CharBuffer vs. char[]

Question

Is there any reason to prefer a CharBuffer to a char[] in the following:

CharBuffer buf = CharBuffer.allocate(DEFAULT_BUFFER_SIZE); while( in.read(buf) >= 0 ) {   out.append( buf.flip() );   buf.clear(); } 

vs.

char[] buf = new char[DEFAULT_BUFFER_SIZE]; int n; while( (n = in.read(buf)) >= 0 ) {   out.write( buf, 0, n ); } 

(where in is a Reader and out in a Writer)?

Answer 1

No, there's really no reason to prefer a CharBuffer in this case.

In general, though, CharBuffer (and ByteBuffer) can really simplify APIs and encourage correct processing. If you were designing a public API, it's definitely worth considering a buffer-oriented API.

Answer 2

I wanted to mini-benchmark this comparison.

Below is the class I have written.

The thing is I can't believe that the CharBuffer performed so badly. What have I got wrong?

EDIT: Since the 11th comment below I have edited the code and the output time, better performance all round but still a significant difference in times. I also tried out2.append((CharBuffer)buff.flip()) option mentioned in the comments but it was much slower than the write option used in the code below.

Results: (time in ms)
char[] : 3411
CharBuffer: 5653

public class CharBufferScratchBox {     public static void main(String[] args) throws Exception     {         // Some Setup Stuff         String smallString =                 "1111111111222222222233333333334444444444555555555566666666667777777777888888888899999999990000000000";          StringBuilder stringBuilder = new StringBuilder();         for (int i = 0; i < 1000; i++)         {             stringBuilder.append(smallString);         }         String string = stringBuilder.toString();         int DEFAULT_BUFFER_SIZE = 1000;         int ITTERATIONS = 10000;          // char[]         StringReader in1 = null;         StringWriter out1 = null;         Date start = new Date();         for (int i = 0; i < ITTERATIONS; i++)         {             in1 = new StringReader(string);             out1 = new StringWriter(string.length());              char[] buf = new char[DEFAULT_BUFFER_SIZE];             int n;             while ((n = in1.read(buf)) >= 0)             {                 out1.write(                         buf,                         0,                         n);             }         }         Date done = new Date();         System.out.println("char[]    : " + (done.getTime() - start.getTime()));          // CharBuffer         StringReader in2 = null;         StringWriter out2 = null;         start = new Date();         CharBuffer buff = CharBuffer.allocate(DEFAULT_BUFFER_SIZE);         for (int i = 0; i < ITTERATIONS; i++)         {             in2 = new StringReader(string);             out2 = new StringWriter(string.length());             int n;             while ((n = in2.read(buff)) >= 0)             {                 out2.write(                         buff.array(),                         0,                         n);                 buff.clear();             }         }         done = new Date();         System.out.println("CharBuffer: " + (done.getTime() - start.getTime()));     } }