What is the ByteBuffer.asCharBuffer() method in Java?
The java.nio.ByteBuffer class provides the asCharBuffer() method to create a char view-buffer of the underlying byte array of the original buffer.
A view-buffer is another buffer that is backed by the same array as the corresponding ByteBuffer object. Any changes made to the original ByteBuffer or the corresponding view-buffer are visible in both places. However, the position, limit, and mark of the two buffers are independent of each other.
Properties
-
The
positionof the new buffer is zero. It defines the byte index from which the next value will be read from the buffer. -
The
capacityandlimitof the new buffer are given by the number of remaining bytes divided by two. Thecapacityis the index of the last byte in the buffer. Thelimitis the index of the first index that should not be read from the buffer. -
The
markwill be undefined. This marks the current index of the buffer so that we can return to it when thereset()method is called. -
The new buffer will only be direct if this buffer is also direct.
-
The new buffer is only read-only if this buffer is also read-only.
Syntax
public abstract CharBuffer asCharBuffer()
Parameters
asCharBuffer() does not take any arguments.
Return value
asCharBuffer() returns a new CharBuffer view.
Code
import java.nio.*;import java.util.*;class main {public static void main( String args[] ) {ByteBuffer buffer = ByteBuffer.allocate(8);CharBuffer charBuff = buffer.asCharBuffer();charBuff.put('a');charBuff.put('b');charBuff.put('c');charBuff.put('d');charBuff.rewind();System.out.print("using CharBuffer: ");for(int i = buffer.position(); i < buffer.limit()/2; i++){System.out.print(buffer.getChar() + " ");}System.out.print("\nusing ByteBuffer: ");buffer.rewind();buffer.put(5,(byte)'X');for(int i = buffer.position(); i < buffer.limit()/2; i++){System.out.print(buffer.getChar() + " ");}}}
In the code above, we create a ByteBuffer called buffer and allocate it with a capacity of bytes. Next, we create a view buffer using the asCharBuffer() method and call it charBuff. This allows us to put values of type char in the buffer.
We use the put() method of the CharBuffer object to write values into the buffer as follows:
charBuff.put()
The for loop in line prints the contents of the byte array using CharBuffer. In this loop, we start from the index given by position() all the way through the index at limit() / 2. We need to divide by because the ByteBuffer is indexed by bytes and each char value takes two bytes of memory.
In line , we put the character X in the buffer using the put() method of the ByteBuffer object instead of the CharBuffer object. However, the changes are also visible in the buffer object.
