Solution to Daily Programmer challenge #246

XMassLights.java

package challenge246;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Scanner;

public class XMassLights {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		System.out.println("Numbers in brackets are examples");
		// LED Values
		System.out.println("Enter LED voltage: (1.7)");
		double ledVoltage = sc.nextDouble();
		System.out.println("Enter LED current in mA: (20)");
		int ledCurrent_mA = sc.nextInt();
		int maxLEDs;

		// Battery values.
		System.out.println("Enter battery voltage: (9)");
		int batteryVoltage = sc.nextInt();
		System.out.println("Enter battery capacity in mAh: (1200)");
		int batteryCapacity_mAh = sc.nextInt();

		// Time
		System.out.println("Enter duration in hours: (20)");
		int time = sc.nextInt();

		// Calculate amount of LEDs in series.
		double tmp = batteryVoltage / ledVoltage;
		int ledsInSeries = (int) tmp;

		// Current
		int current_mA;
		double current_A;

		// Regarding resistance
		double resistance;
		double totalLEDVoltage = ledVoltage * ledsInSeries;
		double resistorVolatage = batteryVoltage - totalLEDVoltage;

		/* Part 1: Max amount of lights */
		System.out.println("\r\nPart 1: Max amount of lights.");
		System.out.println("Enter duration in hours: (1)");
		current_mA = batteryCapacity_mAh / time;

		maxLEDs = (current_mA / ledCurrent_mA) * ledsInSeries;

		System.out.println("Max number of LEDs: " + maxLEDs + "\r\n");

		/* Part 2: Drawing circuit */
		System.out.println("Part 2: Drawing circuit.");
		int numLEDs = maxLEDs;
		int numLEDsLeft = numLEDs;
		int t;

		System.out.print("*");
		while (numLEDsLeft > 1) {

			if (numLEDsLeft >= ledsInSeries)
				t = ledsInSeries;
			else
				t = numLEDsLeft;

			// Printing LEDs.
			for (int i = 0; i < t; i++) {
				System.out.print("-" + "-|>|-" + "-");
				numLEDsLeft--;
			}
			// Printing end asterix
			if (numLEDsLeft == numLEDs - ledsInSeries)
				System.out.print("*");

			// Printing first LED joiner
			if (numLEDsLeft > 0)
				System.out.print("\n |");

			// Printing spaces
			for (int i = 0; i < ledsInSeries; i++) {
				System.out.print("      ");
			}

			// Printing end LED joiner
			if (numLEDsLeft > 0)
				System.out.print(" |\n");
		}

		/* Part 3: Resistors */
		System.out.println("\r\n");
		System.out.println("Part 3: Resistors");

		current_mA = batteryCapacity_mAh / time;
		current_A = (double) current_mA / 1000;
		resistance = resistorVolatage / current_A;
		
		resistance = XMassLights.round(resistance, 3);

		System.out.println("Resistance: " + resistance + " Ohms");
	}

	public static double round(double value, int places) {
		BigDecimal bd = new BigDecimal(value);
		bd = bd.setScale(places, RoundingMode.HALF_UP);
		return bd.doubleValue();
	}

}