public class juxing {        juxing(){        chang=1;        kuan=1;    }        double chang;        double kuan;        double mianji(){                return (chang*kuan);    }        public static void mian(String []ages){                juxing a=new juxing();                a.chang=3.2;                a.kuan=2.4;                System.out.println("呵呵哒"+a.mianji());            }}

public static void main(String[] args) {        // TODO 自动生成的方法存根        juxing a=new juxing();        System.out.println(a.mianji());                a.chang=3.2;                a.kuan=2;                System.out.println(a.mianji());    }

public class 运算 {    double 数字一;        double 数字二;        double a2;        void 运算方式 (String a){        switch(a){        case "加":            a2=数字一+数字二;            System.out.println(a2);        break;        case "+":            a2=数字一+数字二;            System.out.println(a2);        break;        case "-":            a2=数字一-数字二;            System.out.println(a2);        break;        case "减":            a2=数字一-数字二;            System.out.println(a2);        break;        case "*":            a2=数字一-数字二;            System.out.println(a2);        break;        case "乘":            a2=数字一*数字二;            System.out.println(a2);        break;        case "/":            a2=数字一-数字二;            System.out.println(a2);        break;        case "除":            a2=数字一/数字二;            System.out.println(a2);        break;        case "%":            a2=数字一%数字二;            System.out.println(a2);        break;        case "摩":            a2=数字一-数字二;            System.out.println(a2);        break;        default :            System.out.println("别逗好么，我问你你怎么算");        }    }

public static void main(String[] args) {        // TODO 自动生成的方法存根        运算 a=new 运算();        a.数字一=10.2;        a.数字二=3.3;        a.运算方式("/");