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Java and fractions

I'm trying to add three instance methods to the public interface of class 'Fraction' that all return a 'Fraction' as a result:
add, subtraction and multiplication. is it possible to change it from my current code into instance methods?
I just can't get it to work
Here is my code:
class Fraction {
private Integer numerator;
private Integer denumerator;
public Fraction(Integer numerator, Integer denumerator) {
int gcd = 1;
for (int i = 1; i <= numerator && i <= denumerator; i++) {
if (numerator % i == 0 && denumerator % i == 0)
gcd = i;
}
this.numerator = numerator / gcd;
this.denumerator = denumerator / gcd;
}
public Fraction(Integer numerator) {
this.numerator = numerator;
this.denumerator = 1;
}
public String toString() {
return numerator + "/" + denumerator;
}
public static Fraction add(Fraction f1,Fraction f2){
return new Fraction(f1.numerator*f2.denumerator+f2.numerator*f1.denumerator,f1.denumerator*f2.denumerator);
}
public static Fraction subtract(Fraction f1,Fraction f2){
return new Fraction(f1.numerator*f2.denumerator-f2.numerator*f1.denumerator,f1.denumerator*f2.denumerator);
}
public static Fraction mul(Fraction f1,Fraction f2){
return new Fraction(f1.numerator*f2.numerator,f1.denumerator*f2.denumerator);
}
}
class Main
{
public static void main(String[] arguments)
{
final Fraction HALF = new Fraction(1, 2);
final Fraction THREE_FIFTH = new Fraction(3, 5);
System.out.println(HALF.add(HALF, THREE_FIFTH).toString());
System.out.println(THREE_FIFTH.subtract(HALF, THREE_FIFTH).toString());
System.out.println(HALF.mul(HALF, THREE_FIFTH).toString());
}
}

public static Fraction add(Fraction f1,Fraction f2){
return new Fraction(f1.numerator*f2.denumerator+f2.numerator*f1.denumerator,
f1.denumerator*f2.denumerator);
}
is a class method (because of the static it does not need an instance to call "on").
Making it instance method would look like
public Fraction add(Fraction other){
return new Fraction(this.numerator*other.denumerator+other.numerator*this.denumerator,
this.denumerator*other.denumerator);
}
of course you do not actually need to write the thiss there, just they emphasize that f1 became the current object, and f2 became the single argument.
Then you could use it as
Fraction HALF = new Fraction(1, 2);
Fraction THREE_FIFTH = new Fraction(3, 5);
System.out.println(HALF.add(THREE_FIFTH));
without repeating HALF (like HALF.add(HALF,THREE_FIFTH) in the original code).
Side comment: class methods (static stuff) can be referred via the name of the class, your original code would be more conventionally called in the form Fraction.add(...):
System.out.println(Fraction.add(HALF,THREE_FIFTH));
(System.out.println() knows that it should call toString() so you do not actually need to do that yourself)

Converting double to fraction using BigInteger [duplicate]

This question already has answers here:
How do I print my Java object without getting "SomeType#2f92e0f4"?
(13 answers)
Closed 7 years ago.
I'm learner of Java.
I'm trying to convert decimal to fraction using BigInteger in Rational class.
If I print the numerator and denominator, right output comes out.
However, when I add, subtract, multiply, and divide, some strange output come out.
For example when I inputs
3.25 -3
The output is
13 4
-3 1
RationalTest#14ae5a5
RationalTest#7f31245a
RationalTest#6d6f6e28
RationalTest#135fbaa4
What is wrong with my code? What is that hashcode?
I couldn't find out in the internet, so I need your help:<
import java.util.Scanner;
import java.math.*;
public class TestTest
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
RationalTest r1 = RationalTest.getFraction(sc.next());
RationalTest r2 = RationalTest.getFraction(sc.next());
//Test if the right numerator and denominator comes out
System.out.println(r1.getNumerator()+" "+r1.getDenominator());
System.out.println(r2.getNumerator()+" "+r2.getDenominator());
System.out.println(r1.add(r2));
System.out.println(r1.subtract(r2));
System.out.println(r1.multiply(r2));
System.out.println(r1.divide(r2));
}
}
class RationalTest extends Number implements Comparable<RationalTest>
{
private static final long serialVersionUID = 1L;
private BigInteger numerator = BigInteger.ZERO;
private BigInteger denominator = BigInteger.ONE;
public RationalTest()
{
this(BigInteger.ZERO, BigInteger.ONE);
}
//Find GCD of numerator and denominator
public RationalTest(BigInteger numerator, BigInteger denominator)
{
BigInteger gcd = gcd(numerator, denominator);
this.numerator = ((denominator.compareTo(BigInteger.ZERO)>0) ? new BigInteger("1"):new BigInteger("-1")).multiply(numerator.divide(gcd));
this.denominator = denominator.abs().divide(gcd);
}
//Converting decimal to fraction
public static RationalTest getFraction(String s)
{
int result=-1;
for(int i=0; i<s.length(); i++)
{
if(s.charAt(i)=='.')
{
result=1;
break;
}
else
result=0;
}
//If result=1, String s is a decimal
if(result==1)
{
double d = Double.parseDouble(s);
long num = (long) Math.floor(d); // Only the int part
double denom = d-num; // Only the decimal part
int digitDec = s.length()-1-s.indexOf('.');
long up = (int) (denom*Math.pow(10, digitDec)); // numerator of denom
long down = (int) Math.pow(10, digitDec); // denominator of denim
return new RationalTest(BigInteger.valueOf(down*num+up), BigInteger.valueOf(down));
}
//If result=0, String s is not a decimal
else
{
return new RationalTest(BigInteger.valueOf(Long.parseLong(s)), BigInteger.ONE);
}
}
private static BigInteger gcd(BigInteger n, BigInteger d)
{
BigInteger n1 = n.abs();
BigInteger n2 = d.abs();
BigInteger gcd = BigInteger.ONE;
for(BigInteger k=BigInteger.ONE; k.compareTo(n1)<=0 && k.compareTo(n2)<=0; k=k.add(BigInteger.ONE))
{
if(n1.mod(k).equals(BigInteger.ZERO) && n2.mod(k).equals(BigInteger.ZERO))
gcd = k;
}
return gcd;
}
public BigInteger getNumerator()
{
return numerator;
}
public BigInteger getDenominator()
{
return denominator;
}
public RationalTest add(RationalTest secondRationalTest)
{
BigInteger n = (numerator.multiply(secondRationalTest.getDenominator())).add(denominator.multiply(secondRationalTest.getNumerator()));
BigInteger d = denominator.multiply(secondRationalTest.getDenominator());
return new RationalTest(n, d);
}
public RationalTest subtract(RationalTest secondRationalTest)
{
BigInteger n = (numerator.multiply(secondRationalTest.getDenominator())).subtract(denominator.multiply(secondRationalTest.getNumerator()));
BigInteger d = denominator.multiply(secondRationalTest.getDenominator());
return new RationalTest(n, d);
}
public RationalTest multiply(RationalTest secondRationalTest)
{
BigInteger n = numerator.multiply(secondRationalTest.getNumerator());
BigInteger d = denominator.multiply(secondRationalTest.getDenominator());
return new RationalTest(n, d);
}
public RationalTest divide(RationalTest secondRationalTest)
{
BigInteger n = numerator.multiply(secondRationalTest.getDenominator());
BigInteger d = denominator.multiply(secondRationalTest.getNumerator());
return new RationalTest(n, d);
}
#Override
public boolean equals(Object other)
{
if((this.subtract((RationalTest)(other))).getNumerator().equals(BigInteger.ZERO))
return true;
else
return false;
}
#Override
public int intValue()
{
return (int)doubleValue();
}
#Override
public float floatValue()
{
return (float)doubleValue();
}
#Override
public double doubleValue()
{
double x = this.getNumerator().doubleValue();
double y = this.getDenominator().doubleValue();
return x/y;
}
#Override
public long longValue()
{
return (long)doubleValue();
}
#Override
public int compareTo(RationalTest o) {
if(this.subtract(o).getNumerator().compareTo(BigInteger.ZERO)>0)
return 1;
else if(this.subtract(o).getNumerator().compareTo(BigInteger.ZERO)<0)
return -1;
else
return 0;
}
}

Oh I found out that I have to return string using toString()..
Thanks for your help!

Check repetition of fractions of external file

I'm creating a program that has a requirement of three classes. The program reads an external text file filled with fractions, and is to return how many times each fraction is repeated. 4/2 has to be reduced to 2/1 and is +1 for the 2/1 count. I believe I am almost done, but I cannot figure out what I need to put into my compareAndIncrement() method in my FractionCounter class. It is suppose to be used to see if the newFraction passed into the function is the same as the Fraction being stored, and if so increments the counter by one and returns true (otherwise, returns false). Below are the codes for my classes.
FractionCounter
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class FractionCounter {
private Fraction theFraction;
private int counter = 0;
public FractionCounter(Fraction theFraction ){
}
public boolean compareAndIncrement(Fraction newFraction){
return false;
}
public String toString(){
return "";
}
public static void main(String[] args){
ObjectList num = new ObjectList();
ObjectList den = new ObjectList();
Scanner fractionFile = null;
try{
fractionFile = new Scanner(new FileInputStream("fractions.txt"));
}
catch (FileNotFoundException e){
System.out.println("File not found.");
System.exit(0);
}
while (fractionFile.hasNextLine()){
String[] part = (fractionFile.nextLine().split("/"));
num.add(Integer.parseInt(part[0]));
den.add(Integer.parseInt(part[1]));
}
}
}
Fraction
public class Fraction {
private int numerator;
private int denominator;
public Fraction() {
}
public Fraction(int num, int den) {
setNumerator(num);
setDenominator(den);
}
public void setNumerator(int num) { //sets numerator
numerator = num;
}
public int getNumerator() { //gets numerator
return numerator;
}
public void setDenominator(int den) { //sets denominator
if(den == 0) {
System.out.println("Error: Denominator = 0");
System.exit(0);
} else {
denominator = den;
}
}
public int getDenominator() { //gets denominator
return denominator;
}
public boolean equals(Fraction that) {
return ((double)this.numerator/this.denominator) == ((double)that.numerator/that.denominator);
}
}
ObjectList
public class ObjectList {
private int[] fraction = new int[100];
private int numElements = 0;
public void add(int n){
fraction[numElements] = n;
numElements++;
}
public String toString(){
String retVal = "";
for (int i = 0; i < numElements; i++){
retVal += fraction[i] + ",";
}
return retVal;
}
public int indexOf(int[] input, int target) {
//returns the index of the inputed value
if(contains(input,target) == true){
for(int i = 0;i <= target;i++) {
if(input[i] == target) {
return i;
}
}
}
return -1;
}
public boolean contains(int[] input, int target) {
//is the target in the inputed array?
for(int i=0;i<input.length; i++) {
if(input[i] == target) {
return true;
}
}
return false;
}
}
Any hints or tips for what I need to do to my method would be much appreciated. I can't figure out a way to do it without using numElements and fraction variables from my ObjectList class. Thank you

I would make a Map to make the counter :
private static final Map<Fraction, Integer> counter = new HashMap<Fraction, Integer>();
and for each Fraction element read for the file I would do :
if(counter.containsKey(fraction)){
Integer count = counter.get(fraction);
count++;
counter.put(fraction, count);
} else {
counter.put(fraction, 1);
}
Moreover, I would make a static parse fonction in the Fraction class which return a Fraction instance from the line you just read. And a toString function to print it easely.

Fraction.java Keep getting object address not the values I want

I am working on this program and keep getting this result.
To convert fractional measures,
enter the fractional measure you want to convert: 3/4
Enter the fractional amount to reduce/increase it by: 1/2
The converted measurement is: Fraction#6750cf54
The part is bold is the problem.
This is my main program.
import java.util.*; // Scanner
import java.io.*; // PrintStream
public class Pierre1 extends Object
{
public static void main(String args[])
{
PrintStream theScreen = new PrintStream(System.out);
Scanner theKeyboard = new Scanner(System.in);
theScreen.println("\nTo convert fractional measures,");
theScreen.print(" enter the fractional measure you want to convert: ");
Fraction oldMeasure = new Fraction();
oldMeasure.read(theKeyboard);
theScreen.print("\nEnter the fractional amount to reduce/increase it by: ");
Fraction scaleFactor = new Fraction(1,6);
scaleFactor.read(theKeyboard);
Fraction newMeasure = oldMeasure.times(scaleFactor);
theScreen.print("\nThe converted measurement is: ");
theScreen.print(newMeasure);
theScreen.println();
theScreen.println();
}
}
This is my other program.
import java.util.*; // Scanner
import java.io.*; // PrintStream
public class Fraction extends Object
{
private int myNumerator = 0;
private int myDenominator = 0;
public void print(PrintStream out)
{
System.out.print(myNumerator + "/" + myDenominator);
}
public Fraction()
{
myNumerator = 0;
myDenominator = 1;
}
public Fraction(int numerator, int denominator)
{
myNumerator = numerator;
myDenominator = denominator;
}
private int numerator()
{
return myNumerator;
}
private int denominator()
{
return myDenominator;
}
public void read (Scanner in)
{
String fraction = in.next();
StringTokenizer parser = new StringTokenizer(fraction, "/", false);
if (parser.countTokens() != 2)
throw new RuntimeException("Bad Fraction Format");
myNumerator = Integer.parseInt(parser.nextToken());
myDenominator = Integer.parseInt(parser.nextToken());
}
Fraction times(Fraction rightOperand)
{
Fraction result
= new Fraction(myNumerator*rightOperand.numerator(),
myDenominator*rightOperand.denominator());
result.simplify(result);
return result;
}
public Fraction simplify(Fraction getGcd)
{
Fraction result = new Fraction();
int num = numerator();
int den = denominator();
int gcd = greatestCommonDivisor(num, den);
if (gcd == 0)
return result;
else
{
myNumerator = myNumerator / gcd;
myDenominator = myDenominator / gcd;
}
return result;
}
private static int greatestCommonDivisor(int alpha, int beta)
{
alpha = Math.abs(alpha); // take absolute values of operands
beta = Math.abs(beta);
if (beta == 0) // base case
return alpha;
else // induction step
{
int remainder = alpha % beta;
return greatestCommonDivisor(beta, remainder);
}
}
}
What do I need to do to fix this?
I have been scanning the programs to find the problem, but my limited java experience is getting the best of me. Any help is greatly appreciated. Thanks in advance!

have a look at the Fraction class that I use (it fixes some of your flaws: numerator and denumerator should be final, etc.)
// code by jph
package sys.mat;
/** non degenerate integer fraction in normal form */
public class Fraction implements Comparable<Fraction> {
/** numerator */
public final int num;
/** denominator (always greater than zero) */
public final int den;
public static int gcd(int a, int b) {
if (b == 0)
return a;
return gcd(b, a % b);
}
/** #param num
* #param den has to be non-zero
* #throws {#link ArithmeticException} if den is zero */
public Fraction(final int num, final int den) {
int gcd = gcd(num, den);
int res = den / gcd;
if (0 < res) {
this.num = num / gcd;
this.den = res;
} else {
this.num = -num / gcd;
this.den = -res;
}
}
public Fraction add(Fraction myFraction) {
return new Fraction(num * myFraction.den + den * myFraction.num, den * myFraction.den);
}
public Fraction sub(Fraction myFraction) {
return new Fraction(num * myFraction.den - den * myFraction.num, den * myFraction.den);
}
public Fraction mul(Fraction myFraction) {
return new Fraction(num * myFraction.num, den * myFraction.den);
}
public Fraction mul(int myInt) {
return new Fraction(num * myInt, den);
}
public Fraction div(Fraction myFraction) {
return new Fraction(num * myFraction.den, den * myFraction.num);
}
/** also denoted reciprocal
*
* #return den/num */
public Fraction inverse() {
return new Fraction(den, num);
}
/** #return true if den == 1 */
public boolean isInteger() {
return den == 1;
}
public double toDouble() {
return num / (double) den;
}
/** may only be called if isInteger() returns true
*
* #return num */
public int toInteger() {
if (!isInteger()) // assert den == 1
throw new RuntimeException(toString() + " is no integer");
return num;
}
#Override
public int compareTo(Fraction myFraction) {
// return num * myFraction.den - den * myFraction.num; // does not work for big integers
return Double.compare(toDouble(), myFraction.toDouble());
}
public boolean equalsInteger(int value) {
return equals(new Fraction(value, 1));
}
#Override
public boolean equals(Object myObject) {
if (myObject == null) // || !(myObject instanceof Fraction)
return false;
Fraction myFraction = (Fraction) myObject;
return num == myFraction.num && den == myFraction.den; // sufficient since in normal form
}
#Override
public int hashCode() {
// n / 1 is mapped to n, thus is identical to getInteger()
return num + den - 1;
}
#Override
public String toString() {
return num + "/" + den;
}
}

Why aren't the values of these variables being set properly by the methods getFraction1 and getFraction2?

I have tried to write TestFraction in such a way that the main method calls on the methods getFraction1 and getFraction2 to create two Fractions: fr1 (a/b) and fr2 (a/b). getFraction1 and getFraction2 prompt the user for two integers, a and b, and call on getNumber to capture these integers. Fraction then performs calculations on fr1 and fr2. The problem is, when I run TestFraction, the values of a and b are left at 1, which is what they're set to in Fraction. Can anyone give me a hint as to why getFraction1 and getFraction2 aren't actually passing the values of a and b into fr1 and fr2?
Here is my code for TestFraction:
package Fraction;
import java.io.*;
import java.util.*;
public class TestFraction
{
static Scanner console = new Scanner (System.in);
private static int getNumber() throws InputMismatchException
{
return console.nextInt();
}
private static Fraction getFraction1()
{
int a=1, b=1;
Fraction frac = new Fraction ();
while (true) {
// prompt to enter a numerator and a denominator
System.out.println("Input 1st fraction numerator and denominator");
// input the numerator and the denominator using getNumber()
try {
a = getNumber();
b = getNumber();
}
catch (Exception e)
{
System.out.println("Exception: "+e.toString());
console.nextLine();
continue;
}
return frac;
// return new Fraction if OK
// otherwise print an error message
}
}
private static Fraction getFraction2()
{
int a=1, b=1;
Fraction frac = new Fraction ();
while (true) {
// prompt to enter a numerator and a denominator
System.out.println("Input 2nd fraction numerator and denominator");
// input the numerator and the denominator using getNumber()
try {
a = getNumber();
b = getNumber();
}
catch (Exception e)
{
System.out.println("Exception: "+e.toString());
console.nextLine();
continue;
}
return frac;
// return new Fraction if OK
// otherwise print an error message
}
}
public static void main(String[] args)
{
Fraction fr1 = new Fraction ();
fr1 = getFraction1();
Fraction fr2 = new Fraction ();
fr2 = getFraction2();
Fraction res = new Fraction();
// define other variables including res and fr2
res = Fraction.add (fr1, fr2);
System.out.println(fr1+" + "+fr2+" = "+res);
res = Fraction.subtract (fr1, fr2);
System.out.println(fr1+" - "+fr2+" = "+res);
res = Fraction.multiply (fr1, fr2);
System.out.println(fr1+" * "+fr2+" = "+res);
res = Fraction.divide (fr1, fr2);
System.out.println(fr1+" / "+fr2+" = "+res);
res = Fraction.lessThan (fr1, fr2);
System.out.println(fr1+" "+res+" "+fr2);
// test subtract, multiply, divide, lessThan methods
// each test has to print a description, a result,
// and, possibly, a error message if the calculation fails
}
}
And here is Fraction:
package Fraction;
public class Fraction
{
protected int a;
protected int b;
public Fraction()
{
a = 1;
b = 1;
}
public Fraction (int a, int b)
{
this.a=a;
this.b=b;
}
public int getNumerator()
{
return a;
}
public int getDenominator()
{
return b;
}
public void setNumerator(int a)
{
this.a=a;
}
public void setDenominator(int b)
{
this.b=b;
}
public String toString ()
{
return a+"/"+b;
}
public int gcd(int a, int b)
{
//ToDo implement Euclide algorithm
if (b==0) return a;
return gcd(b, a%b);
}
public void lowestTerms()
{
int g=gcd(a,b);
a=a/g;
b=b/g;
}
public static Fraction add(Fraction first, Fraction second)
{
Fraction result = new Fraction();
result.setNumerator(first.getNumerator()*second.getDenominator()
+ first.getDenominator()*second.getNumerator());
result.setDenominator(first.getDenominator()*second.getDenominator());
result.lowestTerms();
return result;
}
//ToDo methods subtract, multiply, divide, lessThan
public static Fraction subtract(Fraction first, Fraction second)
{
Fraction result = new Fraction();
result.setNumerator(first.getNumerator()*second.getDenominator()
- first.getDenominator()*second.getNumerator());
result.setDenominator(first.getDenominator()*second.getDenominator());
result.lowestTerms();
return result;
}
public static Fraction multiply(Fraction first, Fraction second)
{
Fraction result = new Fraction();
result.setNumerator(first.getNumerator()*second.getNumerator());
result.setDenominator(first.getDenominator()*second.getDenominator());
result.lowestTerms();
return result;
}
public static Fraction divide(Fraction first, Fraction second)
{
Fraction result = new Fraction();
result.setNumerator(first.getNumerator()*second.getDenominator());
result.setDenominator(first.getDenominator()*second.getNumerator());
result.lowestTerms();
return result;
}
public static Fraction lessThan(Fraction first, Fraction second)
{
if (first.getNumerator()*second.getDenominator() <=
first.getDenominator()*second.getNumerator()){
return first;
}
else {
return second;
}
}
}

You must use the Faction(int, int) constructor instead of Fraction() constructor:
Fraction frac = new Fraction ();
must be
Fraction frac = null;
//later in the code once you have a and b variables set and no exceptions...
frac = new Fraction (a, b);
OR use the setters:
frac.setNumerator(a);
frac.setDenominator(b);
before returning frac variable.

Looks like you are not setting the values you read from the console
a = getNumber();
b = getNumber();
frac.setNumerator(a);
frac.setDenominator(b);
by default a and b are set to 1, when you say
Fraction frac = new Fraction();
because the Fraction default constructor is defined like this
public Fraction()
{
a = 1;
b = 1;
}