android-platform-libcore/luni/src/main/java/java/io/FileReader.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.io;

/**
 * A specialized {@link Reader} that reads from a file in the file system.
 * All read requests made by calling methods in this class are directly
 * forwarded to the equivalent function of the underlying operating system.
 * Since this may induce some performance penalty, in particular if many small
 * read requests are made, a FileReader is often wrapped by a
 * BufferedReader.
 *
 * @see BufferedReader
 * @see FileWriter
 */
public class FileReader extends InputStreamReader {

    /**
     * Constructs a new FileReader on the given {@code file}.
     *
     * @param file
     *            a File to be opened for reading characters from.
     * @throws FileNotFoundException
     *             if {@code file} does not exist.
     */
    public FileReader(File file) throws FileNotFoundException {
        super(new FileInputStream(file));
    }

    /**
     * Construct a new FileReader on the given FileDescriptor {@code fd}. Since
     * a previously opened FileDescriptor is passed as an argument, no
     * FileNotFoundException can be thrown.
     *
     * @param fd
     *            the previously opened file descriptor.
     */
    public FileReader(FileDescriptor fd) {
        super(new FileInputStream(fd));
    }

    /**
     * Construct a new FileReader on the given file named {@code filename}.
     *
     * @param filename
     *            an absolute or relative path specifying the file to open.
     * @throws FileNotFoundException
     *             if there is no file named {@code filename}.
     */
    public FileReader(String filename) throws FileNotFoundException {
        super(new FileInputStream(filename));
    }
}