Java DoubleBuffer rewind()方法及示例
java.nio.DoubleBuffer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,应调用该方法。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 remaining data
buf.rewind(); // Rewind the buffer
buf.get(array); // Copy the data into array
语法
public final DoubleBuffer 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 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
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 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
参考资料: https://docs.oracle.com/javase/9/docs/api/java/nio/DoubleBuffer.html#rewind-