Java ByteBuffer mark()用法及代碼示例

java.nio.ByteBuffer類的mark()方法用於將該緩衝區的標記設置在其位置。

用法:

public ByteBuffer mark()

返回值：此方法返回此緩衝區。

下麵是說明mark()方法的示例：

範例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); 
  
            // try to set the position at index 2 
            bb.position(2); 
  
            // Set this buffer mark position 
            // using mark() method 
            bb.mark(); 
  
            // try to set the position at index 4 
            bb.position(4); 
  
            // display position 
            System.out.println("position before reset:"
                               + bb.position()); 
  
            // try to call reset() to restore 
            // to the position we marked 
            bb.reset(); 
  
            // display position 
            System.out.println("position after reset:"
                               + bb.position()); 
        } 
  
        catch (InvalidMarkException e) { 
            System.out.println("new position is less than "
                               + "the position we marked before "); 
            System.out.println("Exception throws:" + e); 
        } 
    } 
}

輸出：

position before reset:4
position after reset:2

範例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 { 
  
            byte[] barr = { 10, 20, 30, 40 }; 
  
            // creating object of ByteBuffer 
            // and allocating size capacity 
            ByteBuffer bb = ByteBuffer.wrap(barr); 
  
            // try to set the position at index 2 
            bb.position(2); 
  
            // Set this buffer mark position 
            // using mark() method 
            bb.mark(); 
  
            // try to set the position at index 4 
            bb.position(1); 
  
            // display position 
            System.out.println("position before reset:"
                               + bb.position()); 
  
            // try to call reset() to restore 
            // to the position we marked 
            bb.reset(); 
  
            // display position 
            System.out.println("position after reset:"
                               + bb.position()); 
        } 
  
        catch (InvalidMarkException e) { 
            System.out.println("\nnew position is less than "
                               + "the position we marked before "); 
            System.out.println("Exception throws:" + e); 
        } 
    } 
}

輸出：

position before reset:1

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

參考： https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#mark-

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注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 ByteBuffer mark() methods in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。