Java FloatBuffer mark()方法及示例

java.nio.FloatBuffer类的 mark() 方法是用来标记这个FloatBuffer的当前位置，作为这个缓冲区的标记。

语法

public final FloatBuffer mark()

参数： 该方法不接受任何参数。

返回值： 该方法在将缓冲区的标记设置在当前位置后返回该FloatBuffer。

下面的例子说明了mark()方法。

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 {              float[] farr = { 10.5f, 20.5f, 30.5f, 40.5f };              // creating object of FloatBuffer            // and allocating size capacity            FloatBuffer fb = FloatBuffer.wrap(farr);              // try to set the position at index 2            fb.position(2);              // Set this buffer mark position            // using mark() method            fb.mark();              // try to set the position at index 4            fb.position(4);              // display position            System.out.println("position before reset: "                               + fb.position());              // try to call reset() to restore            // to the position we marked            fb.reset();              // display position            System.out.println("position after reset: "                               + fb.position());        }          catch (InvalidMarkException e) {            System.out.println("New position "                               + "is less than "                               + "the position "                               + "marked before ");            System.out.println("Exception throws: "                               + e);        }    }}

输出。

position before reset: 4position after reset: 2

实例2： 演示InvalidMarkException

// Java program to demonstrate// mark() method  import java.nio.*;import java.util.*;  public class GFG {      public static void main(String[] args)    {          try {              float[] farr = { 10.5f, 20.5f, 30.5f, 40.5f };              // creating object of FloatBuffer            // and allocating size capacity            FloatBuffer fb = FloatBuffer.wrap(farr);              // try to set the position at index 2            fb.position(2);              // Set this buffer mark position            // using mark() method            fb.mark();              // try to set the position at index 1            fb.position(1);              // display position            System.out.println("position before reset: "                               + fb.position());              // try to call reset() to restore            // to the position we marked            fb.reset();              // display position            System.out.println("position after reset: "                               + fb.position());        }          catch (InvalidMarkException e) {            System.out.println("\nNew position "                               + "is less than "                               + "the position "                               + "marked before ");            System.out.println("Exception throws: "                               + e);        }    }}

输出。

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

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