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

02-structural/composite/File.java

@@ -0,0 +1,27 @@
+package composite;
+
+/**
+ * Leaf — a single file. It has no children.
+ * getSize() returns its own size. print() shows its name.
+ *
+ * Notice: the File has no knowledge of directories or nesting.
+ * It just knows its own name and size.
+ */
+public class File implements FileSystemItem {
+
+    private final String name;
+    private final long size;
+
+    public File(String name, long sizeBytes) {
+        this.name = name;
+        this.size = sizeBytes;
+    }
+
+    @Override public String getName() { return name; }
+    @Override public long   getSize() { return size; }
+
+    @Override
+    public void print(String indent) {
+        System.out.printf("%s[FILE] %s (%,d bytes)%n", indent, name, size);
+    }
+}