    handler.handle("Hello");
+  }
 }

hw-03/project-root/app/src/main/java/org/example/chain/AbstractHandler.java

@@ -0,0 +1,17 @@
+package org.example.chain;
+
+/** Abstract Handler */
+public abstract class AbstractHandler implements Handler {
+  private Handler next;
+
+  @Override
+  public void setNext(Handler handler) {
+    this.next = handler;
+  }
+
+  protected void handleNext(Object request) {
+    if (next != null) {
+      next.handle(request);
+    }
+  }
+}

hw-03/project-root/app/src/main/java/org/example/chain/ConcreteHandlerA.java

@@ -0,0 +1,14 @@
+package org.example.chain;
+
+/** Concrete Handler A */
+public class ConcreteHandlerA extends AbstractHandler {
+
+  @Override
+  public void handle(Object request) {
+    if (request instanceof Integer) {
+      System.out.println("ConcreteHandlerA обработал int: " + request);
+    } else {
+      handleNext(request);
+    }
+  }
+}

hw-03/project-root/app/src/main/java/org/example/chain/ConcreteHandlerB.java

@@ -0,0 +1,14 @@
+package org.example.chain;
+
+/** Concrete Handler B */
+public class ConcreteHandlerB extends AbstractHandler {
+
+  @Override
+  public void handle(Object request) {
+    if (request instanceof String) {
+      System.out.println("ConcreteHandlerB обработал String: " + request);
+    } else {
+      handleNext(request);
+    }
+  }
+}

hw-03/project-root/app/src/main/java/org/example/chain/Handler.java

@@ -0,0 +1,8 @@
+package org.example.chain;
+
+/** Handler */
+public interface Handler {
+  void setNext(Handler handler);
+
+  void handle(Object request);
+}