Java结构型设计模式之享元模式示例详解

public interface ITicket {
    /**
     * 查询票信息
     */
    void query();
}

public class TrainTicket implements ITicket {
    /**
     * 出发地
     */
    private String from;
    /**
     * 目的地
     */
    private String to;
    /**
     * 票种类
     */
    private String type;
    /**
     * 票价
     */
    private int price;
    public TrainTicket(String from, String to, String type) {
        this.from = from;
        this.to = to;
        this.type = type;
    }
    public void query() {
        this.price = new Random().nextInt(100);
        int num = new Random().nextInt(10);
        System.out.println(String.format("从%s到%s,%s,票价：%s元,剩余车票：%s", this.from, this.to, this.type, this.price, num));
    }
}

public class TicketFactory {
    private static Map<String, ITicket> ticketPool = new ConcurrentHashMap<String, ITicket>();
    public static ITicket queryTicket(String from, String to, String type) {
        String key = "出发站：" from   " 目的站："   to   " 坐席类型："   type;
        if (TicketFactory.ticketPool.containsKey(key)) {
            System.out.println("使用缓存查询："   key);
            return TicketFactory.ticketPool.get(key);
        }
        System.out.println("第一次查询，创建对象: "   key);
        ITicket ticket = new TrainTicket(from, to, type);
        TicketFactory.ticketPool.put(key, ticket);
        return ticket;
    }
}

    public static void main(String[] args) {
        ITicket ticket = TicketFactory.queryTicket("A", "B", "特等座");
        ticket.query();
        ticket = TicketFactory.queryTicket("A", "B","一等座");
        ticket.query();
        ticket = TicketFactory.queryTicket("A", "B","特等座");
        ticket.query();
    }

@Data
public class ConnectionPool {
    private Vector<Connection> pool;
    private String url = "jdbc:mysql://localhost:3306/demo";
    private String username = "root";
    private String password = "123456";
    private String driverClassName = "com.mysql.jdbc.Driver";
    private int poolSize = 100;
    /**
     * 初始化一定数量的连接
     */
    public ConnectionPool() {
        pool = new Vector<Connection>(poolSize);
        try {
            Class.forName(driverClassName);
            for (int i = 0; i < poolSize; i  ) {
                Connection conn = DriverManager.getConnection(url, username, password);
                pool.add(conn);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 获取连接
     * @return
     */
    public synchronized Connection getConnection() {
        if (pool.size() > 0) {
            Connection conn = pool.get(0);
            pool.remove(conn);
            return conn;
        }
        return null;
    }
    /**
     * 释放归还连接
     * @param conn
     */
    public synchronized void release(Connection conn) {
        pool.add(conn);
    }
}

    public static void main(String[] args) {
        ConnectionPool connectionPool = new ConnectionPool();
        Connection conn = connectionPool.getConnection();
        System.out.println("获取一个连接："   conn   "连接池中剩余："   connectionPool.getPool().size());
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            connectionPool.release(conn);
            System.out.println("归还连接池，连接池总数： "   connectionPool.getPool().size());
        }
    }