新手上路，记录学习过程，便于总结，如有不对或和优化的地方，欢迎大家指出！
代码如下：
package method;import java.util.Scanner;public class Demo06 {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("请输入第一个数：");while (scanner.hasNextDouble()){double i = scanner.nextDouble();System.out.println("请输入运算符：");String a=scanner.next();System.out.println("请输入第二个数");double j = scanner.nextDouble();switch (a){case "+" : add(i,j);break;case "-" : minus(i,j);break;case "*" : multiply(i,j);break;case "/" : divide(i,j);break;default:System.out.println("请输入合法的数字或运算符！");break;}System.out.println("输入任意字符可退出或输入数字继续计算...");}scanner.close();}public static double add(double i,double j){System.out.println(i+" + "+j+" = "+(i+j));return i+j;}public static double multiply(double i,double j){System.out.println(i+" * "+j+" = "+(i*j));return i*j;}public static double minus(double i,double j){System.out.println(i+" - "+j+" = "+(i-j));return i-j;}public static double divide(double i,double j){if (j==0){System.out.println("分母不能为零！");}else {System.out.println(i+" / "+j+" = "+(i/j));}return i/j;}}
程序运行的效果如下：
