Java DoubleBuffer hasArray()方法及示例

java.nio.DoubleBuffer 类的 hasArray() 方法用于确保给定的缓冲区是否有一个可访问的浮动数组作为支撑。如果这个缓冲区有一个可访问的支持数组，它就返回true，否则就返回false。如果该方法返回true，那么可以安全地调用array()和arrayOffset()方法，因为它们对支持数组起作用。

语法

public final boolean hasArray()

返回： 当且仅当该缓冲区由一个数组支持并且不是只读时，该方法将返回 true 。否则，它将返回 false 。

下面是说明hasArray()方法的例子。

例子1： 当缓冲区由一个数组支持时

// Java program to demonstrate
// hasArray() 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();
  
            // checking DoubleBuffer fb is backed by array or not
            boolean isArray = fb.hasArray();
  
            // checking if else condition
            if (isArray)
                System.out.println("DoubleBuffer fb is"
                                   + " backed by array");
            else
                System.out.println("DoubleBuffer fb is"
                                   + " not backed by any array");
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出:

DoubleBuffer fb is backed by array

例子2： 当缓冲区由一个数组支持时

// Java program to demonstrate
// hasArray() 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();
  
            // checking DoubleBuffer fb is backed by array or not
            boolean isArray = fb1.hasArray();
  
            // checking if else condition
            if (isArray)
                System.out.println("DoubleBuffer fb is"
                                   + " backed by array");
            else
                System.out.println("DoubleBuffer fb is"
                                   + " not backed by any array");
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出:

DoubleBuffer fb is not backed by any array