Java ByteBuffer arrayOffset()用法及代码示例

java.nio.ByteBuffer类的arrayOffset()方法用于返回给定缓冲区的第一个元素的后备数组内的偏移量。

如果此缓冲区由数组支持，则缓冲区位置p对应于数组索引p + arrayOffset()。

在调用此方法之前，请先调用hasArray方法，以确保此缓冲区具有可访问的后备数组。

用法:

public final int arrayOffset()

返回值：此方法返回缓冲区第一个元素在此缓冲区数组内的偏移量

异常：：如果此缓冲区由数组支持但为只读，则此方法引发ReadOnlyBufferException。

下面是说明arrayOffset()方法的示例：

范例1：

// Java program to demonstrate 
// arrayOffset() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Declaring the capacity of the ByteBuffer 
        int capacity = 4; 
  
        // Creating the ByteBuffer 
        try { 
  
            // creating object of ByteBuffer 
            // and allocating size capacity 
            ByteBuffer bb = ByteBuffer.allocate(capacity); 
  
            // putting the int to byte typecast value in ByteBuffer 
            bb.put((byte)20); 
            bb.put((byte)30); 
            bb.put((byte)40); 
            bb.put((byte)50); 
            bb.rewind(); 
  
            // print the ByteBuffer 
            System.out.println("ByteBuffer: "
                               + Arrays.toString(bb.array())); 
  
            // print the arrayOffset 
            System.out.println("arrayOffset: "
                               + bb.arrayOffset()); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("IllegalArgumentException catched"); 
        } 
  
        catch (ReadOnlyBufferException e) { 
            System.out.println("Exception throws" + e); 
        } 
    } 
}

输出：

ByteBuffer: [20, 30, 40, 50]
arrayOffset: 0

范例2：

// Java program to demonstrate 
// arrayOffset() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Declaring the capacity of the  ByteBuffer 
        int capacity = 3; 
  
        // Creating the  ByteBuffer 
        try { 
  
            // creating object of  ByteBuffer 
            // and allocating size capacity 
            ByteBuffer bb = ByteBuffer.allocate(capacity); 
  
            // putting the value in  ByteBuffer 
            bb.put((byte)20); 
            bb.put((byte)30); 
            bb.put((byte)40); 
            bb.rewind(); 
  
            // Creating a read-only copy of  ByteBuffer 
            // using asReadOnlyBuffer() method 
            ByteBuffer bb1 = bb.asReadOnlyBuffer(); 
  
            // print the  ByteBuffer 
            System.out.print("Read only buffer : "); 
            while (bb1.hasRemaining()) 
                System.out.print(bb1.get() + ", "); 
  
            // next line 
            System.out.println(""); 
  
            // print the arrayOffset 
            System.out.println("\nTry to print the array offset"
                               + " of read only buffer"); 
            System.out.println("arrayOffset: " + bb1.arrayOffset()); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("Exception throws: " + e); 
        } 
  
        catch (ReadOnlyBufferException e) { 
            System.out.println("Exception throws: " + e); 
        } 
    } 
}

输出：

Read only buffer : 20, 30, 40, 

Try to print the array offset of read only buffer
Exception throws: java.nio.ReadOnlyBufferException

相关用法

注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 ByteBuffer arrayOffset() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。