Java Buffer mark()方法及示例

java.nio.Buffer类的 mark() 方法用于在其位置上设置这个缓冲区的标记。

语法：

public Buffer mark()

返回值： 该方法返回这个缓冲区。
以下是说明mark()方法的例子：

例子1：

// Java program to demonstrate// mark() method import java.nio.*;import java.util.*; public class GFG {     public static void main(String[] args)    {         try {             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            bb1.position(2);             // Set this buffer mark position            // using mark() method            bb1.mark();             // try to set the position at index 4            bb1.position(4);             // display position            System.out.println("position before reset: "                               + bb1.position());             // try to call reset() to restore            // to the position we marked            bb1.reset();             // display position            System.out.println("position after reset: "                               + bb1.position());        }         catch (InvalidMarkException e) {            System.out.println("new position is less than "                               + "the position we marked before ");            System.out.println("Exception throws: " + e);        }    }}

输出

position before reset: 4position after reset: 2

实例2： 为了证明InvalidMarkException

// Java program to demonstrate// mark() method import java.nio.*;import java.util.*; public class GFG {     public static void main(String[] args)    {         try {             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            bb1.position(2);             // Set this buffer mark position            // using mark() method            bb1.mark();             // try to set the position at index 4            bb1.position(1);             // display position            System.out.println("position before reset: "                               + bb1.position());             // try to call reset() to restore            // to the position we marked            bb1.reset();             // display position            System.out.println("position after reset: "                               + bb1.position());        }         catch (InvalidMarkException e) {            System.out.println("\new position is less than "                               + "the position we marked before ");            System.out.println("Exception throws: " + e);        }    }}

输出

position before reset: 1new position is less than the position we marked before Exception throws: java.nio.InvalidMarkException

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