Java: file write on finalize method
- by sowrov
In my understanding a singleton object will destroy only when the application is about to terminate. So in C++ I write a Singleton class to log my application and in that Singleton logger's destructor I log the time when my application was terminated. Things worked perfectly in C++.
Now I want to have that same logger in Java, as in java there is no destructor so I implemented the finalize method for that singleton logger. But it seem that finalize method actually never get called.
So, I add that System.runFinalizersOnExit(true); line, somewhere in my code (though I know it is deprecated) and that finalize method get called every time before termination of the app. But still there is a problem! If I try to write anything on file in that finalize method, It does not work, though System.out work without any problem! :(
Can you guys help me on this problem? Here is a sample code of what I am try to do:
Singleton Logger Class:
public class MyLogger {
FileWriter writer;
private MyLogger() {
try {
this.writer = new FileWriter("log.txt");
}
catch (IOException ex) {
}
}
public static MyLogger getInstance() {
return MyLoggerHolder.INSTANCE;
}
private static class MyLoggerHolder {
private static final MyLogger INSTANCE = new MyLogger();
}
@Override
protected void finalize () {
try {
super.finalize();
System.out.println("Here"); //worked correctly.
this.writer.write(new Date().toString()+System.getProperty("line.separator"));
this.writer.write("End");
this.writer.flush(); //does not work!
this.writer.close();
}
catch (Throwable ex) {
}
}
public synchronized void log(String str) {
try {
this.writer.write(new Date().toString()+System.getProperty("line.separator"));
this.writer.write(str+"\n");
this.writer.flush();
}
catch (IOException ex) {
}
}
}
Main:
public class Main {
public static void main(String[] args) {
System.runFinalizersOnExit(true);
MyLogger logger = MyLogger.getInstance();
logger.log("test");
}
}
