使用枚举实现switch中使用String作为条件

柔光的暖阳◎ 2022-06-13 03:41 405阅读 0赞

# 使用枚举实现switch中使用String作为条件 #

**以根据字符串类型的 + - \* /作为判断条件 , 实现简单计算器为例子。**

**枚举类：**

public enum OperationEnum {
        A("+"), B("-"), C("*"), D("/");     
        private String operate;             
        private OperationEnum(String operate) {
            this.operate = operate;
        }
        private String getOperate() {   
            return operate;
        }
        public static OperationEnum val(String operate) {
            for(OperationEnum s : values()) {    //values()方法返回enum实例的数组
                if(operate.equals(s.getOperate()))
                    return s;
            }
            return null;
        }
    }

**业务实现：**

public class Operation { 
        public static double getResult(double numberA, double numberB, String operation) {
            double result = 0d;
            OperationEnum operationEnum = OperationEnum.val(operation);
            switch (operationEnum) {
                case A:
                    result = numberA + numberB;
                    break;
                case B:
                    result = numberA - numberB;
                    break;
                case C:
                    result = numberA * numberB;
                    break;
                case D:
                    result = numberA / numberB;
                    break;
            }
            return result;
        }
    }

**可以用下面的主方法测试：**

public class Calculation { 
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
    
            try {
                System.out.println("请输入数字A:");
                String numberA = scanner.nextLine();
                System.out.println("请输入数字B:");
                String numberB = scanner.nextLine();
                System.out.println("请输入操作符:");
                String operate = scanner.nextLine();
                double result = getResult(Double.valueOf(numberA), Double.valueOf(numberB), operate);
                System.out.println(result);
            } catch (Exception e) {
                System.out.println("您的输入有误： " + e.getMessage());
            }
        }
    }