Scala example source code file (FileHistory.java)

This example Scala source code file (FileHistory.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

bufferedreader, entry, failed, file, filehistory, ioexception, loading, printstream, purging, string

The FileHistory.java Scala example source code

/*
 * Copyright (c) 2002-2007, Marc Prud'hommeaux. All rights reserved.
 *
 * This software is distributable under the BSD license. See the terms of the
 * BSD license in the documentation provided with this software.
 */

package scala.tools.jline.console.history;

import scala.tools.jline.internal.Log;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.Flushable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.Reader;
import java.util.ListIterator;

/**
 * {@link History} using a file for persistent backing.
 * <p/>
 * Implementers should install shutdown hook to call {@link FileHistory#flush}
 * to save history to disk.
 *
 * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
 * @since 2.0
 */
public class FileHistory
    extends MemoryHistory
    implements PersistentHistory, Flushable
{
    private final File file;

    public FileHistory(final File file) throws IOException {
        assert file != null;
        this.file = file;
        load(file);
    }

    public File getFile() {
        return file;
    }

    public void load(final File file) throws IOException {
        assert file != null;
        if (file.exists()) {
            Log.trace("Loading history from: ", file);
            load(new FileReader(file));
        }
    }

    public void load(final InputStream input) throws IOException {
        assert input != null;
        load(new InputStreamReader(input));
    }

    public void load(final Reader reader) throws IOException {
        assert reader != null;
        BufferedReader input = new BufferedReader(reader);

        String item;
        while ((item = input.readLine()) != null) {
            add(item);
        }
    }

    public void flush() throws IOException {
        Log.trace("Flushing history");

        if (!file.exists()) {
            File dir = file.getParentFile();
            if (!dir.exists() && !dir.mkdirs()) {
                Log.warn("Failed to create directory: ", dir);
            }
            if (!file.createNewFile()) {
                Log.warn("Failed to create file: ", file);
            }
        }

        PrintStream out = new PrintStream(new BufferedOutputStream(new FileOutputStream(file)));
        try {
            for (Entry entry : this) {
                out.println(entry.value());
            }
        }
        finally {
            out.close();
        }
    }

    public void purge() throws IOException {
        Log.trace("Purging history");

        clear();

        if (!file.delete()) {
            Log.warn("Failed to delete history file: ", file);
        }
    }
}