极客教程Java Buffer position()方法及示例
java.nio.Buffer类 的 position(int newPosition) 方法是用来设置这个缓冲区的位置。如果标记被定义并且大于新的位置，那么它将被丢弃。
语法
public Buffer position(int newPosition)Java
参数。该方法以newPosition为参数，是新的位置值。它必须是非负值，并且不大于当前的限制。
返回值： 该方法返回这个缓冲区。
下面是说明 position() 方法的例子。
例子 1 :
// Java program to demonstrate
// position() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
byte[] barr = { 10, 20, 30, 40 };
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.wrap(barr);
// Typecasting ByteBuffer into Buffer
Buffer bb1 = (Buffer)bb;
// try to set the position at index 2
// using position() method
bb1.position(2);
// Set this buffer mark position
bb1.mark();
// try to set the position at index 4
// using position() method
bb1.position(4);
// display position
System.out.println("position before reset: "
+ bb.position());
// try to call reset() to restore
// to the position we marked
bb1.reset();
// display position
System.out.println("position after reset: "
+ bb1.position());
}
}Java
输出:
position before reset: 4
position after reset: 2Java
例子 2 :
// Java program to demonstrate
// position() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(4);
// Typecasting ByteBuffer into Buffer
Buffer bb1 = (Buffer)bb;
// try to set the position at index 1
// using position() method
bb1.position(3);
// display position
System.out.println("position before clear: "
+ bb1.position());
// try to clear the Buffer
// using clear() method
bb1.clear();
// display position
System.out.println("position after clear: "
+ bb1.position());
}
}Java
输出:
position before clear: 3
position after clear: 0Java
参考资料: https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#position-int-