Java中的DoubleBuffer arrayOffset()方法示例

Java.nio.DoubleBuffer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 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。

示例 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 DoubleBuffer
        int capacity = 10;
  
        // Creating the DoubleBuffer
        try {
  
            // creating object of Doublebuffer
            // and allocating size capacity
            DoubleBuffer fb = DoubleBuffer.allocate(capacity);
  
            // putting the value in Doublebuffer
            fb.put(8.56F);
            fb.put(2, 9.61F);
  
            // print the DoubleBuffer
            System.out.println("DoubleBuffer: "
                               + Arrays.toString(fb.array()));
  
            // print the arrayOffset
            System.out.println("arrayOffset: "
                               + fb.arrayOffset());
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws" + e);
        }
    }
}

输出：

DoubleBuffer: [8.5600004196167, 0.0, 9.609999656677246, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
arrayOffset: 0

示例 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 DoubleBuffer
        int capacity = 10;
  
        // Creating the DoubleBuffer
        try {
  
            // creating object of Doublebuffer
            // and allocating size capacity
            DoubleBuffer fb = DoubleBuffer.allocate(capacity);
  
            // putting the value in Doublebuffer
            fb.put(8.56F);
            fb.put(2, 9.61F);
            fb.rewind();
  
            // Creating a read-only copy of DoubleBuffer
            // using asReadOnlyBuffer() method
            DoubleBuffer fb1 = fb.asReadOnlyBuffer();
  
            // print the DoubleBuffer
            System.out.print("Read only buffer : ");
            while (fb1.hasRemaining())
                System.out.print(fb1.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: " + fb1.arrayOffset());
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception throws: " + e);
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws: " + e);
        }
    }
}

输出：

Read only buffer : 8.5600004196167, 0.0, 9.609999656677246, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 

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