Java ByteBuffer allocate()用法及代码示例

java.nio.ByteBuffer类的allocate()方法用于分配新的字节缓冲区。

新缓冲区的位置将为零，其极限将是其容量，其标记将是未定义的，并且其每个元素都将初始化为零。它将有一个支持数组，其数组偏移量将为零。

用法:

public static ByteBuffer allocate(int capacity)

参数：此方法将容量(以字节为单位)作为参数。

返回值：此方法返回新的字节缓冲区。

抛出：如果容量为负整数，则此方法抛出IllegalArgumentException

下面是说明allocate()方法的示例：

范例1：

// Java program to demonstrate 
// allocate() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // Declaring the capacity of the ByteBuffer 
        int capacity = 4; 
  
        // Creating the ByteBuffer 
        try { 
  
            // creating object of ByteBuffer 
            // and allocating size capacity 
            ByteBuffer bb = ByteBuffer.allocate(capacity); 
  
            // putting the int to byte typecast value 
            // in ByteBuffer using putInt() method 
            bb.put((byte)20); 
            bb.put((byte)30); 
            bb.put((byte)40); 
            bb.put((byte)50); 
            bb.rewind(); 
  
            // print the ByteBuffer 
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb.array())); 
        } 
  
        catch (IllegalArgumentException e) { 
  
            System.out.println("IllegalArgumentException catched"); 
        } 
  
        catch (ReadOnlyBufferException e) { 
  
            System.out.println("ReadOnlyBufferException catched"); 
        } 
    } 
}

输出：

Original ByteBuffer:  [20, 30, 40, 50]

范例2：

// Java program to demonstrate 
// allocate() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // Declaring the capacity with negative 
        // value of the ByteBuffer 
        int capacity = -4; 
  
        // Creating the ByteBuffer 
        try { 
  
            // creating object of ByteBuffer 
            // and allocating size capacity 
            System.out.println("Trying to allocate negative"+ 
                                         " value in ByteBuffer"); 
            ByteBuffer bb = ByteBuffer.allocate(capacity); 
  
            // putting int to byte typecast value 
            // in ByteBuffer using putInt() method 
            bb.put((byte)20); 
            bb.put((byte)30); 
            bb.put((byte)40); 
            bb.put((byte)50); 
            bb.rewind(); 
  
            // print the ByteBuffer 
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb.array())); 
        } 
  
        catch (IllegalArgumentException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
  
        catch (ReadOnlyBufferException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

输出：

Trying to allocate negative value in ByteBuffer
Exception thrown : java.lang.IllegalArgumentException

相关用法

注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 ByteBuffer allocate() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。