Read file with SeekableByteChannel - Java File Path IO

Java examples for File Path IO:File Channel

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Description

Read file with SeekableByteChannel

Demo Code

import java.io.*;
import java.nio.*;
import java.nio.file.*;
import java.nio.channels.*;

public class FindInt {
    private Path file;

    FindInt(Path file) {// w  w  w .  j  av  a 2 s. c  o m
        this.file = file;
    }

    public int seek() throws IOException {
        int num = -1;

        try (SeekableByteChannel fc = Files.newByteChannel(file)) {

            ByteBuffer buf = ByteBuffer.allocate(8);

            //Get the offset into the file.
            fc.read(buf);
            long offset = buf.getLong(0);

            //Seek to the offset location.
            fc.position(offset);
            buf.rewind();

            //Read the 'secret' value.
            fc.read(buf);
            num = buf.getInt(0);
        } catch (IOException x) {
            System.err.println(x);
        }
        return num;
    }

    public static void main(String[] args) throws IOException {
        Path file = Paths.get("datafile");
        int num = new FindInt(file).seek();
        System.out.println("The value is " + num);
    }
}

/*
 * Copyright (c) 2009, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

Result


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