package com.madhubanti.singleprocess.player.interaction.main;
import com.madhubanti.singleprocess.player.interaction.initiation.Initiator;
import com.madhubanti.singleprocess.player.interaction.receiver.Receiver;
/**
* Starts application, Instantiate Players and help in garbage collection
*
*/
public class MainApp {
/**
* main method instantiates Initiator and Receiver and helps in message
* communication between them
*
* Also sets unused objects to null and callss System.exit
*
* @param args
* String array
*/
public static void main(String[] args) {
// Instantiates Initiator
Initiator initiatorPlayer = new Initiator();
// Instantiates Receiver
Receiver receiverPlayer = new Receiver();
// start sending message
initiatorPlayer.sendMessage(receiverPlayer);
// sets the value of the unused instances to null for garbage collection
initiatorPlayer = null;
receiverPlayer = null;
System.exit(0);
}
}
package com.madhubanti.singleprocess.player.interaction;
import com.madhubanti.singleprocess.player.interaction.initiation.Initiator;
/**
* Parent class of {@link Initiator} and {@link Receiver}
*
* @author Madhubanti Jash
*
*/
public class Player {
/**
* returns counter value in string
*
* @param counter
* 1,2,3 etc
* @return String format of counter
*/
public String checkCounter(int counter) {
switch (counter) {
case 1:
return "first";
case 2:
return "second";
case 3:
return "third";
case 4:
return "fourth";
case 5:
return "fifth";
case 6:
return "sixth";
case 7:
return "seventh";
case 8:
return "eighth";
case 9:
return "ninth";
case 10:
return "tenth";
default:
return "garbage collection";
}
}
}
package com.madhubanti.singleprocess.player.interaction.initiation;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.madhubanti.singleprocess.player.interaction.Player;
import com.madhubanti.singleprocess.player.interaction.log.ConfigLogger;
import com.madhubanti.singleprocess.player.interaction.receiver.Receiver;
/**
* Initiates message communication with {@link Receiver} and receives new
* message from it.
*
* @author Madhubanti Jash
*
*/
public class Initiator extends Player {
/** initializes logger */
private static final Logger LOGGER = Logger.getLogger(Initiator.class.getName());
/**
* sends message to Receiver and receives new message in return
*
* @param receiverPlayer
* instance of Receiver
*
*/
public void sendMessage(Receiver receiverPlayer) {
ConfigLogger.addLoggerHandler(LOGGER);
String message = "";
String prefix = "Sent message for ";
String postfix = " Time";
for (int counter = 1; counter <= 10; counter++) {
message = prefix + super.checkCounter(counter) + postfix;
LOGGER.log(Level.FINER, "message to be sent is: {0}", message);
String newReceivedMessage = receiverPlayer.receiveMessage(message, counter);
LOGGER.log(Level.FINER, "Received new message from Receiver is: {0}", newReceivedMessage);
}
}
}
package com.madhubanti.singleprocess.player.interaction.receiver;
import com.madhubanti.singleprocess.player.interaction.Player;
import com.madhubanti.singleprocess.player.interaction.initiation.Initiator;
/**
* Receives message communication from {@link Initiator} and sends back new
* message
*
* @author Madhubanti Jash
*
*/
public class Receiver extends Player {
/**
* receives message from initiator and sends back new message in return
*
* @param message
* received message
* @return newMessage new message to Initiator
*
*/
public String receiveMessage(String message, int counter) {
String messageForNullValue = "have not received message; so not returning new message.";
String postfix = " time from Receiver class.";
String receivedMessage = message;
String prefix = "Received message for ";
String checkCounter = checkCounter(counter);
String counterString = " The counter is: ";
String newMessage = receivedMessage == null ? messageForNullValue
: prefix + checkCounter + postfix + counterString + counter;
return newMessage;
}
}
package com.madhubanti.singleprocess.player.interaction.log;
import java.util.logging.ConsoleHandler;
import java.util.logging.Level;
import java.util.logging.Logger;
/** responsible to add log level and handler */
public class ConfigLogger extends Logger {
/**
* parameterized constructor
*
* @param name
* A name for the logger
* @param resourceBundleName
* name of resource bundle
*
*/
protected ConfigLogger(String name, String resourceBundleName) {
super(name, resourceBundleName);
}
/**
* add log level and handler
*
* @param logger
* LOGGER
*/
public static void addLoggerHandler(Logger logger) {
ConsoleHandler consoleHandler = new ConsoleHandler();
logger.addHandler(consoleHandler);
consoleHandler.setLevel(Level.ALL);
logger.setLevel(Level.ALL);
}
}
我上面提到了5个班级。这里Initiator启动与Receiver的通信。响应那个Receiver发回消息。 发送和接收消息10次后，我想优雅地完成不需要的对象。
为此，我在完成工作后将initiatorPlayer和receiverPlayer的值设置为null，然后在MainApp.java中调用System.exit(0)。这是实现“优雅地完成”的正确方法吗？
答案 0 :(得分：3)
优雅地结束意味着通常以可以调用拆卸/取消设置操作的方式完成最终确定 为此，您必须确保应用程序无法通过崩溃终止。
完成宽限期不需要
不需要将变量设置为null，因为在JVM终止时将删除所有Java对象。所以你应该删除这些语句。
除了调用System.exit(0);之外，您将通过让main()线程完成执行来获得相同的结果。
优雅结束的例子
假设在您的代码中，Receiver在引擎盖下创建了一个未附加到JVM的资源，例如用于接收消息的网络套接字。
当程序终止时，您希望不再需要所有不再需要的资源：正在运行的JVM分配的对象以及打开的套接字。
JVM出口不必关闭连接到套接字的所有资源。调用receiverPlayer.dipose()可能是实现这一目标的方法。
但要做到这一点，你需要让程序优雅地完成。
例如：
public static void main(String[] args) {
Receiver receiverPlayer = null;
try{
// Instantiates Initiator
Initiator initiatorPlayer = new Initiator();
// Instantiates Receiver
receiverPlayer = new Receiver();
// start sending message
initiatorPlayer.sendMessage(receiverPlayer);
}
finally{
if (receiverPlayer != null){
receiverPlayer.dispose();
}
}
}