Java IntBuffer arrayOffset()方法

java.nio.IntBuffer 类的 arrayOffset() 方法是用来返回缓冲区的第一个元素在缓冲区的支持数组中的偏移。这意味着如果这个缓冲区是由一个数组支持的，那么缓冲区的位置p对应于数组索引p + arrayOffset()。

为了检查这个缓冲区是否有一个支持的数组，可以使用 hasArray() 方法。它可以确保这个缓冲区有一个可访问的支持数组。

语法:

public final int arrayOffset()

返回值： 该方法返回该缓冲区的第一个元素在该缓冲区的数组中的偏移。

异常： 如果这个缓冲区是由一个数组支持的，但是是只读的，这个方法会抛出 ReadOnlyBufferException 。

下面的程序说明了 arrayOffset() 方法。

例子 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 IntBuffer
        int capacity = 10;
  
        // Creating the IntBuffer
        try {
  
            // creating object of Intbuffer
            // and allocating size capacity
            IntBuffer ib = IntBuffer.allocate(capacity);
  
            // putting the value in Intbuffer
            ib.put(8);
            ib.put(2, 9);
  
            // print the IntBuffer
            System.out.println("IntBuffer: "
                               + Arrays.toString(ib.array()));
  
            // print 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:

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

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