Java by API/java.nio/ByteBuffer

Содержание

1 ByteBuffer: allocateDirect(int size)
2 ByteBuffer: allocate(int capacity)
3 ByteBuffer: asCharBuffer()
4 ByteBuffer: asDoubleBuffer()
5 ByteBuffer: asFloatBuffer()
6 ByteBuffer: asLongBuffer()
7 ByteBuffer: asShortBuffer()
8 ByteBuffer: capacity()
9 ByteBuffer: clear()
10 ByteBuffer: compact()
11 ByteBuffer: flip()
12 ByteBuffer: get()
13 ByteBuffer: get(byte[] dst, int offset, int length)
14 ByteBuffer: getChar()
15 ByteBuffer: getDouble()
16 ByteBuffer: getFloat()
17 ByteBuffer: getInt()
18 ByteBuffer: get(int index)
19 ByteBuffer: getLong()
20 ByteBuffer: isDirect()
21 ByteBuffer: limit()
22 ByteBuffer: order()
23 ByteBuffer: order(ByteOrder bo)
24 ByteBuffer: position()
25 ByteBuffer: position(int newPosition)
26 ByteBuffer: put(byte b)
27 ByteBuffer: putChar(char ch)
28 ByteBuffer: putDouble(double value)
29 ByteBuffer: putFloat(float value)
30 ByteBuffer: putInt(int i)
31 ByteBuffer: putLong(long value)
32 ByteBuffer: putShort(int index, short value)
33 ByteBuffer: putShort(short value)
34 ByteBuffer: rewind()
35 ByteBuffer: wrap(byte[] array)

ByteBuffer: allocateDirect(int size)

   
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String args[]) {
    FileOutputStream fileOutputStream;
    FileChannel fileChannel;
    ByteBuffer byteBuffer;
    try {
      fileOutputStream = new FileOutputStream("test.txt");
      fileChannel = fileOutputStream.getChannel();
      byteBuffer = ByteBuffer.allocateDirect(26);
      for (int i = 0; i < 26; i++)
        byteBuffer.put((byte) ("A" + i));
      byteBuffer.rewind();
      fileChannel.write(byteBuffer);
      fileChannel.close();
      fileOutputStream.close();
    } catch (IOException exc) {
      System.out.println(exc);
    }
  }
}

ByteBuffer: allocate(int capacity)

   
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String args[]) {
    FileInputStream fIn;
    FileChannel fChan;
    long fSize;
    ByteBuffer mBuf;
    try {
      fIn = new FileInputStream("test.txt");
      fChan = fIn.getChannel();
      fSize = fChan.size();
      mBuf = ByteBuffer.allocate((int) fSize);
      fChan.read(mBuf);
      mBuf.rewind();
      for (int i = 0; i < fSize; i++)
        System.out.print((char) mBuf.get());
      fChan.close();
      fIn.close();
    } catch (IOException exc) {
      System.out.println(exc);
    }
  }
}

ByteBuffer: asCharBuffer()

   
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
public class MainClass {
  public static void main(String[] args) {
    File aFile = new File("afile.txt");
    FileOutputStream outputFile = null;
    try {
      outputFile = new FileOutputStream(aFile, true);
      System.out.println("File stream created successfully.");
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    }
    ByteBuffer buf = ByteBuffer.allocate(1024);
    System.out.println("\nByte buffer:");
    System.out.printf("position = %2d  Limit = %4d  capacity = %4d%n", buf.position(), buf.limit(),
        buf.capacity());
    // Create a view buffer
    CharBuffer charBuf = buf.asCharBuffer();
    System.out.println("Char view buffer:");
    System.out.printf("position = %2d  Limit = %4d  capacity = %4d%n", charBuf.position(), charBuf
        .limit(), charBuf.capacity());
    try {
      outputFile.close(); // Close the O/P stream & the channel
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}

ByteBuffer: asDoubleBuffer()

  
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;
public class Main {
  public static void main(String[] args) {
    ByteBuffer bb = ByteBuffer.wrap(new byte[] { 0, 0, 0, 0, 0, 0, 0, "a" });
    bb.rewind();
    System.out.println("Byte Buffer");
    while (bb.hasRemaining())
      System.out.println(bb.position() + " -> " + bb.get());
    CharBuffer cb = ((ByteBuffer) bb.rewind()).asCharBuffer();
    System.out.println("Char Buffer");
    while (cb.hasRemaining())
      System.out.println(cb.position() + " -> " + cb.get());
    FloatBuffer fb = ((ByteBuffer) bb.rewind()).asFloatBuffer();
    System.out.println("Float Buffer");
    while (fb.hasRemaining())
      System.out.println(fb.position() + " -> " + fb.get());
    IntBuffer ib = ((ByteBuffer) bb.rewind()).asIntBuffer();
    System.out.println("Int Buffer");
    while (ib.hasRemaining())
      System.out.println(ib.position() + " -> " + ib.get());
    LongBuffer lb = ((ByteBuffer) bb.rewind()).asLongBuffer();
    System.out.println("Long Buffer");
    while (lb.hasRemaining())
      System.out.println(lb.position() + " -> " + lb.get());
    ShortBuffer sb = ((ByteBuffer) bb.rewind()).asShortBuffer();
    System.out.println("Short Buffer");
    while (sb.hasRemaining())
      System.out.println(sb.position() + " -> " + sb.get());
    DoubleBuffer db = ((ByteBuffer) bb.rewind()).asDoubleBuffer();
    System.out.println("Double Buffer");
    while (db.hasRemaining())
      System.out.println(db.position() + " -> " + db.get());
  }
}

ByteBuffer: asFloatBuffer()

  
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;
public class Main {
  public static void main(String[] args) {
    ByteBuffer bb = ByteBuffer.wrap(new byte[] { 0, 0, 0, 0, 0, 0, 0, "a" });
    bb.rewind();
    System.out.println("Byte Buffer");
    while (bb.hasRemaining())
      System.out.println(bb.position() + " -> " + bb.get());
    CharBuffer cb = ((ByteBuffer) bb.rewind()).asCharBuffer();
    System.out.println("Char Buffer");
    while (cb.hasRemaining())
      System.out.println(cb.position() + " -> " + cb.get());
    FloatBuffer fb = ((ByteBuffer) bb.rewind()).asFloatBuffer();
    System.out.println("Float Buffer");
    while (fb.hasRemaining())
      System.out.println(fb.position() + " -> " + fb.get());
    IntBuffer ib = ((ByteBuffer) bb.rewind()).asIntBuffer();
    System.out.println("Int Buffer");
    while (ib.hasRemaining())
      System.out.println(ib.position() + " -> " + ib.get());
    LongBuffer lb = ((ByteBuffer) bb.rewind()).asLongBuffer();
    System.out.println("Long Buffer");
    while (lb.hasRemaining())
      System.out.println(lb.position() + " -> " + lb.get());
    ShortBuffer sb = ((ByteBuffer) bb.rewind()).asShortBuffer();
    System.out.println("Short Buffer");
    while (sb.hasRemaining())
      System.out.println(sb.position() + " -> " + sb.get());
    DoubleBuffer db = ((ByteBuffer) bb.rewind()).asDoubleBuffer();
    System.out.println("Double Buffer");
    while (db.hasRemaining())
      System.out.println(db.position() + " -> " + db.get());
  }
}

ByteBuffer: asLongBuffer()

   
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    File aFile = new File("file.dat");
    FileInputStream inFile = null;
    try {
      inFile = new FileInputStream(aFile);
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
      System.exit(0);
    }
    FileChannel inChannel = inFile.getChannel();
    final int COUNT = 6;
    ByteBuffer buf = ByteBuffer.allocate(8 * COUNT);
    long[] data = new long[COUNT];
    try {
      while (inChannel.read(buf) != -1) {
        ((ByteBuffer) (buf.flip())).asLongBuffer().get(data);
        System.out.println();
        for (long prime : data)
          System.out.printf("%10d", prime);
        buf.clear();
      }
      System.out.println("\nEOF reached.");
      inFile.close();
    } catch (IOException e) {
      e.printStackTrace(System.err);
      System.exit(1);
    }
  }
}

ByteBuffer: asShortBuffer()

  
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;
public class Main {
  public static void main(String[] args) {
    ByteBuffer bb = ByteBuffer.wrap(new byte[] { 0, 0, 0, 0, 0, 0, 0, "a" });
    bb.rewind();
    System.out.println("Byte Buffer");
    while (bb.hasRemaining())
      System.out.println(bb.position() + " -> " + bb.get());
    CharBuffer cb = ((ByteBuffer) bb.rewind()).asCharBuffer();
    System.out.println("Char Buffer");
    while (cb.hasRemaining())
      System.out.println(cb.position() + " -> " + cb.get());
    FloatBuffer fb = ((ByteBuffer) bb.rewind()).asFloatBuffer();
    System.out.println("Float Buffer");
    while (fb.hasRemaining())
      System.out.println(fb.position() + " -> " + fb.get());
    IntBuffer ib = ((ByteBuffer) bb.rewind()).asIntBuffer();
    System.out.println("Int Buffer");
    while (ib.hasRemaining())
      System.out.println(ib.position() + " -> " + ib.get());
    LongBuffer lb = ((ByteBuffer) bb.rewind()).asLongBuffer();
    System.out.println("Long Buffer");
    while (lb.hasRemaining())
      System.out.println(lb.position() + " -> " + lb.get());
    ShortBuffer sb = ((ByteBuffer) bb.rewind()).asShortBuffer();
    System.out.println("Short Buffer");
    while (sb.hasRemaining())
      System.out.println(sb.position() + " -> " + sb.get());
    DoubleBuffer db = ((ByteBuffer) bb.rewind()).asDoubleBuffer();
    System.out.println("Double Buffer");
    while (db.hasRemaining())
      System.out.println(db.position() + " -> " + db.get());
  }
}

ByteBuffer: capacity()

   
/*
 * Output:
File stream created successfully.
New buffer:           position = 0  Limit = 1024  capacity = 1024
Buffer after loading: position = 30  Limit = 1024  capacity = 1024
Buffer after flip:    position = 0  Limit = 30  capacity = 1024
Buffer contents written to file.
 */
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    String phrase = new String("www.jexp.ru\n");
    File aFile = new File("test.txt");   
    FileOutputStream outputFile = null;  
    try {
      outputFile = new FileOutputStream(aFile, true);
      System.out.println("File stream created successfully.");
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    } 
    FileChannel outChannel = outputFile.getChannel();
    
    ByteBuffer buf = ByteBuffer.allocate(1024);
    System.out.println("New buffer:           position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    // Load the data into the buffer
    for (char ch : phrase.toCharArray()) {
      buf.putChar(ch);
    }
    System.out.println("Buffer after loading: position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    buf.flip();
    System.out.println("Buffer after flip:    position = " + buf.position() 
                       + "\tLimit = " + buf.limit() + "\tcapacity = " 
                       + buf.capacity());
    try {
      outChannel.write(buf);
      outputFile.close();
      System.out.println("Buffer contents written to file.");
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}

ByteBuffer: clear()

   
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) throws Exception {
    String fromFileName = args[0];
    String toFileName = args[1];
    FileChannel in = new FileInputStream(fromFileName).getChannel();
    FileChannel out = new FileOutputStream(toFileName).getChannel();
    ByteBuffer buff = ByteBuffer.allocate(32 * 1024);
    while (in.read(buff) > 0) {
      buff.flip();
      out.write(buff);
      buff.clear();
    }
    in.close();
    out.close();
  }
}

ByteBuffer: compact()

   
import java.io.File;
import java.io.FileInputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class Main {
  public static void main(String[] args) throws Exception{
    File aFile = new File("primes.txt");
    FileInputStream inFile = new FileInputStream(aFile);
    FileChannel inChannel = inFile.getChannel();
    ByteBuffer buf = ByteBuffer.allocateDirect(1024);
    buf.position(buf.limit());
    while (true) {
      if (buf.remaining() < 8) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      int strLength = (int) buf.getDouble();
      if (buf.remaining() < 2 * strLength) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      byte[] strChars = new byte[2 * strLength];
      buf.get(strChars);
      if (buf.remaining() < 8) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      System.out.println(strLength);
      System.out.println(ByteBuffer.wrap(strChars).asCharBuffer());
      System.out.println(buf.getLong());
    }
    inFile.close();  }
}

ByteBuffer: flip()

   
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) throws Exception {
    String fromFileName = args[0];
    String toFileName = args[1];
    FileChannel in = new FileInputStream(fromFileName).getChannel();
    FileChannel out = new FileOutputStream(toFileName).getChannel();
    ByteBuffer buff = ByteBuffer.allocate(32 * 1024);
    while (in.read(buff) > 0) {
      buff.flip();
      out.write(buff);
      buff.clear();
    }
    in.close();
    out.close();
  }
}

ByteBuffer: get()

   
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String args[]) {
    FileInputStream fIn;
    FileChannel fChan;
    long fSize;
    ByteBuffer mBuf;
    try {
      fIn = new FileInputStream("test.txt");
      fChan = fIn.getChannel();
      fSize = fChan.size();
      mBuf = ByteBuffer.allocate((int) fSize);
      fChan.read(mBuf);
      mBuf.rewind();
      for (int i = 0; i < fSize; i++)
        System.out.print((char) mBuf.get());
      fChan.close();
      fIn.close();
    } catch (IOException exc) {
      System.out.println(exc);
    }
  }
}

ByteBuffer: get(byte[] dst, int offset, int length)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    byte[] bytes = new byte[10];
    ByteBuffer buf = ByteBuffer.wrap(bytes);
    buf.clear();
    bytes = new byte[buf.capacity()];
    buf.get(bytes, 0, bytes.length);
  }
}

ByteBuffer: getChar()

  
import java.nio.ByteBuffer;
public class Main {
  private static final int BSIZE = 1024;
  public static void main(String[] args) {
    ByteBuffer bb = ByteBuffer.allocate(BSIZE);
    bb.asCharBuffer().put("Howdy!");
    char c;
    while ((c = bb.getChar()) != 0)
      System.out.print(c + " ");
    System.out.println();
  }
}

ByteBuffer: getDouble()

   
import java.io.File;
import java.io.FileInputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class Main {
  public static void main(String[] args) throws Exception{
    File aFile = new File("primes.txt");
    FileInputStream inFile = new FileInputStream(aFile);
    FileChannel inChannel = inFile.getChannel();
    ByteBuffer buf = ByteBuffer.allocateDirect(1024);
    buf.position(buf.limit());
    while (true) {
      if (buf.remaining() < 8) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      int strLength = (int) buf.getDouble();
      if (buf.remaining() < 2 * strLength) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      byte[] strChars = new byte[2 * strLength];
      buf.get(strChars);
      if (buf.remaining() < 8) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      System.out.println(strLength);
      System.out.println(ByteBuffer.wrap(strChars).asCharBuffer());
      System.out.println(buf.getLong());
    }
    inFile.close();  }
}

ByteBuffer: getFloat()

 

import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    // Put values of different types
    buf.putFloat(12.3F);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    float f = buf.getFloat();
  }
}

ByteBuffer: getInt()

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    // Put values of different types
    buf.putInt(123);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    int i = buf.getInt();
  }
}

ByteBuffer: get(int index)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocateDirect(10);
    byte b = buf.get(5); // position=0
  }
}

ByteBuffer: getLong()

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    // Put values of different types
    buf.putLong(123L);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    long l = buf.getLong();
  }
}

ByteBuffer: isDirect()

 
//Contents in a non-direct ByteBuffer are stored in the normal memory. 
//Contents in a direct ByteBuffer are stored in some I/O device.
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer bbuf = ByteBuffer.wrap(new byte[10]);
    boolean isDirect = bbuf.isDirect(); // false
    bbuf = ByteBuffer.allocate(10);
    isDirect = bbuf.isDirect(); // false
    bbuf = ByteBuffer.allocateDirect(10);
    isDirect = bbuf.isDirect(); // true
  }
}

ByteBuffer: limit()

   
/*
 * Output:
File stream created successfully.
New buffer:           position = 0  Limit = 1024  capacity = 1024
Buffer after loading: position = 30  Limit = 1024  capacity = 1024
Buffer after flip:    position = 0  Limit = 30  capacity = 1024
Buffer contents written to file.
 */
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    String phrase = new String("www.jexp.ru\n");
    File aFile = new File("test.txt");   
    FileOutputStream outputFile = null;  
    try {
      outputFile = new FileOutputStream(aFile, true);
      System.out.println("File stream created successfully.");
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    } 
    FileChannel outChannel = outputFile.getChannel();
    
    ByteBuffer buf = ByteBuffer.allocate(1024);
    System.out.println("New buffer:           position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    // Load the data into the buffer
    for (char ch : phrase.toCharArray()) {
      buf.putChar(ch);
    }
    System.out.println("Buffer after loading: position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    buf.flip();
    System.out.println("Buffer after flip:    position = " + buf.position() 
                       + "\tLimit = " + buf.limit() + "\tcapacity = " 
                       + buf.capacity());
    try {
      outChannel.write(buf);
      outputFile.close();
      System.out.println("Buffer contents written to file.");
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}

ByteBuffer: order()

 
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(10);
    
    ByteOrder order = buf.order(); // ByteOrder.BIG_ENDIAN
  }
}

ByteBuffer: order(ByteOrder bo)

 
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
/**
 * Test asCharBuffer view.
 */
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer byteBuffer = ByteBuffer.allocate(7).order(ByteOrder.BIG_ENDIAN);
    CharBuffer charBuffer = byteBuffer.asCharBuffer();
    byteBuffer.put(0, (byte) 0);
    byteBuffer.put(1, (byte) "H");
    byteBuffer.put(2, (byte) 0);
    byteBuffer.put(3, (byte) "i");
    byteBuffer.put(4, (byte) 0);
    byteBuffer.put(5, (byte) "!");
    byteBuffer.put(6, (byte) 0);
    println(byteBuffer);
    println(charBuffer);
    // now slice it differently
    byteBuffer.position(4);
    charBuffer = byteBuffer.asCharBuffer();
    println(byteBuffer);
    println(charBuffer);
  }
  // Print info about a buffer
  private static void println(Buffer buffer) {
    System.out.println("pos=" + buffer.position() + ", limit=" + buffer.limit() + ", capacity="
        + buffer.capacity() + ": "" + buffer.toString() + """);
  }
}

ByteBuffer: position()

   
/*
 * Output:
File stream created successfully.
New buffer:           position = 0  Limit = 1024  capacity = 1024
Buffer after loading: position = 30  Limit = 1024  capacity = 1024
Buffer after flip:    position = 0  Limit = 30  capacity = 1024
Buffer contents written to file.
 */
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    String phrase = new String("www.jexp.ru\n");
    File aFile = new File("test.txt");   
    FileOutputStream outputFile = null;  
    try {
      outputFile = new FileOutputStream(aFile, true);
      System.out.println("File stream created successfully.");
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    } 
    FileChannel outChannel = outputFile.getChannel();
    
    ByteBuffer buf = ByteBuffer.allocate(1024);
    System.out.println("New buffer:           position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    // Load the data into the buffer
    for (char ch : phrase.toCharArray()) {
      buf.putChar(ch);
    }
    System.out.println("Buffer after loading: position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    buf.flip();
    System.out.println("Buffer after flip:    position = " + buf.position() 
                       + "\tLimit = " + buf.limit() + "\tcapacity = " 
                       + buf.capacity());
    try {
      outChannel.write(buf);
      outputFile.close();
      System.out.println("Buffer contents written to file.");
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}

ByteBuffer: position(int newPosition)

 
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
/**
 * Test asCharBuffer view.
 */
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer byteBuffer = ByteBuffer.allocate(7).order(ByteOrder.BIG_ENDIAN);
    CharBuffer charBuffer = byteBuffer.asCharBuffer();
    byteBuffer.put(0, (byte) 0);
    byteBuffer.put(1, (byte) "H");
    byteBuffer.put(2, (byte) 0);
    byteBuffer.put(3, (byte) "i");
    byteBuffer.put(4, (byte) 0);
    byteBuffer.put(5, (byte) "!");
    byteBuffer.put(6, (byte) 0);
    println(byteBuffer);
    println(charBuffer);
    // now slice it differently
    byteBuffer.position(4);
    charBuffer = byteBuffer.asCharBuffer();
    println(byteBuffer);
    println(charBuffer);
  }
  // Print info about a buffer
  private static void println(Buffer buffer) {
    System.out.println("pos=" + buffer.position() + ", limit=" + buffer.limit() + ", capacity="
        + buffer.capacity() + ": "" + buffer.toString() + """);
  }
}

ByteBuffer: put(byte b)

   
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String args[]) {
    FileOutputStream fileOutputStream;
    FileChannel fileChannel;
    ByteBuffer byteBuffer;
    try {
      fileOutputStream = new FileOutputStream("test.txt");
      fileChannel = fileOutputStream.getChannel();
      byteBuffer = ByteBuffer.allocateDirect(26);
      for (int i = 0; i < 26; i++)
        byteBuffer.put((byte) ("A" + i));
      byteBuffer.rewind();
      fileChannel.write(byteBuffer);
      fileChannel.close();
      fileOutputStream.close();
    } catch (IOException exc) {
      System.out.println(exc);
    }
  }
}

ByteBuffer: putChar(char ch)

   
/*
 * Output:
File stream created successfully.
New buffer:           position = 0  Limit = 1024  capacity = 1024
Buffer after loading: position = 30  Limit = 1024  capacity = 1024
Buffer after flip:    position = 0  Limit = 30  capacity = 1024
Buffer contents written to file.
 */
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    String phrase = new String("www.jexp.ru\n");
    File aFile = new File("test.txt");   
    FileOutputStream outputFile = null;  
    try {
      outputFile = new FileOutputStream(aFile, true);
      System.out.println("File stream created successfully.");
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    } 
    FileChannel outChannel = outputFile.getChannel();
    
    ByteBuffer buf = ByteBuffer.allocate(1024);
    System.out.println("New buffer:           position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    // Load the data into the buffer
    for (char ch : phrase.toCharArray()) {
      buf.putChar(ch);
    }
    System.out.println("Buffer after loading: position = " + buf.position()
                       + "\tLimit = " + buf.limit() + "\tcapacity = "
                       + buf.capacity());
    buf.flip();
    System.out.println("Buffer after flip:    position = " + buf.position() 
                       + "\tLimit = " + buf.limit() + "\tcapacity = " 
                       + buf.capacity());
    try {
      outChannel.write(buf);
      outputFile.close();
      System.out.println("Buffer contents written to file.");
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}

ByteBuffer: putDouble(double value)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    // Put values of different types
    buf.putDouble(12.3D);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    double d = buf.getDouble();
  }
}

ByteBuffer: putFloat(float value)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    // Put values of different types
    buf.putFloat(12.3F);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    float f = buf.getFloat();
  }
}

ByteBuffer: putInt(int i)

   
/*
 * Output:
 
 */
import java.io.File;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    try {
      File aFile = new File("test.txt");
      FileOutputStream outputFile = null;
      outputFile = new FileOutputStream(aFile, true);
      FileChannel outChannel = outputFile.getChannel();
      ByteBuffer buf = ByteBuffer.allocate(200);
      buf.putInt(10).asCharBuffer().put("www.jexp.ru");
      buf.position(10).flip();
      outChannel.write(buf);
      buf.clear();
      outputFile.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

ByteBuffer: putLong(long value)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    // Put values of different types
    buf.putLong(123L);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    long l = buf.getLong();
  }
}

ByteBuffer: putShort(int index, short value)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(10);
    buf.putShort(0, (short) 123);
    buf.get(0); // 0
    buf.get(1); // 123
  }
}

ByteBuffer: putShort(short value)

 
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(100);
    buf.putShort((short) 123);
    // Reset position for reading
    buf.flip();
    // Retrieve the values
    short s = buf.getShort();
  }
}

ByteBuffer: rewind()

   
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String args[]) {
    FileInputStream fIn;
    FileChannel fChan;
    long fSize;
    ByteBuffer mBuf;
    try {
      fIn = new FileInputStream("test.txt");
      fChan = fIn.getChannel();
      fSize = fChan.size();
      mBuf = ByteBuffer.allocate((int) fSize);
      fChan.read(mBuf);
      mBuf.rewind();
      for (int i = 0; i < fSize; i++)
        System.out.print((char) mBuf.get());
      fChan.close();
      fIn.close();
    } catch (IOException exc) {
      System.out.println(exc);
    }
  }
}

ByteBuffer: wrap(byte[] array)

   
import java.io.File;
import java.io.FileInputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class Main {
  public static void main(String[] args) throws Exception{
    File aFile = new File("primes.txt");
    FileInputStream inFile = new FileInputStream(aFile);
    FileChannel inChannel = inFile.getChannel();
    ByteBuffer buf = ByteBuffer.allocateDirect(1024);
    buf.position(buf.limit());
    while (true) {
      if (buf.remaining() < 8) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      int strLength = (int) buf.getDouble();
      if (buf.remaining() < 2 * strLength) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      byte[] strChars = new byte[2 * strLength];
      buf.get(strChars);
      if (buf.remaining() < 8) {
        if (inChannel.read(buf.rupact()) == -1) {
          break;
        }
        buf.flip();
      }
      System.out.println(strLength);
      System.out.println(ByteBuffer.wrap(strChars).asCharBuffer());
      System.out.println(buf.getLong());
    }
    inFile.close();  }
}

Java by API/java.nio/ByteBuffer

Содержание

ByteBuffer: allocateDirect(int size)

ByteBuffer: allocate(int capacity)

ByteBuffer: asCharBuffer()

ByteBuffer: asDoubleBuffer()

ByteBuffer: asFloatBuffer()

ByteBuffer: asLongBuffer()

ByteBuffer: asShortBuffer()

ByteBuffer: capacity()

ByteBuffer: clear()

ByteBuffer: compact()

ByteBuffer: flip()

ByteBuffer: get()

ByteBuffer: get(byte[] dst, int offset, int length)

ByteBuffer: getChar()

ByteBuffer: getDouble()

ByteBuffer: getFloat()

ByteBuffer: getInt()

ByteBuffer: get(int index)

ByteBuffer: getLong()

ByteBuffer: isDirect()

ByteBuffer: limit()

ByteBuffer: order()

ByteBuffer: order(ByteOrder bo)

ByteBuffer: position()

ByteBuffer: position(int newPosition)

ByteBuffer: put(byte b)

ByteBuffer: putChar(char ch)

ByteBuffer: putDouble(double value)

ByteBuffer: putFloat(float value)

ByteBuffer: putInt(int i)

ByteBuffer: putLong(long value)

ByteBuffer: putShort(int index, short value)

ByteBuffer: putShort(short value)

ByteBuffer: rewind()

ByteBuffer: wrap(byte[] array)

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