Add all 23 GoF design pattern implementations

02-structural/composite/File.java

@@ -0,0 +1,20 @@
+package composite;
+/**
+ * Leaf — a single file with no children.
+ * getSize() returns its own bytes. print() outputs a single line.
+ * No knowledge of directories or nesting exists in this class.
+ */
+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);
+    }
+}