Add all 23 GoF design pattern implementations

02-structural/bridge/Radio.java

@@ -0,0 +1,18 @@
+package bridge;
+// Concrete Implementor #2: Radio
+public class Radio implements Device {
+    private boolean on = false;
+    private int volume = 20;
+    private int channel = 1;
+    @Override public boolean isEnabled() { return on; }
+    @Override public void enable()  { on = true;  System.out.println("  [Radio] Powered ON");  }
+    @Override public void disable() { on = false; System.out.println("  [Radio] Powered OFF"); }
+    @Override public int  getVolume() { return volume; }
+    @Override public void setVolume(int percent) {
+        this.volume = Math.max(0, Math.min(100, percent));
+        System.out.println("  [Radio] Volume set to " + this.volume);
+    }
+    @Override public int    getChannel()       { return channel; }
+    @Override public void   setChannel(int ch) { this.channel = ch; System.out.println("  [Radio] Frequency -> " + ch); }
+    @Override public String getName()          { return "JBL Radio"; }
+}