单例模式

----------------------------------------单例模式(饿汉,懒汉)

 

//单例
public class TestSingle {

	private static TestSingle instance=new TestSingle();//饿汉模式
	//1.构造方法私有化
	private TestSingle(){
		
	}
	//2.提供一个方法获得该对象的实例（懒汉模式）
	public  static synchronized TestSingle getInstance(){
//		if(instance==null){
//			instance=new TestSingle();
//		}
		return instance;
	}
}

 

 

 

------------------------------------属性文件的读取

 

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Properties;

public class TestPropertes {
	 public static void main(String[] args) {
		Properties pro=new Properties();
	
		InputStream is=null;
		OutputStream out=null;
		try {
			is=new FileInputStream("db.properties");
			pro.load(is);
			pro.setProperty("driver", "1234567");
			out=new FileOutputStream("db.properties");
			pro.store(out,"aaaaaa");
			
			System.out.println(pro.get("hello"));
		} catch (FileNotFoundException e) {
		
			e.printStackTrace();
		} catch (IOException e) {
		
			e.printStackTrace();
		}finally{
			try {
				out.close();
				is.close();
			} catch (IOException e) {
				
				e.printStackTrace();
			}
			
		}
	}
}

 

  

---------------------------------------属性文件配合单例模式的应用

 

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
 * 将读属性设计成单例模式
 * @author Administrator
 *
 */
public class Env extends Properties {
	private static Env instance;

	private Env() {
		//创建一输入流,该路径文件必须在src目录下的文件才有效
		InputStream is = this.getClass().getResourceAsStream(
				"/resource/db.properties");
		try {
			//加载文件中的数据到内存中(到properties对象中)
			this.load(is);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	public static synchronized Env getInstance() {
		if (instance == null) {
			instance = new Env();
		}
		return instance;
	}
}

 

   如果不导入import架包

   则在获取时应该写Env.getInstance().getProperty("driver");

   这样子可以增加代码的可读性,可以避免阅读代码者看作是本类得方法属性.

 

//静态导入
import static util.Env.getInstance;
public class BaseManagerDAO {
	
	private static final String DRIVER =getInstance().getProperty("driver");
	private static final String URL = getInstance().getProperty("url");
	private static final String UNAME = getInstance().getProperty("uname");
	private static final String UPASS = getInstance().getProperty("upass");
	public Connection con=null;
	public void getCon(){
		try {
			Class.forName(DRIVER);
			con=DriverManager.getConnection(URL,UNAME,UPASS);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	    
	}

 属性文件属于键值映射的文件

 在该示例中,属性文件内容为

 #aaaaaa
 #Tue Jul 12 15:20:53 CST 2011
 url=jdbc:oracle:thin:@localhost:1521:ORCL
 driver=oracle.jdbc.driver.OracleDriver
 uname=accp
 upass=accp