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import java.io.IOException;
/**
* A class for generateing <i>counterstring</i>s.
*
* @author Jin Kwon &lt;onacit_at_gmail.com&gt;
* @see <a href="http://www.satisfice.com/blog/archives/22">Counterstrings: Self-Describing Test Data</a>
*/
public class CounterString {
/**
* Generates a <i>counterstring</i> of specified length by appending characters to given appendable.
*
* @param appendable the appendable into which generated characters are appended.
* @param length the length of the <i>counterstring</i>.
* @param radix a radix for numeric characters.
* @param <T> appendable type parameter.
* @return given appendable.
* @throws IOException if an I/O error occurs.
* @see Integer#toString(int, int)
*/
public static <T extends Appendable> T generate(final T appendable, final int length, final int radix)
throws IOException {
if (appendable == null) {
throw new NullPointerException("appendable is null");
}
if (length < 0) {
throw new IllegalArgumentException("length(" + length + ") < 0");
}
int l = 0;
for (int c = 0; l < length; c++) {
final String s = Integer.toString(c, radix);
if (l + s.length() == c - 1) {
if (l + s.length() + 1 > length) {
appendable.append(s, 0, length - l);
break;
}
appendable.append(s);
l += s.length();
appendable.append('*');
l++;
}
}
return appendable;
}
/**
* The main class of this program whose first argument is the {@code length} and the second optional argument is a
* {@code radix}.
*
* @param args command line argument.
* @throws IOException if an I/O error occurs.
*/
public static void main(final String... args) throws IOException {
final int length = Integer.parseInt(args[0]);
int radix = 10;
try {
radix = Integer.parseInt(args[1]);
} catch (final ArrayIndexOutOfBoundsException aioobe) {
}
final StringBuilder appendable = generate(new StringBuilder(length), length, radix);
assert appendable.length() == length;
System.out.println(appendable.toString());
}
}
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