/*  Mock test Lab on 17-09-2008 Wednesday
 *  Write a JAVA program to convert a number given in decimal number representation to
 *	its equivalent binary number representation and print the binary value. For example, if
 *	the input is 25, then the output should be 11001 (which is the binary representation of
 *	2510 ). Similarly, if the input is −11 then the output should be −1011 (which is the binary
 *	representation of −1110 ). Your program has to work for all values of integer n whose binary
 *	representation has 10 digits only. You must take the input as command-line argument.
 */
public class DecimalToBinary {

	public static void main(String[] args) {
		//Checking for the number of command line arguments
		if(args.length !=1 ) {
				System.out.println("Please supply a integer arguement with the program...");
				return;
		}
		
		int decimalNumber , binaryEquivalent;
		
		//Parsing the number given in command line
		try {
			decimalNumber = Integer.parseInt(args[0]);
		}
		catch(NumberFormatException ex) {
			System.out.println("The supplied arguemt cannot be parsed as integer...");
			return;
		} //Making sure that the command line argument passed is an integer else terminate with message
		
		//Decimal number >= 1024 will require more than 10 bits in binary equivalent so are the decimal numbers <= -1024
		if(decimalNumber >= 1024 || decimalNumber <= -1024) {
			System.out.println("Binary representation of " + decimalNumber + " will take more than 10 bits...");
			return;
		}
		
		//If decimalNumber is positive the we pass the number directly to returnBinaryEquivalent
		if(decimalNumber >= 0) {
			binaryEquivalent = returnBinaryEquivalent(decimalNumber);
			System.out.println(binaryEquivalent);
		}
		
		//else we pass the absolute value and print the binary equivalent of the absolute value appended by a negation
		else {
			binaryEquivalent = returnBinaryEquivalent(-decimalNumber);
			System.out.println("-"+binaryEquivalent);
		}
		

	}

	//Function returning the binary equivalent of +ve decimal integers
	public static int returnBinaryEquivalent(int decimalNumber) {
		int binaryNumber = 0, counter = 1;
		//Every time we get a decimalNumber%2 we append it as MSB of the binaryNumber. We use a counter for it to track the position of MSB
		while(decimalNumber != 0) {
			binaryNumber = binaryNumber + (decimalNumber%2) * counter;
			counter *= 10;
			decimalNumber /= 2;
		}
		return binaryNumber;
	}

}