内部类

匿名内部类，比如下面函数内部initialize定义了两个匿名类（红色代码部分）：

publicsynchronizedvoid initialize(Environment env,

Detector detector,

DaemonListener listener,

PlainLogger[] loggers) throws NullPointerException,

IllegalStateException {

if (fInitialized) {

return;

}

Helper.notNull( env, "environment" );

Helper.notNull( detector, "detector" );

fDetector = detector;

fDaemonListener = listener;

// Check the loggers.

if (loggers != null) {

for (int i = 0; i < loggers.length; i++) {

if (loggers[i] != null && !loggers[i].isLoggable( )) {

thrownew IllegalStateException( "Logger" + i

+ " isn't loggable" );

}

}

// Get loggers.

if (loggers.length >= 1) {

fAppLogger = loggers[0];

}

if (loggers.length >= 2) {

fErrorLogger = loggers[1];

}

}

// Initialize the daemon options first.

initDaemonOptions( env );

// Check the loggers.

if (loggers != null) {

for (int i = 0; i < loggers.length; i++) {

if (loggers[i] != null && !loggers[i].isLoggable( )) {

thrownew IllegalStateException( "Logger" + i

+ " isn't loggable" );

}

}

// Get loggers.

if (loggers.length >= 1) {

fAppLogger = loggers[0];

}

if (loggers.length >= 2) {

fErrorLogger = loggers[1];

}

}

log( "Using Rv Daemon: " + fDaemonOptions.getCurTransportOption( ) );

// Implements a detector listener.

DetectorListener detectorListener = new DetectorListener( ) {

public void onConnected() {

String newDaemon = fDaemonOptions.getCurTransportOption( );

log( "Connected to Daemon: " + newDaemon );

synchronized (Daemon.this) {

fState = DaemonState.CONNECTED;

for (Iterator i = fSwitchHandlers.iterator( ); i.hasNext( );) {

((SwitchHandler) i.next( )).doSwitching( newDaemon );

}

fState = DaemonState.SWITCHED;

}

log( "Switched to Daemon: " + newDaemon );

if (fDaemonListener != null) {

fDaemonListener.onStateChanged( fState,

fLastDaemon,

newDaemon );

}

}

public void onDisconnected() {

synchronized (Daemon.this) {

fState = DaemonState.SWITCHING;

round( );

}

log( "Disconnected to Daemon: " + fLastDaemon );

if (fDaemonListener != null) {

fDaemonListener.onStateChanged( fState,

fLastDaemon,

fDaemonOptions.peekNextAvailTransportOption( ) );

}

detect( );

}

};

fDetector.registerDetectorListener( detectorListener );

// Do the first connecting in other thread.

Thread first = new Thread( "InitialDetector" ) {

public void run() {

detect( );

}

};

first.start( );

fInitialized = true;

log( "Daemon detecting initialized." );

}

new DetectorListener( ){...}等价于创建一个派生自接口DectorListener的子类，然后返回该类的引用。 同样的道理，另外一个是从Thread派生并且重写了run函数，因此该类可以作为一个县城对象运行。