转载：http://www.iteye.com/topic/420224

作者：mfcai

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在j2me联网时，在eclipse控制台下有一个警告：“若要避免潜在的死锁，应该在commandAction()处理程序之外的其他线程中执行可能 会阻塞的，操作（如网络连接）。
为了避免潜在的死锁，我们经常把把联网的代码部分写到一个线程中去执行。
而实际应用中，网络连接的事务也都是使用一个单独的线程进行的。

线程的创建可以使用Runnable接口来实现，也可以使用Thread类实现，还可以以匿名内部类的方式创建。在本文中，分别用这三种方式给出 了j2me联网的例子。
代码均测试通过。可以直接使用。
1.通过继承Thread类创建

/** 
 * 测试Thread类线程 
 * @author mfcai 
 */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class OpenConn implements Runnable {
	private HttpURLConnection conn;
	private URL url;

	// Thread thread1;

	public OpenConn(String url) throws MalformedURLException {
		this.url = new URL(url);
	}

	public void run() {
		try {
			conn = (HttpURLConnection) url.openConnection();
		} catch (IOException e) {
			e.printStackTrace();
			url = null;
		}
	}

	public HttpURLConnection getConn() {
		return conn;
	}

	public static void main(String[] args) throws Exception {
		// 创建Runnable类
		OpenConn openConn = new OpenConn("http://www.google.com");
		// 创建线程
		Thread thread = new Thread(openConn);
		// openConn.thread1=thread;
		thread.start();
		thread.join(10000);// wait 10 seconds
		HttpURLConnection c = openConn.getConn();
		if (c != null) {
			System.out.println("连接网络成功...");
			BufferedReader r = new BufferedReader(new InputStreamReader(c.getInputStream()));
			String s = r.readLine();
			while (s != null) {
				System.out.println(s);
				s = r.readLine();
			}
		} else {
			System.out.println("超时错误,连接网络失败...");
		}
	}
}

? 2.通过引用Runnable接口创建

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/** 
* 测试Runnable接口线程 
* @author mfcai 
*/ 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class OpenConn2 extends Thread {
	private HttpURLConnection conn;
	private URL url;

	public OpenConn2(String url) throws MalformedURLException {
		this.url = new URL(url);
	}

	public void run() {
		try {
			conn = (HttpURLConnection) url.openConnection();
		} catch (IOException e) {
			e.printStackTrace();
			url = null;
		}
	}

	public HttpURLConnection getConn() {
		return conn;
	}

	public static void main(String[] args) throws Exception {
		OpenConn2 openConn = new OpenConn2("http://www.google.com");
		openConn.start();
		openConn.join(10000);// wait 10 seconds
		HttpURLConnection c = openConn.getConn();
		if (c != null) {
			System.out.println("连接网络成功...");
			BufferedReader r = new BufferedReader(new InputStreamReader(c.getInputStream()));
			String s = r.readLine();
			while (s != null) {
				System.out.println(s);
				s = r.readLine();
			}
		} else {
			System.out.println("超时错误,连接网络失败...");
		}
	}
}

? 3.以匿名内部类的方式创建
即在一个方法中创建线程，当方法被调用时，线程即启动，如下：

/** 
* 测试匿名线程线程创建 
* @author mfcai 
*/ 


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class OpenConn3 {
	private HttpURLConnection conn;
	private URL url;
	
	public static void main(String[] args){
		try{
			OpenConn3 open3= new OpenConn3();
			open3.strartMyThread();
		}catch(Exception ex){
			System.out.println(ex.toString());
		}
	}
	 public void strartMyThread() throws Exception{ 
		 this.url =new URL("http://www.google.com");
         java.lang.Runnable runner=new Runnable(){
        	 public void run(){ 
        		 try {
        				conn = (HttpURLConnection) url.openConnection();
        			} catch (IOException e) {
        				e.printStackTrace();
        				url = null;
        			}
        	 }

         };
         Thread openConn=new Thread(runner); 
         openConn.start(); 
         openConn.join(10000);// wait 10 seconds

 		if (conn != null) {
 			System.out.println("连接网络成功...");
 			BufferedReader r = new BufferedReader(new InputStreamReader(conn
 					.getInputStream()));
 			String s = r.readLine();
 			while (s != null) {
 				System.out.println(s);
 				s = r.readLine();
 			}
 		} else {
 			System.out.println("超时错误,连接网络失败...");
 		}

	 }
}

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