Java Buffer rewind()用法及代碼示例

java.nio.ByteBuffer類的rewind()方法用於倒帶此緩衝區。位置設置為零，標記被丟棄。假設已正確設置了限製，請在序列channel-write或get操作之前調用此方法。調用此方法既不會更改，也不會丟棄標記的值。

用法:

public ByteBuffer rewind()

返回值：此方法返回此緩衝區。

下麵是說明rewind()方法的示例：

範例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()); 
    } 
}

輸出：

Buffer before operation:[20, 97, 0, 0]
Position:2
Limit:4

Buffer after operation:[20, 97, 0, 0]
Position:0
Limit:4

範例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()); 
    } 
}

輸出：

Buffer before operation:[20, 30, 40, 0, 0]
Position:3
Limit:5

Buffer after operation:[20, 30, 40, 0, 0]
Position:0
Limit:5

參考： https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#rewind-

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注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 Buffer rewind() methods in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。