BigIntegers syntax.. How to read in from console program

[sonny]

How to i read in a BigInteger from the console prgram??

The exercise was to rewrite a rational number class using BigIntegers ( the original code which uses ints was provided in my study text and is posted here: trying to understand this rational numbers class

after consulting javadoc and other stuff on google I think i have achieved the goal (at least eclipse shows no compile errors) however i am having a mental block or something, because i cant work out how to test my code because i cannot read in a biginteger.

i have tried various things using scrapbook and a console program . I am assuming that I have to read in a string and convert it to a biginteger.
I arrived at this notion because of entry number 5 in the constructor summary information at javadoc states:

BigInteger(String val)
Translates the decimal String representation of a BigInteger into a BigInteger.

and i am assuming this is the way I must do it,,

it has occured to me however that perhaps my code (despite having no compile errors) is a pile of junk! so ive posted it below.

also there is something about throwing exceptions which i may not have done in the conventional way, i am not concerned with this too much at the moment, but any suggestions on throwing exceptions will be gratefully accepted.

BigRational code:

import java.math.BigInteger;
import acm.util.ErrorException;

public class BigRational { 
	private BigInteger numerator;
	private BigInteger denominator;
	
	
	public BigRational(){
		this(BigInteger.ZERO);
	}
	
	public BigRational(BigInteger numerator){
		this(numerator,BigInteger.ONE);
		
	}
	public BigRational(BigInteger numerator, BigInteger denominator) {
		if (BigInteger.ZERO == denominator)
			throw new ErrorException("Cannot divide by zero.");
		BigInteger gcd = numerator.abs().gcd(denominator.abs());
		this.numerator = numerator.divide(gcd);
		this.denominator = denominator.divide(gcd);
    }

	public BigRational add(BigRational r) {
		return new BigRational
		(this.numerator.multiply(r.denominator)
				.add(r.numerator.multiply(this.denominator)), 
				this.denominator.multiply(r.denominator));
	}

	public BigRational subtract(BigRational r) {
		return new BigRational(this.numerator.multiply(r.denominator)
				.subtract(r.numerator).multiply(this.denominator),
				this.denominator.multiply(r.denominator));
	}

	public BigRational multiply(BigRational r) {
		return new BigRational(this.numerator.multiply(r.numerator), 
				this.denominator.multiply(r.denominator));
	}

	public BigRational divide(BigRational r) {
		return new BigRational(this.numerator.multiply(r.denominator),
				this.denominator.multiply(r.numerator));
	}

	public String toString() {
		if (denominator == BigInteger.ONE) {
			return "" + numerator;
		} else {
			return numerator + "/" + denominator;
		}
	}	

}

[iluxa]

your code looks good.

Instead of throwing ErrorException consider IllegalArgumentException

as far as parsing string into BigInteger, you should indeed be able to use

String str = "123";
new BigInteger (str);

when you're reading from console, one thing to watch out for is un-intended whitespace in your string. So just in case, do this:

// acquire String str somewhere
str = str.trim (); // strips the whitespace
new BigInteger (str);

[sonny]

Thanks mate,
it might have helped if i had imported java.math into my scrapbook :o
perhaps i would have remembered had i not had a few beers! LOL

String num = readLine("  Numerator: ");
num.trim();
String den = readLine("Denominator: ");
den.trim();
BigInteger numerator = new BigInteger(num);
BigInteger denominator = new BigInteger(den);
BigRational one = new BigRational(numerator,denominator);

and now everything seems to work nicely
thanks

[Fubarable]

Thanks mate,
it might have helped if i had imported java.math into my scrapbook :o
perhaps i would have remembered had i not had a few beers! LOL

Or perhaps not enough: Ballmer Peak

Looks like your programming is coming along nicely. Keep it up.

[sonny]

Or perhaps not enough: Ballmer Peak

Looks like your programming is coming along nicely. Keep it up.

many thanks

hopefully its coming along as well as my capacity for beer!

private void gotSomeTime2Kill(int beersInFridge, boolean WifeAndKidsInBed);
	while (beersInFridge > 0 && wifeAndKidsInBed){
		consumeOneBeer();
		beersInFridge--;
		beerConsumed++
		doSomeMoreCode();
		if(beerConsumed > BallmerPeak) postSomeDaftHelpRequest();
		else {
			gotSomeTimeToKill(beersInFridge,(true));
		}
	}