Java ByteBuffer asCharBuffer()方法及示例

java.nio.ByteBuffer 类的 asCharBuffer() 方法用于将此字节缓冲区创建为char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2，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 CharBuffer asCharBuffer()

返回值： 该方法返回一个新的char缓冲区。

以下是说明asCharBuffer()方法的例子：

例子1：

// Java program to demonstrate
// asCharBuffer() 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 view as char buffer
            // and putting a string value
            bb.asCharBuffer().put("TajMahal");
 
            // Declaring char variable c
            char c;
 
            // print the ByteBuffer
            System.out.print("Char buffer : ");
            while ((c = bb.getChar()) != 0)
                System.out.print(c + " ");
            System.out.println();
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception thrown : " + e);
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

Char buffer : T a j M a h a l

例2：

// Java program to demonstrate
// asCharBuffer() method
// for Read only 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
            // char buffer
            CharBuffer cb = bb.asCharBuffer();
 
            // putting the value in charbuffer
            cb.put("Tajmahal");
            cb.rewind();
 
            // Declaring variable c
            char c;
 
            // print the ByteBuffer
            System.out.print("Char buffer : ");
            while ((c = cb.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 char buffer
            CharBuffer cb1 = bb1.asCharBuffer();
 
            // putting the value in charbuffer
            System.out.println("\n\nTrying to put the string"
                               + " into read only charbuffer");
            cb1.put("Tajmahal");
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception thrown : " + e);
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

Char buffer : T a j m a h a l 

Trying to put the string into read only charbuffer
Exception thrown : java.nio.ReadOnlyBufferException