added composite example

src/learn/simple_composite/Component.java

@@ -0,0 +1,5 @@
+package learn.simple_composite;
+
+public interface Component {
+    void operation();
+}

src/learn/simple_composite/Composite.java

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+package learn.simple_composite;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Composite implements Component {
+    private List<Component> children = new ArrayList<>();
+
+    @Override
+    public void operation() {
+        for (Component component : children) {
+            component.operation();
+        }
+    }
+
+    public void add(Component component) {
+        children.add(component);
+    }
+
+    public void remove(Component component) {
+        children.remove(component);
+    }
+
+    public Component getChild(int index) {
+        return children.get(index);
+    }
+}

src/learn/simple_composite/Leaf.java

@@ -0,0 +1,8 @@
+package learn.simple_composite;
+
+public class Leaf implements Component {
+    @Override
+    public void operation() {
+        System.out.println("Leaf operation" + this);
+    }
+}

src/learn/simple_composite/Main.java

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+package learn.simple_composite;
+
+public class Main {
+    public static void main(String[] args) {
+        Composite root = new Composite();
+        Composite node1 = new Composite();
+        Composite node2 = new Composite();
+        Leaf l1 = new Leaf();
+        Leaf l2 = new Leaf();
+
+        root.add(node1);
+        node1.add(node2);
+        node2.add(l1);
+        node2.add(l2);
+
+        root.operation();
+    }
+}