Name: bk70084 Date: 11/06/97


String used to have a method called:

    public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin);

This method is now obsolete because it doesn't take into
consideration the new CharToByte converters. The new
method

    getBytes()

is very inefficient for a number of reasons:

    (1) it dynamically looks up the default CharToByte converter
        *every time* it is invoked. The default convert needs to
        be cached.

    (2) it allocates a byte array, rather than allowing the user
        to specify a destination byte array in which to store the
        coverted bytes.

Turns out that the code to look up CharToByte converts is very
inefficient as well. It performs:

(1) a hash table look up to see if there is an alias for the
    converter
(2) a Class.forName of the resulting class name, after doing a
    couple of String appends
(3) a Class.newInstance of the result

This wouldn't be so bad if the default converter were somehow
cached, or if class String had a method for getBytes which took
a convert as an argument. Unfortunately, the only method in
String which takes a converter argument takes the name of a convert
rather than an instance of one. Perhaps this is because the
converter code is in the sun.* packages rather than JDK, which means
Java Developers shouldn't depend on their existance?

My suggestion is to

(1) Cache an INSTANCE of the default converter, and use the
    clone() method to make new copies of it.
(2) Consider adding back the capability to String of passing
    in the destination byte array. If it turns out that the
    chars expand to more room than is allowed in the byte array,
    then throw an exception, OR, just return the number of bytes
    that successfully fit.

The reason for this suggestion is that I have found that it is
MUCH faster (10 times faster, actually) to use:

    for (int i = 0; i < length; i++) {
        buf[off++] = (byte) string.charAt(i);
    }

than it is to use the getBytes() method of String, even though
the getBytes method was originally created to make the above
the above for loop unnecessary.

Thanks for listening!
(Review ID: 19136)
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