import java.math.BigDecimal;

/**
 * Computes the sum of the series 1 - 1/2 + 1/4 - 1/6 + 1/8 etc. Demonstrates
 * the use of {@link java.math.BigDecimal} in order to achieve high precision
 * floating point numbers. 
 * 
 * @author Tim De Pauw
 */
public class BigDecTest {
	/**
	 * Size of the series.
	 */
	public final static int SIZE = 1000000;
	
	/**
	 * Number of digits to the right of the decimal point.
	 */
	public final static int SCALE = 50;
	
	/**
	 * Auxiliary constant. A {@link java.math.BigDecimal} representing the
	 * number two.
	 */
	public final static BigDecimal TWO = new BigDecimal(2);

	/**
	 * Auxiliary constant. A {@link java.math.BigDecimal} representing the
	 * number one.
	 */
	public final static BigDecimal ONE = new BigDecimal(1);

	/**
	 * Auxiliary constant. A {@link java.math.BigDecimal} representing the
	 * number negative one.
	 */
	public final static BigDecimal NEG_ONE = new BigDecimal(-1);
	
	public static void main (String[] args) {
		System.out.println("Size:   " + SIZE);
		System.out.println("Scale:  " + SCALE);
		BigDecimal sum = ONE;
		long start = System.currentTimeMillis();
		for (int i = 1; i < SIZE; i++)
			sum = sum.add((i % 2 == 0 ? ONE : NEG_ONE)
				.divide(TWO.multiply(new BigDecimal(i)),
					SCALE,
					BigDecimal.ROUND_HALF_UP));
		long end = System.currentTimeMillis();
		System.out.println("Result: " + sum);
		System.out.println("Time:   " + (end - start) / 1000.0 + " seconds");
	}
}