刷题的狂欢-----JAVA每日三练-----第十三天_等我追上你，相约在西电。

努力刷题，每日三题，题目来源于《 Java大学实用教程（第四版）》
第一题
编写一个类，该类的创建对象可以计算等差数列的和。

package homework;

import java.util.Scanner;

public class Demo1 {

    static double work(double a,double d,int n){//  a:首项  d：公差  n：项数
        double sum;
        sum = a*n+((n*(n-1))*d)/2;
        return sum;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入首项：");
        double a = scanner.nextDouble();
        System.out.println("输入公差：");
        double d = scanner.nextDouble();
        System.out.println("输入项数：");
        int n = scanner.nextInt();
        Demo1 demo1 = new Demo1();
        double answer = demo1.work(a,d,n);
        System.out.println(answer);
    }
}

第二题
编写一个类，该类创建了一元二次方程共有的属性和功能，即该类有刻画方程系数的3个成员变量以及计算实根的方法。要求，该类的所有对象共享常数项。

package homework;

import java.util.Scanner;

public class Demo3 {
    static class Work{
        private double a;
        private double b;
        private double c;

        public double getA() {
            return a;
        }

        public double getB() {
            return b;
        }

        public double getC() {
            return c;
        }

        public void setA(double a) {
            this.a = a;
        }

        public void setB(double b) {
            this.b = b;
        }

        public void setC(double c) {
            this.c = c;
        }

        static void method(double a, double b, double c){
            double temp;
            temp = b*b-4*a*c;
            if(temp>=0) {
                double x1 = (-b + Math.sqrt(temp)) / 2 * a;
                double x2 = (-b - Math.sqrt(temp)) / 2 * a;
                System.out.println("x1=" + x1);
                System.out.println("x2=" + x2);
            }else{
                System.out.println("此方程无解！");
            }

        }
    }
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入a的值：");
        double a = scanner.nextDouble();
        System.out.println("输入b的值：");
        double b = scanner.nextDouble();
        System.out.println("输入c的值：");
        double c = scanner.nextDouble();
        Work work = new Work();
        work.method(a,b,c);
    }
}

第三题
编写两个类：A和B，A创建的对象可以计算两个正整数的最大公约数，B创建的对象可以计算两个数的最小公倍数。要求：B类中有一个成员成员变量是用A类声明对象。

package homework;

import java.util.Scanner;

public class Demo4 {
    static class A{
        public int hanshu(int x,int y){
            int c;
            c=x%y;
            while(c!=0){
                x=y;
                y=c;
                c=x%y;
            }
            return y;
        }
    }
    static class B {
        A a = new A();

        public int hanshu1(int x, int y) {
            int temp;
            temp = (x * y)/(a.hanshu(x, y));
            return temp;
        }
    }
        public static void main(String []args) {
            Scanner scanner = new Scanner(System.in);
            int x=scanner.nextInt();
            int y=scanner.nextInt();
            A a = new A();
            int d=a.hanshu(x,y);
            B b = new B();
            int e =b.hanshu1(x,y);
            System.out.println("最大公约数: "+d);
            System.out.println("最小公倍数: "+e);
            scanner.close();
        }
    }

打卡。