Java中的 LongBuffer arrayOffset() 方法

Java.nio.LongBuffer类的arrayOffset()方法用于返回缓冲区的第一个元素在缓冲区的后备数组中的偏移量。这意味着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()。

为了检查这个缓冲区是否有一个后备数组，可以使用hasArray()方法。它确保此缓冲区具有可访问的后备数组。

句法 ：

public final Long arrayOffset()

返回值：此方法返回缓冲区第一个元素在此缓冲区数组中的偏移量。

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

下面的程序说明了arrayOffset()方法。

方案一：

// 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 LongBuffer
        int capacity = 10;
  
        // Creating the LongBuffer
        try {
  
            // creating object of Longbuffer
            // and allocating size capacity
            LongBuffer ib = LongBuffer.allocate(capacity);
  
            // putting the value in Longbuffer
            ib.put(8);
            ib.put(2, 9);
  
            // prLong the LongBuffer
            System.out.println("LongBuffer: "
                               + Arrays.toString(ib.array()));
  
            // prLong the arrayOffset
            System.out.println("arrayOffset: "
                               + ib.arrayOffset());
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws" + e);
        }
    }
}

输出：

LongBuffer: [8, 0, 9, 0, 0, 0, 0, 0, 0, 0]
arrayOffset: 0

程序2：演示ReadOnlyBufferException。

// 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 LongBuffer
        int capacity = 10;
  
        // Creating the LongBuffer
        try {
  
            // creating object of Longbuffer
            // and allocating size capacity
            LongBuffer ib = LongBuffer.allocate(capacity);
  
            // putting the value in Longbuffer
            ib.put(8);
            ib.put(2, 9);
            ib.rewind();
  
            // Creating a read-only copy of LongBuffer
            // using asReadOnlyBuffer() method
            LongBuffer ib1 = ib.asReadOnlyBuffer();
  
            // prLong the LongBuffer
            System.out.print("Read only buffer : ");
            while (ib1.hasRemaining())
                System.out.print(ib1.get() + ", ");
  
            // next line
            System.out.println("");
  
            // prLong the arrayOffset
            System.out.println("\nTry to prLong the array offset"
                               + " of read only buffer");
            System.out.println("arrayOffset: " + ib1.arrayOffset());
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception throws: " + e);
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws: " + e);
        }
    }
}

输出：

Read only buffer : 8, 0, 9, 0, 0, 0, 0, 0, 0, 0, 

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