Java implementation of a journal (tasks journalization)

Journal.java

package fr.free.nrw.journal;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.PrintWriter;

import org.apache.log4j.Logger;

/**
 * Journal that keeps track of what tasks have been done, and which ones are still to do.
 * Records tasks that have been been performed, so that they are not performed again if the program must be relaunched, for instance due to a crash.
 * 
 * The tasks must always be the same, and occur in the same order. If tasks change, you must delete the journal file before running the app again.
 * 
 * Terminology:
 * - Task: Something to do. Each task is written as an item to the journal.
 * - Previous run: The previous time the app was run. The journal matches tasks of the previous and current runs. 
 */
public class Journal {

	/**
	 * State
	 * 0: Reading from last run's journal
	 * 1: Adding to the journal
	 */
	private enum State {
		READING,
		WRITING
	}
	private State state = State.READING;
	
	final static Logger log = Logger.getLogger(Journal.class);
	
	private String journalFile;
	
	PrintWriter journalWriter;
	
	BufferedReader journalReader;
	
	public Journal(String journalFile) {
		this.journalFile = journalFile;
		
		try {
			journalReader = new BufferedReader(new FileReader(journalFile));
		}
		catch(Exception e) {
			log.info("Journal file does not exist, creating a new one.");
			switchToWritingState();
		}
	}
	
	private void switchToWritingState() {
		state = State.WRITING;
		
		try {
			FileWriter fw = new FileWriter(journalFile, true);
		    BufferedWriter bw = new BufferedWriter(fw);
		    journalWriter = new PrintWriter(bw);
		}
		catch(Exception e) {
			log.error("Journal error: Opening " + journalFile + " for writing failed.", e);
		}
	}
	
	public void markAsDone(String task) {
		if (state == State.WRITING) {
			journalWriter.println(task);
			journalWriter.flush(); // Otherwise the line is not always written, even in cases where no error happen.
		}
		else {
			log.error("Journal error: Tried to write task \"" + task + "\" to journal before reaching end of last time's journal. If data has changed, you must delete last time's journal.");
		}
	}
	
	public boolean isDoneAlready(String task) {
		if (state == State.READING) {
			String lastRunTask = null;
			try {
				lastRunTask = journalReader.readLine();
			} catch (Exception e) {
				log.error("Journal error: Could not read journal when trying to match current task: " + task, e);
				e.printStackTrace();
				return false;
			} // Task of the previous run.
			if(lastRunTask == null) {
				// End of the journal file reached.
				switchToWritingState();
				return false;
			}
			if (lastRunTask.equals(task)) {
				return true;
			}
			else {
				log.error("Journal error: Task \"" + task + "\" does not match task in journal: " + lastRunTask);
				return false;
			}
		}
		else {
			return false; // We are in writing mode, which means there are only new tasks from now on.
		}
	}
}