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