Java中的 ByteBuffer flip() 方法及示例
Java.nio.ByteBuffer 类的flip()方法用于翻转这个缓冲区。限制设置为当前位置,然后位置设置为零。如果标记已定义,则将其丢弃。在一系列通道读取或放置操作之后,调用此方法以准备一系列通道写入或相关获取操作。
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
在将数据从一个地方传输到另一个地方时,此方法通常与紧凑方法结合使用。
句法:
public ByteBuffer flip()
返回值:此方法返回此缓冲区。
以下是说明翻转()方法的示例:
示例 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
示例 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–