Re: char addition

From:
"John B. Matthews" <nospam@nospam.invalid>
Newsgroups:
comp.lang.java.help
Date:
Sat, 11 Jul 2009 22:33:07 -0400
Message-ID:
<nospam-AAC962.22330711072009@news.aioe.org>
In article <h3b518$h38$1@inews.gazeta.pl>,
 Piotr Kobzda <pikob@gazeta.pl> wrote:

Dominic wrote:

thank you all very much, that was a great help and I decided to do
this:

public static String makeString(char... word) {
  StringBuilder work = new StringBuilder(word.length);
  for (char chr : word){
    work.append(chr);
  }
  return work.toString().trim();
}


Use of StringBuilder is pointless here. The same effect you may
achieve with:

public static String makeString(char... word) {
   return String.valueOf(word).trim();
}


If makeString() were to be called frequently or with large arrays, the
latter is also appreciably faster:

<console>
Warmup: 8.458 ms.

Size: 10
Builder: 6.383 ms.
ValueOf: 2.269 ms.

Size: 20
Builder: 7.861 ms.
ValueOf: 1.712 ms.

Size: 30
Builder: 9.517 ms.
ValueOf: 1.729 ms.

Size: 40
Builder: 12.208 ms.
ValueOf: 2.113 ms.

Size: 50
Builder: 14.675 ms.
ValueOf: 2.45 ms.
</console>

<code>
import java.util.Random;

/** @author JBM*/
public class MakeStringTest {

    private static final Random random = new Random();

    public static void main(String[] args) {
        (new Warmup()).test(testArray(10));
        System.out.println();
        for (int i = 1; i < 6; i++) {
            int size = i * 10;
            System.out.println("Size: " + size);
            char[] a = testArray(size);
            (new Builder()).test(a);
            (new ValueOf()).test(a);
            System.out.println();
        }
    }

    private static char[] testArray(int count) {
        char[] chars = new char[count];
        for (int i = 0; i < count; i++) {
            chars[i] = (char) (random.nextInt(95) + ' ');
        }
        return chars;
    }
}

abstract class MSTest {

    public static final int COUNT = 20000;

    public void test(char[] word) {
        long start = System.nanoTime();
        for (int i = 0; i < COUNT; i++) {
            makeString(word);
        }
        System.out.println(name()
            + ((float)(System.nanoTime() - start) / 1000000)
            + " ms.");
    }

    public abstract String makeString(char[] in);

    public abstract String name();
}

class Warmup extends MSTest {

    public String makeString(char[] word) {
        StringBuilder work = new StringBuilder(word.length);
        for (char chr : word) {
            work.append(chr);
        }
        return String.valueOf(word);
    }

    public String name() {
        return "Warmup: ";
    }
}

class Builder extends MSTest {

    public String makeString(char[] word) {
        StringBuilder work = new StringBuilder(word.length);
        for (char chr : word) {
            work.append(chr);
        }
        return work.toString().trim();
    }

    public String name() {
        return "Builder: ";
    }
}

class ValueOf extends MSTest {

    public String makeString(char[] word) {
        return String.valueOf(word).trim();
    }

    public String name() {
        return "ValueOf: ";
    }
}
</code>

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>

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