我編程網絡單獨的類,它需要在一個線程中運行,到目前爲止,還沒有問題,但是我不能讓它黯然工作。java的單網絡實現Runnable
網絡類:
public class Network extends Thread {
private static Network cachedInstance = new Network();
private PrintWriter out;
private BufferedReader in;
private Network() {
}
private void init() {
try {
Socket clientSocket = new Socket(Config.HOST_NAME, Config.HOST_PORT);
out = new PrintWriter(clientSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String fromServer;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
}
} catch (IOException ex) {
Logger.getLogger(Controller.class.getName()).log(Level.SEVERE, null, ex);
}
}
public static Network getInstance() {
return cachedInstance;
}
public void send(final String string) {
out.println(string);
}
@Override
public void run() {
init();
}
}
控制器類的一部分:
public void clientTest() {
int random = new Random().nextInt(1000);
Network.getInstance().start();
Network.getInstance().send(random + "");
}
我得到的錯誤:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at network.Network.send(Network.java:52)
at controller.Controller.clientTest(Controller.java:126)
所以它看起來像單一網絡實例不正確實例化,理論上應該是不可能的。
第二個問題我有是,如果我能避免使用這樣的:
Network.getInstance().start();
換句話說,我想,以確保只有一個線程(網絡類)創建,它總是被默認運行當這些類被初始化時。目前這種方式並不差,但我認爲它會更好。
對於人們想知道爲什麼我用這個方法:基本上,我只是想用Network.send()發送到一個固定的服務器。那個服務器當然可以發回東西,但是在那之後,網絡需要在某個時刻從Controller響應和調用方法。
問候。
編輯:建議的解決方案,基於反應
Network.class:
public class Network implements Runnable {
private static final Network cachedInstance;
static {
Network tempInstance = null;
try {
tempInstance = new Network(Config.HOST_NAME, Config.HOST_PORT);
} catch (IOException ex) {
Logger.getLogger(Network.class.getName()).log(Level.SEVERE, null, ex);
} finally {
cachedInstance = tempInstance;
}
}
private final Socket clientSocket;
private final PrintWriter out;
private final BufferedReader in;
private Network(final String hostname, final int port) throws IOException {
clientSocket = new Socket(hostname, port);
out = new PrintWriter(clientSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
}
public static Network getInstance() {
return cachedInstance;
}
@Override
public void run() {
try {
String fromServer;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
}
} catch (IOException ex) {
Logger.getLogger(Network.class.getName()).log(Level.SEVERE, null, ex);
}
}
public void send(final String string) {
out.println(string);
}
public void close() {
try {
in.close();
out.close();
clientSocket.close();
} catch (IOException ex) {
Logger.getLogger(Network.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
調用代碼:
public void clientTest() {
int random = new Random().nextInt(1000);
Network network = Network.getInstance();
new Thread(network).start();
network.send(random + "");
network.close();
}
這只是用於測試,在現實中的連接需求在用戶關閉程序之前保持打開狀態。
您正在設置「out」之前調用send。順便說一句你需要將字段'out'設置爲'volatile'字段,否則你可能永遠不會看到它被設置。 – 2013-04-26 22:00:00