Java by API/java.io/InputStream

extends InputStream

  
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
public class Main {
  public static void main(String[] argv) throws Exception {
    ByteBuffer buf = ByteBuffer.allocate(10);
    OutputStream os = new ByteBufferBackedOutputStream(buf);
    InputStream is = new  ByteBufferBackedInputStream(buf);
  }
}
class ByteBufferBackedInputStream extends InputStream{
  
  ByteBuffer buf;
  ByteBufferBackedInputStream( ByteBuffer buf){
    this.buf = buf;
  }
  public synchronized int read() throws IOException {
    if (!buf.hasRemaining()) {
      return -1;
    }
    return buf.get();
  }
  public synchronized int read(byte[] bytes, int off, int len) throws IOException {
    len = Math.min(len, buf.remaining());
    buf.get(bytes, off, len);
    return len;
  }
}
class ByteBufferBackedOutputStream extends OutputStream{
  ByteBuffer buf;
  ByteBufferBackedOutputStream( ByteBuffer buf){
    this.buf = buf;
  }
  public synchronized void write(int b) throws IOException {
    buf.put((byte) b);
  }
  public synchronized void write(byte[] bytes, int off, int len) throws IOException {
    buf.put(bytes, off, len);
  }
  
}

InputStream: read(byte[] b)

   
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class Main {
  public static void main(String[] args) {
    try {
      copy(System.in, System.out);
    } catch (IOException ex) {
      System.err.println(ex);
    }
  }
  public static void copy(InputStream in, OutputStream out) throws IOException {
    byte[] buffer = new byte[1024];
    while (true) {
      int bytesRead = in.read(buffer);
      if (bytesRead == -1)
        break;
      out.write(buffer, 0, bytesRead);
    }
  }
}

InputStream: read(byte[] b, int off, int len)

  

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
public class Main {
  public static void main(String[] argv) throws Exception {
    File file = new File("c:\\a.bat");
    InputStream is = new FileInputStream(file);
    long length = file.length();
    if (length > Integer.MAX_VALUE) {
      System.out.println("File is too large");
    }
    byte[] bytes = new byte[(int) length];
    int offset = 0;
    int numRead = 0;
    while (numRead >= 0) {
      numRead = is.read(bytes, offset, bytes.length - offset);
      offset += numRead;
    }
    if (offset < bytes.length) {
      throw new IOException("Could not completely read file " + file.getName());
    }
    is.close();
    System.out.println(new String(bytes));
  }
}