Java中的缓冲区 rewind() 方法及示例
Java.nio.ByteBuffer 类的rewind()方法用于回绕这个缓冲区。位置设置为零并且标记被丢弃。在一系列通道写入或获取操作之前调用此方法,假设已经适当地设置了限制。调用此方法既不会更改也不会丢弃标记的值。
句法:
public ByteBuffer rewind()
返回值:此方法返回此缓冲区。
以下是说明 rewind() 方法的示例:
示例 1:
// Java program to demonstrate
// rewind() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// defining and allocating ByteBuffer
// using allocate() method
ByteBuffer byteBuffer
= ByteBuffer.allocate(4);
// put byte value in byteBuffer
// using put() method
byteBuffer.put((byte)20);
byteBuffer.put((byte)'a');
// Typecast Bytebuffer to buffer
Buffer buffer = (Buffer)byteBuffer;
// print the byte buffer
System.out.println("Buffer before operation: "
+ Arrays.toString(
(byte[])buffer.array())
+ "\nPosition: "
+ buffer.position()
+ "\nLimit: "
+ buffer.limit());
// rewind the Buffer
// using rewind() method
buffer.rewind();
// print the bytebuffer
System.out.println("\nBuffer after operation: "
+ Arrays.toString(
(byte[])buffer.array())
+ "\nPosition: "
+ buffer.position()
+ "\nLimit: "
+ buffer.limit());
}
}
输出:
Buffer before operation: [20, 97, 0, 0]
Position: 2
Limit: 4
Buffer after operation: [20, 97, 0, 0]
Position: 0
Limit: 4
示例 2:
// Java program to demonstrate
// rewind() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// defining and allocating ByteBuffer
// using allocate() method
ByteBuffer byteBuffer
= ByteBuffer.allocate(5);
// put byte value in byteBuffer
// using put() method
byteBuffer.put((byte)20);
byteBuffer.put((byte)30);
byteBuffer.put((byte)40);
// mark will be going to discard
// by rewind()
byteBuffer.mark();
// Typecast Bytebuffer to buffer
Buffer buffer = (Buffer)byteBuffer;
// print the buffer
System.out.println("Buffer before operation: "
+ Arrays.toString(
(byte[])buffer.array())
+ "\nPosition: "
+ buffer.position()
+ "\nLimit: "
+ buffer.limit());
// rewind the Buffer
// using rewind() method
buffer.rewind();
// print the bytebuffer
System.out.println("\nBuffer after operation: "
+ Arrays.toString(
(byte[])buffer.array())
+ "\nPosition: "
+ buffer.position()
+ "\nLimit: "
+ buffer.limit());
}
}
输出:
Buffer before operation: [20, 30, 40, 0, 0]
Position: 3
Limit: 5
Buffer after operation: [20, 30, 40, 0, 0]
Position: 0
Limit: 5
参考: https://docs.oracle.com/javase/9/docs/api/ Java/nio/Buffer.html#rewind–