23种设计模式

http://blog.youkuaiyun.com/zhangerqing/article/details/8194653

创建对象：

1，单例(Singleton)

作用：系统中只有一个该类的实例。

public class LazySingleton {
	private static LazySingleton singleton = null;// 不再做实例化操作
	private LazySingleton(){};// 构造方法声明为私有，这样就保证了只能有一个对象存在
	// 提供一个外部得到类的方法
	public synchronized static LazySingleton getInstance() {
		if (null == singleton) {
			synchronized (LazySingleton.class) {
				if (null == singleton) {
					singleton = new LazySingleton();
				}
			}
		}
		return singleton;
	}
}

2，工厂

作用：将实例化交给一个工厂类来管理。如果你现在想增加一个功能：发及时信息，则只需做一个实现类，实现Sender接口，同时做一个工厂类，实现Provider接口，就OK了，无需去改动现成的代码。这样做，拓展性较好

 

public interface Sender {
	public void Send();
}

public class MailSender implements Sender {
	@Override
	public void Send() {
		System.out.println("this is mailsender!");
	}
}

public class SmsSender implements Sender {

	@Override
	public void Send() {
		System.out.println("this is sms sender!");
	}
}

 

public interface Provider {
	public Sender produce();
}

public class SendMailFactory implements Provider {
	@Override
	public Sender produce(){
		return new MailSender();
	}
}

public class SendSmsFactory implements Provider{
	@Override
	public Sender produce() {
		return new SmsSender();
	}
}

public class Test {
	public static void main(String[] args) {
		Provider provider = new SendMailFactory();
		Sender sender = provider.produce();
		sender.Send();
	}
}

3，构造者

作用：将实例化交给一个建造者来管理。

 

public class User{
	private String name;
	private int age;
	private boolean sex;
	public static class Builder {
		private String name;
		private int age;
		private boolean sex;
		public Builder name(String val) {
			name = val;
			return this;
		}
		
		public Builder age(int val) {
			age = val;
			return this;
		}
		
		public Builder sex(boolean val) {
			sex = val;
			return this;
		}
		
		public User build() {
			return new User(this);
		}
	}
	
	private User(Builder builder)  {
		name = builder.name;
		age = builder.age;
		sex = builder.sex;
	}
}

User user = new User.Builder.name("hello").age(18).sex(true).build();

 

4，原型(Prototype)

作用，将实例化通过clone()方法，即内存拷贝的方式，以此减少创建相似对象的消耗。

 

public class User {
	private String name;
	/* 浅复制 */
	public Object clone() throws CloneNotSupportedException {
		User user = (User) super.clone();
		return user;
	}
	/* 深复制 */
	public Object deepClone() throws IOException, ClassNotFoundException {
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		ObjectOutputStream oos = new ObjectOutputStream(bos);
		oos.writeObject(this);
		ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
		ObjectInputStream ois = new ObjectInputStream(bis);
		return ois.readObject();
	}<span style="font-family: Arial, Helvetica, sans-serif;">}</span>

程序结构：

1，适配器

作用：