Java ByteBuffer asLongBuffer()方法及示例

java.nio.ByteBuffer 类的 asLongBuffer() 方法用于将此字节缓冲区创建为一个长缓冲区的视图。

新缓冲区的内容将从此缓冲区的当前位置开始。这个缓冲区内容的变化将在新的缓冲区中可见，反之亦然；两个缓冲区的位置、极限和标记值将是独立的。

新缓冲区的位置将是0，其容量和极限将是这个缓冲区中剩余的字节数除以8，其标记将是未定义的。当且仅当这个缓冲区是直接的，新的缓冲区将是直接的，当且仅当这个缓冲区是只读的，它将是只读的。

语法：

public abstract LongBuffer asLongBuffer()

返回值： 该方法返回一个新的长缓冲区。

以下是说明asLongBuffer()方法的例子：

例子1：

// Java program to demonstrate
// asLongBuffer() method
// for ByteBuffer
 
import java.nio.*;
import java.util.*;
 
public class GFG {
 
    public static void main(String[] args)
    {
 
        // Declaring the capacity  of the ByteBuffer
        int capacity = 50;
 
        // Creating the ByteBuffer
        try {
 
            // creating object of  ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.allocate(capacity);
 
            // changing  bytebuffer into
            // LongBuffer
            LongBuffer lb = bb.asLongBuffer();
 
            // putting the value in LongBuffer
            lb.put(1000000);
            lb.put(2000000);
            lb.put(3000000);
            lb.put(3000000);
            lb.rewind();
 
            // Declaring variable c
            long c;
 
            // print the ByteBuffer
            System.out.print("LongBuffer : ");
            while ((c = lb.get()) != 0)
                System.out.print(c + "  ");
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception thrown : " + e);
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

LongBuffer : 1000000  2000000  3000000  3000000

实例2：

// Java program to demonstrate
// asLongBuffer() method
// for ByteBuffer
 
import java.nio.*;
import java.util.*;
 
public class GFG {
 
    public static void main(String[] args)
    {
 
        // Declaring the capacity  of the ByteBuffer
        int capacity = 50;
 
        // Creating the ByteBuffer
        try {
 
            // creating object of  ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.allocate(capacity);
 
            // changing  bytebuffer into
            // LongBuffer
            LongBuffer lb = bb.asLongBuffer();
 
            // putting the value in LongBuffer
            lb.put(1000000);
            lb.put(2000000);
            lb.put(3000000);
            lb.rewind();
 
            // Declaring variable c
            long c;
 
            // print the ByteBuffer
            System.out.print("LongBuffer : ");
            while ((c = lb.get()) != 0)
                System.out.print(c + "  ");
 
            // Creating a read-only copy of ByteBuffer
            // using asReadOnlyBuffer() method
            ByteBuffer bb1 = bb.asReadOnlyBuffer();
 
            // changing read-only bytebuffer into
            // read-only LongBuffer
            LongBuffer lb1 = bb1.asLongBuffer();
 
            // putting the value in read-only LongBuffer
            System.out.println("\n\nTrying to put the value "
                               + "in read only LongBuffer");
            lb1.put(10);
            lb1.put(20);
            lb1.put(30);
            lb1.rewind();
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception thrown : " + e);
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

LongBuffer : 1000000  2000000  3000000  

Trying to put the value in read only LongBuffer
Exception thrown : java.nio.ReadOnlyBufferException