Java: Write HashMap into File

Question

I'm working on a program that saves two words into a HashMap. I need to be able to take the HashMap key and value and write it into a file as "key:value" format. When my save() method is called, the HashMap contents are supposed to be written into the file whose name was given as parameter to the constructor. The method returns false if the file can't be saved; otherwise it returns true. However, its not working if the File does not exist. It's also not saving changes made to an existing file. I'm not understanding how to read/write files too well... Thank you.

package dictionary;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.util.HashMap;
import java.util.Scanner;


public class MindfulDictionary {

private HashMap<String, String> words;
private File file;

public MindfulDictionary() {
    this.words = new HashMap<String, String>();
}

public MindfulDictionary(String file) {
    this.file = new File(file);
    this.words = new HashMap<String, String>();
}

public boolean load() {
    try {
        Scanner fileReader = new Scanner(this.file);
        while (fileReader.hasNextLine()) {
            String line = fileReader.nextLine();
            String[] parts = line.split(":");   // the line is split at :

            String word = parts[0];
            String trans = parts[1];
            this.add(word, trans);
        }
    } catch (Exception e) {
        System.out.println("nope");
    }
    return true;
}

public boolean save() {
    boolean saved = true;
    BufferedWriter writer = null;
    try {
        writer = new BufferedWriter(new FileWriter(this.file.getName(), true));
        for (String key : this.words.keySet()) {
            writer.write(key + ":" + this.words.get(key) + "\n");
            writer.newLine();
            writer.flush();
            writer.close();
        }
    } catch (Exception e) {

    }
    return saved;
}

public void add(String word, String translation) {
    if ((!this.words.containsKey(word))) {
        this.words.put(word, translation);
    }
}

public String translate(String word) {
    if (this.words.containsKey(word)) {
        return this.words.get(word);
    } else if (this.words.containsValue(word)) {
        for (String key : this.words.keySet()) {
            if (this.words.get(key).equals(word)) {
                return key;
            }
        }
    }
    return null;
}

public void remove(String word) {
    if (this.words.containsKey(word)) {
        this.words.remove(word);
    } else if (this.words.containsValue(word)) {
        String remove = "";
        for (String key : this.words.keySet()) {
            if (this.words.get(key).equals(word)) {
                remove += key;
            }
        }
        this.words.remove(remove);
    }
}

}

Answer 1

Notice this part of your code,

try {
    writer = new BufferedWriter(new FileWriter(this.file.getName(), true));
    for (String key : this.words.keySet()) {
        writer.write(key + ":" + this.words.get(key) + "\n");
        writer.newLine();
        writer.flush();
        writer.close(); // !!
    }
} catch (Exception e) {

}

Here, you are calling close() on the BufferedWriter object. You can not use the object after you have called close() on it.

Once the stream has been closed, further write() or flush() invocations will cause an IOException to be thrown.

Read more about close() here.

Also, since you are catching all the exceptions and not doing anything with them, you did not notice the IOException . In future NEVER do this. At the least log any exception that occurs. This will help you with your debugging.