Java中的 DoubleBuffer hasArray() 方法及示例

Java.nio.DoubleBuffer类的hasArray()方法用于确保给定缓冲区是否由可访问的浮点数组支持。如果此缓冲区有可访问的支持数组，则返回 true，否则返回 false。如果此方法返回 true，则可以安全地调用 array() 和 arrayOffset() 方法，因为它们在后备数组上工作。

句法：

public final boolean hasArray()

返回：当且仅当此缓冲区由数组支持并且不是只读的时，此方法才会返回true 。否则返回false。

下面是说明 hasArray() 方法的示例：

示例 1：当缓冲区由数组支持时

// 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

示例 2：当缓冲区由数组支持时

// 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