20165203 四则运算（第二阶段）总结

一、需求分析

1.通过命令行输入生成题目的数量，随机生成题目。
2.生成的题目不重复。
3.生成的四则运算题目支持整数、支持多运算符。
4.生成的四则运算题目支持真分数。
5.能够根据作答情况统计正确的个数。能够根据作答情况统计正确的个数。
6.能够根据作答情况输出正确率。

二、设计思路

本周的新功能主要是在运算题目可以支持真分数上，所以设计也主要是围绕于此。增加一个类，这个类用来判断是否为真分数。若为真分数，则进入真分数的计算类。若不为真分数，则进入整数的计算类。此外就是我们增加了可以输出正确率的功能，这个就是增加一个变量，它的值为正确的题目个数除以总题目个数即可。

UML图

三、核心代码

1.各运算值的计算：


public class RationalNumber {
    private int numerator, denominator;

    public RationalNumber(int numer, int denom) {
        if (denom == 0)
            denom = 1;
        if (denom < 0) {
            numer = numer * -1;
            denom = denom * -1;
        }

        numerator = numer;
        denominator = denom;
        reduce();
    }

    public int getNumerator() {
        return numerator;
    }

    public int getDenominator() {
        return denominator;
    }

    public RationalNumber reciprocal() {
        return new RationalNumber(denominator, numerator);
    }

    public RationalNumber add(RationalNumber op2) {
        int commonDenominator = denominator * op2.getDenominator();
        int numerator1 = numerator * op2.getDenominator();
        int numerator2 = op2.getNumerator() * denominator;
        int sum = numerator1 + numerator2;

        return new RationalNumber(sum, commonDenominator);
    }

    public RationalNumber subtract(RationalNumber op2) {
        int commonDenominator = denominator * op2.getDenominator();
        int numerator1 = numerator * op2.getDenominator();
        int numerator2 = op2.getNumerator() * denominator;
        int difference = numerator1 - numerator2;

        return new RationalNumber(difference, commonDenominator);
    }

    public RationalNumber multiply(RationalNumber op2) {
        int numer = numerator * op2.getNumerator();
        int demon = denominator * op2.getDenominator();

        return new RationalNumber(numer, demon);
    }

    public RationalNumber divide(RationalNumber op2) {
        return multiply(op2.reciprocal());
    }

    public boolean isLike(RationalNumber op2) {
        return (numerator == op2.getNumerator() && denominator == op2.getDenominator());
    }

    public String toString() {
        String result;

        if (numerator == 0)
            result = "0";
        else if (denominator == 1)
            result = numerator + "";
        else
            result = numerator + "/" + denominator;
        return result;
    }

    private void reduce() {
        if (numerator != 0) {
            int common = gcd(Math.abs(numerator), denominator);

            numerator = numerator / common;
            denominator = denominator / common;
        }
    }

    private int gcd(int num1, int num2) {
        while (num1 != num2)
            if (num1 > num2)
                num1 = num1 - num2;
            else
                num2 = num2 - num1;
        return num1;
    }


    public int compareTo(RationalNumber answer1) {
        if (answer1.getDenominator() == this.getDenominator() && answer1.getNumerator() == this.getNumerator())
            return 1;
        if (answer1.getNumerator() != this.getNumerator() && answer1.getDenominator() != this.getDenominator())
            return 0;
        else
            return Integer.parseInt(null);
    }
}

2.计算正确率

num=scan.nextInt();
accuracy = (float)correct/num;
System.out.printf("正确率：%.2f",accuracy*100  );

3.利用本周学到的计时器知识，设计了一个计时器代码：


public static void timer1() {
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            public void run() {
                System.out.println("--请加快操作速度(Quickly)--");
            }
        }, 5000);// 毫秒
    }

代码链接