对于这个项目，我必须创建一个有理数类，它由两部分组成，一部分是int分子，另一部分是整型分母。我必须加上两个收缩，其中负分母必须移动到分子上。我还添加了getter和setter以及一个toString（）。数据应打印为分子/分母。我还必须为加法、减法、乘法和除法的成员方法编写代码，然后求反（？）我不确定最后一部分的意思。
我已经完成了这个类，但Eclipse在我键入"temp"的部分的加减法中给了我一个错误。如果我有什么不正确的地方，或者我遗漏了什么，请告诉我。
public class Rational {
private int numerator;
private int denominator;
public Rational()
{
numerator = 0;
denominator = 1;
}
public Rational(int n, int d, int num, int denom)
{
if (d < 0)
{
num = -n;
denom = d;
}
else if (d == 0)
{
num = n;
denom = 1;
}
else
{
num = n;
denom = 0;
}
}
public int getNumerator()
{
return numerator;
}
public int getDenominator()
{
return denominator;
}
public void setNumerator(int n)
{
numerator = n;
}
public void setDenominator(int n, int d, int num, int denom)
{
denominator = d;
if (d < 0)
{
num = -n;
denom = d;
}
else if (d == 0)
{
num = n;
denom = 1;
}
else
{
num = n;
denom = 0;
}
}
public String toString()
{
return numerator + "/" + denominator;
}
public boolean equals (Rational other)
{
if(numerator * other.denominator == denominator * other.numerator)
return true;
else
return false;
}
public boolean notequals(Rational other)
{
if (numerator * other.denominator != denominator * other.numerator)
return true;
else
return false;
}
//subtract method
public Rational subtract(Rational other)
{
Rational temp;
temp.numerator = numerator * other.denominator - denominator * other.numerator;
temp.denominator = denominator * other.denominator;
return temp;
}
//add method
public Rational add(Rational other)
{
Rational temp;
temp.numerator = numerator * other.denominator + denominator * other.numerator;
temp.denominator = denominator * other.denominator;
return temp;
}
public boolean lessThan(Rational other)
{
return(numerator * other.denominator < denominator * other.numerator);
}
public boolean greterThan(Rational other)
{
return(numerator * other.denominator > denominator * other.numerator);
}
public boolean lessThanEqualTo(Rational other)
{
return(numerator * other.denominator <= denominator * other.numerator);
}
public boolean greaterThanEqual(Rational other)
{
return(numerator * other.denominator >= denominator * other.numerator);
}
}
然而，我正在努力测试每一种方法。以下是我目前所拥有的：
public class Project4 {
public static void main(String[] args) {
Rational a = new Rational();
Rational b = new Rational();
Rational c;
c = a.add(b);
}
}
//Here goes commented code:
public class Rational
{
private int numerator; // You can declare private variables here all right
private int denominator;
// This constructor creates a new object of the class Rational. Objects are instances of that class, all right?
public Rational()
{
numerator = 0;
denominator = 1;
//private int numerator = 0;
//private int denominator = 1; // I get it, you need them even when not giving arguments, but it is better to do stuff in constructors. You better try to make declarations in the constructor and not in the begining of a class, if possible.
}
// Here is the constructor overriden, so you can create an instance that contains 4 arguments. (n,d,num,denom) Good.
public Rational(int n, int d, int num, int denom)
{
// You repeat yourself in the constructor.
// public void setDenominator(int n, int d, int num, int denom) does the same thing right?
// I don't remember now, but I think that on instantiation you can't use methods, if you don't add the word static.
// public static void setDenominator(int n, int d, int num, int denom) will make you able to call it in the constructor!
if (d < 0)
{
num = -n;
denom = d;
}
else if (d == 0)
{
num = n;
denom = 1;
}
else
{
num = n;
denom = 0;
}
}
public int getNumerator()
{
return numerator;
}
public int getDenominator()
{
return denominator;
}
public void setNumerator(int n)
{
numerator = n;
}
public void setDenominator(int n, int d, int num, int denom) // FIX IT. ADD STATIC
{
denominator = d;
if (d < 0)
{
num = -n;
denom = d;
}
else if (d == 0)
{
num = n;
denom = 1;
}
else
{
num = n;
denom = 0;
}
}
public String toString()
{
return numerator + "/" + denominator;
}
public boolean equals (Rational other)
{
if(numerator * other.denominator == denominator * other.numerator)
return true;
else
return false;
}
public boolean notequals(Rational other)
{
if (numerator * other.denominator != denominator * other.numerator)
return true;
else
return false;
}
//subtract method
public Rational subtract(Rational other)
{
Rational temp;
temp.numerator = numerator * other.denominator - denominator * other.numerator;
temp.denominator = denominator * other.denominator;
return temp;
} // THIS RETURNS temp THAT IS AN OBJECT OF THE TYPE Rational!!! Remember that.
//add method
public Rational add(Rational other)
{
Rational temp;
temp.numerator = numerator * other.denominator + denominator * other.numerator;
temp.denominator = denominator * other.denominator;
return temp;
}// THIS RETURNS temp THAT IS AN OBJECT OF THE TYPE Rational!!! Remember that.
public boolean lessThan(Rational other)
{
return(numerator * other.denominator < denominator * other.numerator);
}// What type is this method return? Here is the gap you must fill. If you learn how to handel what methods return, you will be fine. Try stuff out.
public boolean greterThan(Rational other)
{
return(numerator * other.denominator > denominator * other.numerator);
}
public boolean lessThanEqualTo(Rational other)
{
return(numerator * other.denominator <= denominator * other.numerator);
}
public boolean greaterThanEqual(Rational other)
{
return(numerator * other.denominator >= denominator * other.numerator);
}
}