Java中的CharBuffer hasArray()方法

Java.nio.CharBuffer类的hasArray()方法用于确保给定缓冲区是否由可访问的 char 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()

返回值：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 CharBuffer
        int capacity = 10;
  
        // Creating the CharBuffer
        try {
  
            // creating object of Intbuffer
            // and allocating size capacity
            CharBuffer cb = CharBuffer.allocate(capacity);
  
            // putting the value in Intbuffer
            cb.put('a');
            cb.put(2, 'b');
            cb.rewind();
  
            // checking CharBuffer cb is backed by array or not
            boolean isArray = cb.hasArray();
  
            // checking if else condition
            if (isArray)
                System.out.println("CharBuffer cb is"
                                   + " backed by array");
            else
                System.out.println("CharBuffer cb is"
                                   + " not backed by any array");
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出：

CharBuffer cb is backed by array

示例 2：当缓冲区没有数组支持时

// 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 CharBuffer
        int capacity = 10;
  
        // Creating the CharBuffer
        try {
  
            // creating object of CharBuffer
            // and allocating size capacity
            CharBuffer cb = CharBuffer.allocate(capacity);
  
            // putting the value in CharBuffer
            cb.put('a');
            cb.put(2, 'b');
            cb.rewind();
  
            // Creating a read-only copy of CharBuffer
            // using asReadOnlyBuffer() method
            CharBuffer cb1 = cb.asReadOnlyBuffer();
  
            // checking CharBuffer cb is backed by array or not
            boolean isArray = cb1.hasArray();
  
            // checking if else condition
            if (isArray)
                System.out.println("CharBuffer cb is"
                                   + " backed by array");
            else
                System.out.println("CharBuffer cb is"
                                   + " not backed by any array");
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出：

CharBuffer cb is not backed by any array