Java DoubleBuffer rewind()用法及代码示例

java.nio.DoubleBuffer类的rewind()方法用于倒带此缓冲区。此方法将位置设置为零，并且限制不受影响，并且如果有任何先前标记的位置将被丢弃。
当需要对channel-write进行序列化或进行get操作时，应调用此方法。这意味着，如果已经写入了缓冲区数据，则需要将其复制到另一个数组中。例如：

 
out.write(buf);    // Writes remaining data
buf.rewind();      // Rewind the buffer
buf.get(array);    // Copy the data into array

用法:

public final DoubleBuffer rewind()

参数：该方法不带任何参数。

返回值：此方法返回此缓冲区。

下面是说明rewind()方法的示例：

范例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 DoubleBuffer 
        // using allocate() method 
        DoubleBuffer doubleBuffer = DoubleBuffer.allocate(4); 
  
        // put char value in doubleBuffer 
        // using put() method 
        doubleBuffer.put(10.5); 
        doubleBuffer.put(20.5); 
  
        // print the double buffer 
        System.out.println("Buffer before operation: "
                           + Arrays.toString( 
                                 doubleBuffer.array()) 
                           + "\nPosition: "
                           + doubleBuffer.position() 
                           + "\nLimit: "
                           + doubleBuffer.limit()); 
  
        // rewind the Buffer 
        // using rewind() method 
        doubleBuffer.rewind(); 
  
        // print the doublebuffer 
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString( 
                                 doubleBuffer.array()) 
                           + "\nPosition: "
                           + doubleBuffer.position() 
                           + "\nLimit: "
                           + doubleBuffer.limit()); 
    } 
}

输出：

Buffer before operation: [10.5, 20.5, 0.0, 0.0]
Position: 2
Limit: 4

Buffer after operation: [10.5, 20.5, 0.0, 0.0]
Position: 0
Limit: 4

范例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 DoubleBuffer 
        // using allocate() method 
        DoubleBuffer doubleBuffer 
            = DoubleBuffer.allocate(5); 
  
        // put double value in doubleBuffer 
        // using put() method 
        doubleBuffer.put(10.5); 
        doubleBuffer.put(20.5); 
        doubleBuffer.put(30.5); 
  
        // mark will be going to discarded by rewind() 
        doubleBuffer.mark(); 
  
        // print the buffer 
        System.out.println("Buffer before operation: "
                           + Arrays.toString( 
                                 doubleBuffer.array()) 
                           + "\nPosition: "
                           + doubleBuffer.position() 
                           + "\nLimit: "
                           + doubleBuffer.limit()); 
  
        // Rewind the Buffer 
        // using rewind() method 
        doubleBuffer.rewind(); 
  
        // print the buffer 
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString( 
                                 doubleBuffer.array()) 
                           + "\nPosition: "
                           + doubleBuffer.position() 
                           + "\nLimit: "
                           + doubleBuffer.limit()); 
    } 
}

输出：

Buffer before operation: [10.5, 20.5, 30.5, 0.0, 0.0]
Position: 3
Limit: 5

Buffer after operation: [10.5, 20.5, 30.5, 0.0, 0.0]
Position: 0
Limit: 5

参考： https://docs.oracle.com/javase/9/docs/api/java/nio/DoubleBuffer.html#rewind–

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注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 DoubleBuffer rewind() Method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。