Java ByteBuffer hasArray()用法及代碼示例

java.nio.ByteBuffer類的hasArray()方法用於確保給定緩衝區是否由可訪問的字節數組支持。如果此緩衝區有可訪問的後備數組，則返回true，否則返回false。如果此方法返回true，則可以安全地調用array()和arrayOffset()方法，因為它們在支持數組上起作用。

用法:

public final boolean hasArray()

返回值：當且僅當此緩衝區由數組支持並且不是隻讀時，此方法才會返回true。否則返回false。

下麵是說明hasArray()方法的示例：

範例1：當緩衝區由數組支持時

// 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 ByteBuffer 
        int capacity = 10; 
  
        // Creating the ByteBuffer 
        try { 
  
            // creating object of bytebuffer 
            // and allocating size capacity 
            ByteBuffer bb = ByteBuffer.allocate(capacity); 
  
            // putting the value in bytebuffer 
            bb.put((byte)10); 
            bb.put((byte)20); 
            bb.rewind(); 
  
            // checking FloatBuffer fb is backed by array or not 
            boolean isArray = bb.hasArray(); 
  
            // checking if else condition 
            if (isArray) 
                System.out.println("ByteBuffer bb is"
                                   + " backed by array"); 
            else
                System.out.println("ByteBuffer bb is"
                                   + " not backed by any array"); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("IllegalArgumentException catched"); 
        } 
  
        catch (ReadOnlyBufferException e) { 
            System.out.println("ReadOnlyBufferException catched"); 
        } 
    } 
}

輸出：

ByteBuffer bb is backed by array

範例2：當緩衝區由數組支持時

// 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 ByteBuffer 
        int capacity = 10; 
  
        // Creating the ByteBuffer 
        try { 
  
            // creating object of ByteBuffer 
            // and allocating size capacity 
            ByteBuffer bb = ByteBuffer.allocate(capacity); 
  
            // putting the value in ByteBuffer 
            bb.put((byte)8.56F); 
            bb.put((byte)10); 
            bb.rewind(); 
  
            // Creating a read-only copy of ByteBuffer 
            // using asReadOnlyBuffer() method 
            ByteBuffer bb1 = bb.asReadOnlyBuffer(); 
  
            // checking ByteBuffer bb is backed by array or not 
            boolean isArray = bb1.hasArray(); 
  
            // checking if else condition 
            if (isArray) 
                System.out.println("ByteBuffer bb is"
                                   + " backed by array"); 
            else
                System.out.println("ByteBuffer bb is"
                                   + " not backed by any array"); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("IllegalArgumentException catched"); 
        } 
  
        catch (ReadOnlyBufferException e) { 
            System.out.println("ReadOnlyBufferException catched"); 
        } 
    } 
}

輸出：

ByteBuffer bb is not backed by any array

參考： https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#hasArray–

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注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 ByteBuffer hasArray() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。