Add all 23 GoF design pattern implementations (2026-06-13)

03-behavioral/chain-of-responsibility/SupportHandler.java

@@ -0,0 +1,31 @@
+package chain;
+
+/**
+ * Handler interface — defines the chain contract.
+ * Each handler knows its next handler and can either
+ * handle the request itself or pass it along.
+ */
+public abstract class SupportHandler {
+
+    private SupportHandler next;
+
+    public SupportHandler setNext(SupportHandler next) {
+        this.next = next;
+        return next;  // fluent API: h1.setNext(h2).setNext(h3)
+    }
+
+    // Template method: subclasses implement handle(); base manages chaining
+    public final void handleRequest(SupportTicket ticket) {
+        if (canHandle(ticket)) {
+            handle(ticket);
+        } else if (next != null) {
+            System.out.println("  [" + getClass().getSimpleName() + "] passing up...");
+            next.handleRequest(ticket);
+        } else {
+            System.out.println("  [UNHANDLED] No handler for: " + ticket);
+        }
+    }
+
+    protected abstract boolean canHandle(SupportTicket ticket);
+    protected abstract void handle(SupportTicket ticket);
+}