Java 中的缓冲倒带()方法，示例
原文:https://www . geesforgeks . org/buffer-rewind-methods-in-Java-with-examples/
java.nio.ByteBuffer 类的倒带()方法用来倒带这个缓冲区。位置设置为零，标记被丢弃。假设已经适当地设置了限制，则在一系列通道写入或获取操作之前调用此方法。调用此方法既不会改变也不会丢弃标记的值。
语法:
public ByteBuffer rewind()
返回值:这个方法返回这个缓冲区。
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–
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