大家好我正在用Java编写一个分数程序。当我运行程序时，我得到以下错误。
Exception in thread "main" java.lang.ArithmeticException
at PJ1.Fraction.setFraction(Fraction.java:63)
at PJ1.Fraction.<init>(Fraction.java:55)
at PJ1.Fraction.add(Fraction.java:89)
at PJ1.Fraction.main(Fraction.java:238)
我不确定错误发生的位置/原因。
package PJ1;
public class Fraction implements FractionInterface, Comparable<Fraction>
{
private int numerator;
private int denominator;
public Fraction()
{
// set fraction to default = 0/1
setFraction(0,1);
} // end default constructor
public Fraction(int num, int den)
{
// implement this method!
setFraction(num,den);
} // end constructor
public void setFraction(int num, int den)
{
// implement this method!
// return FractionException if initial Denominator is 0
if(den==0)
throw new ArithmeticException();
if(den<0){
if(num<0){
den *=-1;
num *=-1;
}
else{
den*=-1;
num*=-1;
}
}
} // end setFraction
public double toDouble()
{
// return double floating point value
// implement this method!
return (double) numerator / denominator;
} // end toDouble
public FractionInterface add(FractionInterface aFraction)
{
// return a new Fraction object
// a/b + c/d is (ad + cb)/(bd)
// implement this method!
Fraction z = new Fraction((numerator *((Fraction)aFraction).denominator) +
(denominator *((Fraction)aFraction).numerator),
denominator * ((Fraction)aFraction).denominator);
z.reduceFractionToLowestTerms();
return z;
} // end add
public FractionInterface subtract(FractionInterface aFraction)
{
// return a new Fraction object
// a/b - c/d is (ad - cb)/(bd)
// implement this method!
Fraction z = new Fraction((numerator *((Fraction)aFraction).denominator) -
(denominator *((Fraction)aFraction).numerator),
denominator * ((Fraction)aFraction).denominator);
z.reduceFractionToLowestTerms();
return z;
} // end subtract
public FractionInterface multiply(FractionInterface aFraction)
{
// return a new Fraction object
// a/b * c/d is (ac)/(bd)
// implement this method!
Fraction z = new Fraction((numerator *((Fraction)aFraction).denominator) *
(denominator *((Fraction)aFraction).numerator),
denominator * ((Fraction)aFraction).denominator);
z.reduceFractionToLowestTerms();
return z;
} // end multiply
public FractionInterface divide(FractionInterface aFraction)
{
// return a new Fraction object
// return FractionException if aFraction is 0
// a/b / c/d is (ad)/(bc)
// implement this method!
Fraction z = new Fraction((numerator *((Fraction)aFraction).denominator) /
(denominator *((Fraction)aFraction).numerator),
denominator * ((Fraction)aFraction).denominator);
z.reduceFractionToLowestTerms();
return z;
} // end divide
public FractionInterface getReciprocal()
{
// return a new Fraction object
// return FractionException if new Fraction is 0
// implement this method!
if(numerator ==0)
throw new ArithmeticException();
return new Fraction(denominator, numerator);
} // end getReciprocal
public boolean equals(Object other)
{
// implement this method!
((Fraction)other).reduceFractionToLowestTerms();
return (numerator == ((Fraction)other).numerator) && (denominator == ((Fraction)other).denominator);
} // end equals
public int compareTo(Fraction other)
{
// implement this method!
if(toDouble() > other.toDouble()){
return 2;
}
else if(toDouble() < other.toDouble()){
return -2;
}
else{
return 0;
} }
// end compareTo
public String toString()
{
return numerator + "/" + denominator;
} // end toString
下面列出了我不应该修改的其他代码。
private void reduceFractionToLowestTerms()
{
// implement this method!
//
// Outline:
// compute GCD of numerator & denominator
// GCD works for + numeratorbers.
// So, you should eliminate - sign
// then reduce numeratorbers : numerator/GCD and denominator/GCD
boolean neg = false;
if(numerator== -1){
numerator *= -1;
neg = true;
}
int gcd = GCD(Math.abs(numerator), Math.abs(denominator));
numerator = numerator / gcd;
denominator = denominator / gcd;
if(neg==true){
numerator *=-1;
}
} // end reduceFractionToLowestTerms
/** Task: Computes the greatest common divisor of two integers.
* @param integerOne an integer
* @param integerTwo another integer
* @return the greatest common divisor of the two integers */
private int GCD(int integerOne, int integerTwo)
{
int result;
if (integerOne % integerTwo == 0)
result = integerTwo;
else
result = GCD(integerTwo, integerOne % integerTwo);
return result;
} // end GCD
//-----------------------------------------------------------------
// Simple test is provided here
public static void main(String[] args)
{
FractionInterface firstOperand = null;
FractionInterface secondOperand = null;
FractionInterface result = null;
double doubleResult = 0.0;
Fraction nineSixteenths = new Fraction(9, 16); // 9/16
Fraction oneFourth = new Fraction(1, 4); // 1/4
System.out.println("\n=========================================\n");
// 7/8 + 9/16
firstOperand = new Fraction(7, 8);
result = firstOperand.add(nineSixteenths);
System.out.println("The sum of " + firstOperand + " and " +
nineSixteenths + " is \t\t" + result);
System.out.println("\tExpected result :\t\t23/16\n");
// 9/16 - 7/8
firstOperand = nineSixteenths;
secondOperand = new Fraction(7, 8);
result = firstOperand.subtract(secondOperand);
System.out.println("The difference of " + firstOperand +
" and " + secondOperand + " is \t" + result);
System.out.println("\tExpected result :\t\t-5/16\n");
// 15/-2 * 1/4
firstOperand = new Fraction(15, -2);
result = firstOperand.multiply(oneFourth);
System.out.println("The product of " + firstOperand +
" and " + oneFourth + " is \t" + result);
System.out.println("\tExpected result :\t\t-15/8\n");
// (-21/2) / (3/7)
firstOperand = new Fraction(-21, 2);
secondOperand= new Fraction(3, 7);
result = firstOperand.divide(secondOperand);
System.out.println("The quotient of " + firstOperand +
" and " + secondOperand + " is \t" + result);
System.out.println("\tExpected result :\t\t-49/2\n");
// -21/2 + 7/8
firstOperand = new Fraction(-21, 2);
secondOperand= new Fraction(7, 8);
result = firstOperand.add(secondOperand);
System.out.println("The sum of " + firstOperand +
" and " + secondOperand + " is \t\t" + result);
System.out.println("\tExpected result :\t\t-77/8\n");
// 0/10, 5/(-15), (-22)/7
firstOperand = new Fraction(0, 10);
doubleResult = firstOperand.toDouble();
System.out.println("The double floating point value of " + firstOperand + " is \t" + doubleResult);
System.out.println("\tExpected result \t\t\t0.0\n");
firstOperand = new Fraction(1, -3);
doubleResult = firstOperand.toDouble();
System.out.println("The double floating point value of " + firstOperand + " is \t" + doubleResult);
System.out.println("\tExpected result \t\t\t-0.333333333...\n");
firstOperand = new Fraction(-22, 7);
doubleResult = firstOperand.toDouble();
System.out.println("The double floating point value of " + firstOperand + " is \t" + doubleResult);
System.out.println("\tExpected result \t\t\t-3.142857142857143");
System.out.println("\n=========================================\n");
firstOperand = new Fraction(-21, 2);
System.out.println("First = " + firstOperand);
// equality check
System.out.println("check First equals First: ");
if (firstOperand.equals(firstOperand))
System.out.println("Identity of fractions OK");
else
System.out.println("ERROR in identity of fractions");
secondOperand = new Fraction(-42, 4);
System.out.println("\nSecond = " + secondOperand);
System.out.println("check First equals Second: ");
if (firstOperand.equals(secondOperand))
System.out.println("Equality of fractions OK");
else
System.out.println("ERROR in equality of fractions");
// comparison check
Fraction first = (Fraction)firstOperand;
Fraction second = (Fraction)secondOperand;
System.out.println("\ncheck First compareTo Second: ");
if (first.compareTo(second) == 0)
System.out.println("Fractions == operator OK");
else
System.out.println("ERROR in fractions == operator");
second = new Fraction(7, 8);
System.out.println("\nSecond = " + second);
System.out.println("check First compareTo Second: ");
if (first.compareTo(second) < 0)
System.out.println("Fractions < operator OK");
else
System.out.println("ERROR in fractions < operator");
System.out.println("\ncheck Second compareTo First: ");
if (second.compareTo(first) > 0)
System.out.println("Fractions > operator OK");
else
System.out.println("ERROR in fractions > operator");
System.out.println("\n=========================================");
System.out.println("\ncheck FractionException: 1/0");
try {
Fraction a1 = new Fraction(1, 0);
System.out.println("Error! No FractionException");
}
catch ( FractionException fe )
{
System.err.printf( "Exception: %s\n", fe );
} // end catch
System.out.println("Expected result : FractionException!\n");
System.out.println("\ncheck FractionException: division");
try {
Fraction a2 = new Fraction();
Fraction a3 = new Fraction(1, 2);
a3.divide(a2);
System.out.println("Error! No FractionException");
}
catch ( FractionException fe )
{
System.err.printf( "Exception: %s\n", fe );
} // end catch
System.out.println("Expected result : FractionException!\n");
} // end main
} // end Fraction
These are the following parts that I am given but I am not supposed to Modify.
/************************************************************************************
* Do not modify this file.
* FractionException class. It is used by Fraction class
*************************************************************************************/
package PJ1;
public class FractionException extends RuntimeException
{
public FractionException()
{
this("");
}
public FractionException(String errorMsg)
{
super(errorMsg);
}
}
* This file specifies methods for FractionInterface */
/* Do not modify this file!! */
package PJ1;
public interface FractionInterface
{
/** Task: Sets a fraction to a given value.
* @param num is the integer numerator
* @param den is the integer denominator
* @throws ArithmeticException if denominator is 0 */
public void setFraction(int num, int den);
/** Task: convert a fraction to double value
* @return the double floating point value of a fraction */
public double toDouble();
/** Task: Adds two fractions.
* @param aFraction is a fraction that is the second operand of the addition
* @return a fraction which is the sum of the invoking fraction and the aFraction */
public FractionInterface add(FractionInterface aFraction);
/** Task: Subtracts two fractions.
* @param aFraction a fraction that is the second operand of the subtraction
* @return a fraction which is the difference of the invoking fraction and the second operand */
public FractionInterface subtract(FractionInterface aFraction);
/** Task: Multiplies two fractions.
* @param aFraction a fraction that is the second operand of the multiplication
* @return a fraction which is the product of the invoking fraction and the aFraction*/
public FractionInterface multiply(FractionInterface aFraction);
/** Task: Divides two fractions.
* @param aFraction a fraction that is the second operand of the division
* @return a fraction which the quotient of the invoking fraction and the aFraction
* @throws FractionException if aFraction is 0 */
public FractionInterface divide(FractionInterface aFraction);
/** Task: Get's the fraction's reciprocal
* @return the reciprocal of the invoking fraction
* @throws FractionException if the new number with denominator is 0*/
public FractionInterface getReciprocal();
}
答案 0 :(得分：0)
我不确定错误发生的位置/原因。
当你的堆栈跟踪告诉它时，
在Fraction.java的第63行抛出异常，
这一定是它：
if(den==0) throw new ArithmeticException();
不要以0为分母来调用此函数。