使用线程创建的三种方法实现j2me联网（PS：我想做android！NND！）

本文链接：https://blog.youkuaiyun.com/zcljy0318/article/details/5980045

本文介绍了如何在J2ME环境中避免死锁，并提供了三种不同方式的联网代码示例：通过继承Thread类创建线程、使用Runnable接口创建线程以及利用匿名内部类创建线程。

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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

Java代码

/**
* 测试Thread类线程
* @author mfcai
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
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..." );
}
}
}

/** 
* 测试Thread类线程 
* @author mfcai 
*/ 
  import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
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

Java代码

/**
* 测试Runnable接口线程
* @author mfcai
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
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..." );
}
}
}

/** 
* 测试Runnable接口线程 
* @author mfcai 
*/ 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
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：

Java代码