Java中的DoubleBuffer hasArray（）方法及其示例-yiteyi-C++库

这个 hasArray（） 方法 JAVA尼奥。双缓冲区 类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备份数组，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，因为它们在支持数组上工作。

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语法：

public final boolean hasArray()

返回： 此方法将返回 符合事实的 当且仅当此缓冲区由数组支持且不是只读的。否则它就会回来 错误的

下面是hasArray（）方法的示例：

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

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

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