Java FloatBuffer rewind()方法及示例

java.nio.FloatBuffer类的 rewind() 方法是用来倒退这个缓冲区的。该方法将位置设置为零，极限值不受影响，如果有任何先前标记的位置，将被丢弃。当有任何必要的通道写入或获取操作的序列时，应该调用这个方法。这意味着，如果缓冲区的数据已经被写入，那么它需要被复制到另一个数组中。比如说。

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

语法

public final FloatBuffer rewind()

参数： 该方法不接受任何参数。

返回值： 该方法返回这个缓冲区。

下面是说明rewind()方法的例子。

例子 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 FloatBuffer        // using allocate() method        FloatBuffer floatBuffer = FloatBuffer.allocate(4);          // put char value in FloatBuffer        // using put() method        floatBuffer.put(10.5f);        floatBuffer.put(20.5f);          // print the float buffer        System.out.println("Buffer before operation: "                           + Arrays.toString(                                 floatBuffer.array())                           + "\nPosition: "                           + floatBuffer.position()                           + "\nLimit: "                           + floatBuffer.limit());          // rewind the Buffer        // using rewind() method        floatBuffer.rewind();          // print the floatbuffer        System.out.println("\nBuffer after operation: "                           + Arrays.toString(                                 floatBuffer.array())                           + "\nPosition: "                           + floatBuffer.position()                           + "\nLimit: "                           + floatBuffer.limit());    }}

输出。

Buffer before operation: [10.5, 20.5, 0.0, 0.0]Position: 2Limit: 4Buffer after operation: [10.5, 20.5, 0.0, 0.0]Position: 0Limit: 4

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

输出。

Buffer before operation: [10.5, 20.5, 30.5, 0.0, 0.0]Position: 3Limit: 5Buffer after operation: [10.5, 20.5, 30.5, 0.0, 0.0]Position: 0Limit: 5

参考资料: https://docs.oracle.com/javase/9/docs/api/java/nio/FloatBuffer.html#rewind-