Java ByteBuffer flip()用法及代码示例

java.nio.ByteBuffer类的flip()方法用于翻转此缓冲区。将限制设置为当前位置，然后将该位置设置为零。如果定义了标记，则将其丢弃。在序列完成channel-read或放置操作之后，调用此方法为序列进行准备的channel-write或相对get操作。

例如：

buf.put(magic);    // Prepend header
in.read(buf);      // Read data into rest of buffer
buf.flip();        // Flip buffer
out.write(buf);    // Write header + data to channel

当将数据从一个地方传输到另一个地方时，通常将此方法与紧凑方法结合使用。

用法:

public ByteBuffer flip()

返回值：此方法返回此缓冲区。

下面是说明flip()方法的示例：

范例1：

// Java program to demonstrate 
// flip() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Declare and initialize the byte array 
        byte[] bb = { 10, 20, 30 }; 
  
        // wrap the byte array into floatBuffer 
        // using wrap() method 
        ByteBuffer byteBuffer = ByteBuffer.wrap(bb); 
  
        // set position at index 1 
        byteBuffer.position(1); 
  
        // print the byte buffer 
        System.out.println("ByteBuffer before flip:"
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition:" + byteBuffer.position() 
                           + "\nLimit:" + byteBuffer.limit()); 
  
        // Flip the byteBuffer 
        // using flip() method 
        byteBuffer.flip(); 
  
        // print the byte buffer 
        System.out.println("\nByteBuffer after flip:"
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition:" + byteBuffer.position() 
                           + "\nLimit:" + byteBuffer.limit()); 
    } 
}

输出：

ByteBuffer before flip:[10, 20, 30]
Position:1
Limit:3

ByteBuffer after flip:[10, 20, 30]
Position:0
Limit:1

输出：

ByteBuffer before flip:[10, 20, 30]
Position:1
Limit:3

ByteBuffer after flip:[10, 20, 30]
Position:0
Limit:1

范例2：

// Java program to demonstrate 
// flip() 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)30); 
  
        // print the byte buffer 
        System.out.println("ByteBuffer before flip:"
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition:" + byteBuffer.position() 
                           + "\nLimit:" + byteBuffer.limit()); 
  
        // Flip the byteBuffer 
        // using flip() method 
        byteBuffer.flip(); 
  
        // print the byte buffer 
        System.out.println("\nByteBuffer after flip:"
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition:" + byteBuffer.position() 
                           + "\nLimit:" + byteBuffer.limit()); 
    } 
}

输出：

ByteBuffer before flip:[20, 30, 0, 0]
Position:2
Limit:4

ByteBuffer after flip:[20, 30, 0, 0]
Position:0
Limit:2

参考： https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#flip-

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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 ByteBuffer flip() methods 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。