Java でのバイト バッファ クラスのデモ

java.lang.Object> java.nio.Buffer>java.nio.ByteBuffer`

package bytebuffer.delftstack.com.util;
/*We will demonstrate the byte buffer class in this program.
 *First of all, we will create a byte buffer and its object and allocate it a size.
 *Then, we will convert the int data type to the byte by typecasting with the help of PuntInt()
 *function */
import java.nio.*;
import java.util.*;
// main class
public class Example1 {
  // main function
  public static void main(String[] args) {
    // capacity declaration
    int allocCapac = 6;
    // Creating the ByteBuffer
    try {
      // creating object of ByteBuffer
      // and allocating size capacity
      ByteBuffer createOBJ = ByteBuffer.allocate(allocCapac);
      // putting the int to byte typecast value
      // in ByteBuffer using putInt() method
      createOBJ.put((byte) 20);
      createOBJ.put((byte) 40);
      createOBJ.put((byte) 60);
      createOBJ.put((byte) 80);
      createOBJ.put((byte) 100);
      createOBJ.put((byte) 120);
      createOBJ.rewind();
      // We will print the byter buffer now
      System.out.println("The byte buffer: " + Arrays.toString(createOBJ.array()));
    }
    // catch exception for error
    catch (IllegalArgumentException e) {
      System.out.println("IllegalArgumentException catched");
    } catch (ReadOnlyBufferException e) {
      System.out.println("ReadOnlyBufferException catched");
    }
  }
}
// class

The byte buffer: [20, 40, 60, 80, 100, 120]

package bytebuffer.delftstack.com.util;

/*In this code block, we will use string instead of int like the previous program.
First of all, we declare the capacity of the byte buffer to `100`.
Then, we create its object, put the string instead of the int value, and allocate it with size.
After that, we will use `rewind()` to rewind this buffer and in the while loop and finally apply the
getChar function. Please check out the following code block to learn more:*/

import java.nio.ByteBuffer;
public class Example2 {
  public static void main(String[] args) {
    // Declaring the capacity of the ByteBuffer
    int capacity = 100;
    // Creating the ByteBuffer
    // creating object of ByteBuffer
    // and allocating size capacity
    ByteBuffer bufferOBJ = ByteBuffer.allocate(capacity);
    // putting the string in the bytebuffer
    bufferOBJ.asCharBuffer().put("JAVA");
    // rewind the Bytebuffer
    bufferOBJ.rewind(); // The position is set to zero and the mark isdiscarded.
    // Declaring the variable
    char charr;
    // print the ByteBuffer
    System.out.println("This is the default byte buffer: ");
    while ((charr = bufferOBJ.getChar()) != 0) System.out.print(charr + "");
    // rewind the Bytebuffer
    bufferOBJ.rewind();
    // Reads the char at this buffer's current position
    // using getChar() method
    char FrstVal = bufferOBJ.getChar();
    // print the char FrstVal
    System.out.println("\n\n The first byte value is : " + FrstVal);
    // Reads the char at this buffer's next position
    // using getChar() method
    char NXTval = bufferOBJ.getChar();
    // print the char FrstVal
    System.out.print("The next byte value is : " + NXTval);
  }
}

This is the default byte buffer:
JAVA
The first byte value is : J
The next byte value is : A