Android File Path Get getRoot(File file)

Description

Returns the filesystem root for file.

License

Open Source License

Exception

Parameter	Description
IllegalArgumentException	if file is null, or non-existent
SecurityException	if a security manager exists and denies read access to file
IOException	if an I/O problem occurs

Declaration

public static File getRoot(File file) throws IllegalArgumentException,
        SecurityException, IOException 

Method Source Code

/*/*  w  w w . j  ava2 s  . c om*/
Copyright ? 2008 Brent Boyer

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the Lesser GNU General Public License for more details.

You should have received a copy of the Lesser GNU General Public License along with this program (see the license directory in this project).  If not, see <http://www.gnu.org/licenses/>.
 */

import bb.science.FormatUtil;
import bb.util.Check;
import bb.util.StringUtil;
import bb.util.ThrowableUtil;
import bb.util.logging.LogUtil;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.util.Random;
import java.util.logging.Level;
import org.junit.Assert;
import org.junit.Test;

public class Main{
    /**
     * Returns the filesystem root for file.
     * Specifically, this method traces back parent Files until there are no more, and returns the last one found.
     * <p>
     * <i>Note: unlike almost all other methods in this class, file need not be a normal file;</i>
     * it could be a directory as well.
     * Corollary: the result is file itself if file is a filesystem root.
     * <p>
     * @throws IllegalArgumentException if file is null, or non-existent
     * @throws SecurityException if a security manager exists and denies read access to file
     * @throws IOException if an I/O problem occurs
     */
    public static File getRoot(File file) throws IllegalArgumentException,
            SecurityException, IOException {
        Check.arg().notNull(file);
        if (!file.exists())
            throw new IllegalArgumentException("file = " + file.getPath()
                    + " is a non-existent path");

        file = file.getCanonicalFile(); // CRITICAL: if file is a relative path like ./ then the getParentFile call below will return null prematurely; cure this by putting file into canonical form
        for (File parent = file.getParentFile(); parent != null; parent = file
                .getParentFile()) {
            file = parent;
        }
        return file; // file is now the last non-null File in the chain explored by the loop above
    }
}

Related

1. getCanonicalFile(File file)
2. getDrive(File file)
3. getPathLastIndex(String fileName)
4. getPathLastIndex(String fileName, int fromIndex)