Java 中的 DoubleBuffer 倒带()方法，示例
原文:https://www . geesforgeks . org/double buffer-rewind-in-Java-method-with-examples/
java.nio.DoubleBuffer 类的倒带()方法用来倒带这个缓冲区。此方法将位置设置为零，限制不受影响，如果有任何先前标记的位置，将被丢弃。 当需要进行通道写或获取操作时，应调用该方法。这意味着，如果缓冲区数据已经写入，则需要将其复制到另一个数组中。例如:
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:该方法不取任何参数。
返回值:这个方法返回这个缓冲区。
以下是说明 rewind()方法的示例:
实施例 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());
}
}
Output:
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
实施例 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());
}
}
Output:
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:https://docs . Oracle . com/javase/9/docs/API/Java/nio/double buffer . html # rewind–
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