Sierpinski square curve: Difference between revisions

}</lang>

=={{header|Java}}==

{{trans|C++}}

<lang java>import java.io.*;

public class SierpinskiSquareCurve implements AutoCloseable {

public static void main(final String[] args) {

try (SierpinskiSquareCurve s = new SierpinskiSquareCurve("sierpinski_square.svg", 635)) {

s.currentAngle = 0;

s.currentX = 315;

s.currentY = 630;

s.lineLength = 5;

s.execute(rewrite(5));

s.end();

} catch (final Exception ex) {

ex.printStackTrace();

}

}

private SierpinskiSquareCurve(final String file, final int size) throws IOException {

writer = new BufferedWriter(new FileWriter(file));

write("<svg xmlns='http://www.w3.org/2000/svg' width='%d' height='%d'>\n", size, size);

write("<rect width='100%%' height='100%%' fill='white'/>\n");

write("<path stroke-width='1' stroke='black' fill='none' d='");

}

public void close() throws IOException {

writer.close();

}

private void end() throws IOException {

write("'/>\n</svg>\n");

}

private void execute(final String s) throws IOException {

write("M%g,%g\n", currentX, currentY);

for (int i = 0, n = s.length(); i < n; ++i) {

switch (s.charAt(i)) {

case 'F':

line(lineLength);

break;

case '+':

turn(-ANGLE);

break;

case '-':

turn(ANGLE);

break;

}

}

}

private void line(final double length) throws IOException {

final double theta = (Math.PI * currentAngle) / 180.0;

currentX += length * Math.cos(theta);

currentY += length * Math.sin(theta);

write("L%g,%g\n", currentX, currentY);

}

private void turn(final int angle) {

currentAngle = (currentAngle + angle) % 360;

}

private void write(final String format, final Object... args) throws IOException {

writer.write(String.format(format, args));

}

private static String rewrite(final int order) {

String s = AXIOM;

for (int i = 0; i < order; ++i) {

final StringBuilder sb = new StringBuilder();

for (int j = 0, n = s.length(); j < n; ++j) {

final char ch = s.charAt(j);

if (ch == 'X')

sb.append(PRODUCTION);

else

sb.append(ch);

}

s = sb.toString();

}

return s;

}

private final Writer writer;

private double lineLength;

private double currentX;

private double currentY;

private int currentAngle;

private static final String AXIOM = "F+XF+F+XF";

private static final String PRODUCTION = "XF-F+F-XF+F+XF-F+F-X";

private static final int ANGLE = 90;