public class HungrySingleton {
	private static HungrySingleton instance = new HungrySingleton();
	private HungrySingleton() {
	}
	public static HungrySingleton getInstance() {
		return instance;
	}
}

publci class LazySingleton {
	private static LazySingleton instance = null;
	private LazySingleton() {
	
	}
	public static synchronized LazySingleton getInstance() {
		if (instance == null) {
			instance = new LazySingleton();
		}
		return instance;
	}
}

publci class LazySingleton {
	private static LazySingleton instance = null;
	private LazySingleton() {
	
	}
	public static LazySingleton getInstance() {
		if (instance == null) {
			instance = LazySingleton.buildInstance();
		}
		return instance;
	}
	private static synchronized LazySingleton buildInstance() {
		if (instance == null) {
			instance = new LazySingleton();
		}
		
		return instance;
	}
}

package structure;
import java.util.ArrayList;
import java.util.List;
interface Item {
  void print();
  String getName();
  void setName(String name);
  List<Item> getChilds();
  int addChild(Item item);
}
abstract class Component implements Item {
  private List<Item> childs = new ArrayList<>();
  private String name;
  @Override
  public String getName() {
    return name;
  }
  @Override
  public void setName(String name) {
    this.name = name;
  }
  @Override
  public List<Item> getChilds() {
    return childs;
  }
  @Override
  public void print() {
    String className = this.getClass().getSimpleName();
    System.out.println("print " + className + "(" + getName() + ")");
    List<Item> childs = getChilds();
    for (Item item: childs) {
      item.print();
    }
  }
  @Override
  public int addChild(Item item) {
    List<Item> childs = getChilds();
    if (childs == null) {
      return 0;
    }
    if (item != null) {
      childs.add(item);
    }
    return childs.size();
  }
}
class WinForm extends Component { }
class Button extends Component { }
class CheckBox extends Component { }
class Frame extends Component { }
class Label extends Component { }
class LinkLabel extends Component { }
class PasswordBox extends Component { }
class Picture extends Component { }
class TextBox extends Component { }
public class Composition {
  public static void main(String[] args) throws IllegalAccessException, InstantiationException {
    Item mainForm = createChild("WINDOW窗口", WinForm.class);
    addChilds(mainForm);
    mainForm.print();
  }
  static <T> Item createChild(String name, Class<T> clazz) throws IllegalAccessException, InstantiationException {
    Item child = (Item)clazz.newInstance();
    child.setName(name);
    return child;
  }
  static void addChilds(Item mainForm) throws InstantiationException, IllegalAccessException {
    mainForm.addChild(createChild("LOGO图片", Picture.class));
    mainForm.addChild(createChild("登录", Button.class));
    mainForm.addChild(createChild("注册", Button.class));
    Item frame = createChild("FRAME1", Frame.class);
    mainForm.addChild(frame);
    frame.addChild(createChild("用户名", Label.class));
    frame.addChild(createChild("文本框", TextBox.class));
    frame.addChild(createChild("密码", Label.class));
    frame.addChild(createChild("密码框", PasswordBox.class));
    frame.addChild(createChild("复选框", CheckBox.class));
    frame.addChild(createChild("记住用户名", TextBox.class));
    frame.addChild(createChild("忘记密码", LinkLabel.class));
  }
}

print WinForm(WINDOW窗口)
print Picture(LOGO图片)
print Button(登录)
print Button(注册)
print Frame(FRAME1)
print Label(用户名)
print TextBox(文本框)
print Label(密码)
print PasswordBox(密码框)
print CheckBox(复选框)
print TextBox(记住用户名)
print LinkLabel(忘记密码)