JavaIoFileAdapter.java

package com.github.drapostolos.rdp4j;

import java.io.File;
import java.io.IOException;
import java.util.LinkedHashSet;
import java.util.Set;

import com.github.drapostolos.rdp4j.spi.FileElement;
import com.github.drapostolos.rdp4j.spi.PolledDirectory;

/**
 * An adapter for java's {@link File} class, that enables monitoring a directory
 * on the local file system. The main purpose of this adapter is to provide
 * an example how to use an Abstract Directory Poller.
 * <p>
 * Using this to listen to events on your local file system is discouraged, use the 
 * Java7 WatchService functionality instead. For Java6 see other options
 * <a href=http://www.rgagnon.com/javadetails/java-0617.html>here</a>.
 *
 * @see <a href="https://github.com/drapostolos/rdp4j/wiki/User-Guide">User-Guide</a>
 */
public final class JavaIoFileAdapter implements FileElement, PolledDirectory {

    private final File file;

    /**
     * @param file the directory to monitor for changes.
     */
    public JavaIoFileAdapter(File file) {
        if (file == null) {
            throw new NullPointerException("null argument not allowed!");
        }
        this.file = file;
    }

    /**
     * @return the {@link File} object wrapped by this adapter object.
     */
    public File getFile() {
        return file;
    }

    /**
     * @see File#lastModified()
     */
    @Override
    public long lastModified() throws IOException {
        long lastModified = file.lastModified();
        if (lastModified == 0L) {
            String message = "Unknown I/O error occured when retriveing lastModified " +
                    "attribute for file '%s'.";
            throw new IOException(String.format(message, file));
        }
        return lastModified;
    }

    /**
     * @see File#isDirectory()
     */
    @Override
    public boolean isDirectory() {
        return file.isDirectory();
    }

    /**
     * @see File#getName()
     */
    @Override
    public String getName() {
        return file.getName();
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((file == null) ? 0 : file.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        JavaIoFileAdapter other = (JavaIoFileAdapter) obj;
        if (file == null) {
            if (other.file != null)
                return false;
        } else if (!file.equals(other.file))
            return false;
        return true;
    }

    @Override
    public Set<FileElement> listFiles() throws IOException {
        Set<FileElement> result = new LinkedHashSet<FileElement>();
        File[] files = file.listFiles();
        if (files == null) {
            String message = "Unknown I/O error when listing files in directory '%s'.";
            throw new IOException(String.format(message, file));
        }
        for (File child : file.listFiles()) {
            result.add(new JavaIoFileAdapter(child));
        }
        return result;
    }

    /**
     * @see File#toString()
     */
    @Override
    public String toString() {
        return file.toString();
    }

}