Question

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因此，对于comp sci中的赋值，我需要访问父类中的变量。我有类似

的东西

//import anything?


public class HW6Fraction extends Fraction{
  public HW6Fraction(int num, int denom){
    super();
  }

  public Fraction add(Fraction f) { //Add method
    int num = super().getNumerator + f.getNumerator();
    int denom = super().getDenominator + f.getDenominator();
    Fraction result = new Fraction(num, denom);
    return result;
  }

  public Fraction subtract(Fraction f) { //Subtract method
    int num = super().getNumerator - f.getNumerator();
    int denom = super().getDenominator - f.getDenominator();
    Fraction result = new Fraction(num, denom);
    return result;
  }
}

作为子类，类似于父类：

//Assignment 2 - problem 3, p. 125
/*
  Add, subtract, multiply, and divide methods to the Fraction class
  (section 3.8).  Also, add two more constructors.  One of the constructors
  will have no parameters; it initializes the fraction to 0/1.  The other
  constructor will have one parameter, representing the numerator of the
  fraction; the denominator of the fraction will be 1.  Write a TestFraction
  class (similar to the TestAccount class of Section 3.6) that creates two
  Fraction objects and tests the behavior of all constructors and instance
  methods in the Fraction class.

    Logic:
    Addition - ((numerator of fraction 1 * denominator of fraction 2) +
                (numerator of fraction 2 * denominator of fraction 1)) /
                (denominator of fraction 1 * denominator of fraction 2)

    Subtraction - ((numerator of fraction 1 * denominator of fraction 2) -
                  (numerator of fraction 2 * denominator of fraction 1)) /
                  (denominator of fraction 1 * denominator of fraction 2)

    Multiplication - (numerator of fraction 1 * numerator of fraction 2) /
                     (denominator of fraction 1 * denominator of fraction 2)

    Division - (numerator of fraction 1 * denominator of fraction 2) /
               (denominator of fraction 2 * numerator of fraction 1)
*/


public class Fraction {
  private int numerator; //Numerator of fraction
  private int denominator; //Denominator of fraction

  public Fraction(int num, int denom) { //Constructor
    numerator = num;
    denominator = denom;
  }

  public Fraction() { //Constructor w/ no parameters
    new Fraction(0, 1);
  }

  public Fraction(int num) { //Constructor w/ numerator parameter
    numerator = num;
    int denom = 1;
  }

  public int getNumerator() { //getNumerator method
    return numerator;
  }

  public int getDenominator() { //getDenominator method
    return denominator;
  }

  public void setNumerator(int num) { //setNumerator method
    numerator = num;
  }

  public void setDenominator(int denom) { //setDenominator method
    denominator = denom;
  }

  public Fraction add(Fraction f) { //Add method
    int num = numerator * f.getDenominator() + f.getNumerator() *
              denominator;
    int denom = denominator * f.getDenominator();
    Fraction result = new Fraction(num, denom);
    return result;
  }

  public Fraction subtract(Fraction f) { //Subtract method
    int num = numerator * f.getDenominator() - f.getNumerator() *
              denominator;
    int denom = denominator * f.getDenominator();
    Fraction result = new Fraction(num, denom);
    return result;
  }

  public Fraction multiply(Fraction f) { //Multiply method
    int num = numerator * f.getNumerator();
    int denom = denominator * f.getDenominator();
    Fraction result = new Fraction(num, denom);
    return result;
  }

  public Fraction divide(Fraction f) { //Divide method
    int num = numerator * f.getDenominator();
    int denom = denominator * f.getNumerator();
    Fraction result = new Fraction(num, denom);
    return result;
  }
}

这些行是我遇到问题的地方：

int num = super().getNumerator + f.getNumerator();

我想知道这是否有适当的术语？

Answer 1

您的HW6Fraction类从其父类继承该方法

所以你可以写：

int num = getNumerator() + f.getNumerator();

如果您的HW6Fraction还声明了getNumerator()方法，并且您想要调用父类中定义的getNumerator()：

int num = super.getNumerator() + f.getNumerator();

Answer 2

getNumerator是一个公共函数，因此任何引用您的类的东西都应该能够调用它，包括所有子类。

当您从类继承时，您继承了所有公共成员和受保护成员，因此它们都应该是您正在使用的子类的一部分。从技术上讲，只要调用getNumerator()就可以正常工作，你就不需要在前面添加任何特殊内容。

或者，this.getNumerator()将明确声明您希望与当前正在执行的对象关联的getNumerator函数。

使用super（）或对象在父类中访问变量？

2 个答案: