Java 中的缓冲区翻转()方法，示例
原文:https://www . geesforgeks . org/buffer-flip-methods-in-Java-with-examples/
java.nio.ByteBuffer 类 的 flip() 方法用来翻转这个缓冲区。极限被设置为当前位置，然后位置被设置为零。如果标记被定义，那么它被丢弃。在一系列通道读取或放置操作之后，调用此方法为一系列通道写入或相关的获取操作做准备。
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
当从一个地方向另一个地方传输数据时，此方法通常与 compact()方法结合使用。
语法:
public Buffer flip()
返回值:这个方法返回这个缓冲区。
下面是一些示例来说明 flip()方法:
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 ByteBuffer
// using wrap() method
ByteBuffer byteBuffer = ByteBuffer.wrap(bb);
// Typecast ByteBuffer to Buffer
Buffer buffer = (Buffer)byteBuffer;
// set position at index 1
buffer.position(1);
// print the buffer
System.out.println("Buffer before flip: "
+ Arrays.toString((byte[])buffer.array())
+ "\nPosition: " + buffer.position()
+ "\nLimit: " + buffer.limit());
// Flip the Buffer
// using flip() method
buffer.flip();
// print the buffer
System.out.println("\nBuffer after flip: "
+ Arrays.toString((byte[])buffer.array())
+ "\nPosition: " + buffer.position()
+ "\nLimit: " + buffer.limit());
}
}
输出:
Buffer before flip: [10, 20, 30]
Position: 1
Limit: 3
Buffer 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);
// Typecast ByteBuffer to Buffer
Buffer buffer = (Buffer)byteBuffer;
// set position at index 1
buffer.position(1);
// print the buffer
System.out.println("Buffer before flip: "
+ Arrays.toString((byte[])buffer.array())
+ "\nPosition: " + buffer.position()
+ "\nLimit: " + buffer.limit());
// Flip the Buffer
// using flip() method
buffer.flip();
// print the buffer
System.out.println("\nBuffer after flip: "
+ Arrays.toString((byte[])buffer.array())
+ "\nPosition: " + buffer.position()
+ "\nLimit: " + buffer.limit());
}
}
输出:
Buffer before flip: [20, 30, 0, 0]
Position: 1
Limit: 4
Buffer after flip: [20, 30, 0, 0]
Position: 0
Limit: 1
参考:https://docs . Oracle . com/javase/9/docs/API/Java/nio/buffer . html # flip–
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