要求在控制台输入一个计算表达式 按回车出计算结果

public class Work01 {
    public static void main(String[] args) {
        Scanner scanner 
            = new Scanner(System.in);
        System.out.println("请输入一个计算表达式:");
        String line = scanner.nextLine();
        //操作符的位置
        int index = 0;
        if((index = line.indexOf("+"))>0){
            print(index,line,1);
        }else if((index = line.indexOf("-"))>0){
            print(index,line,2);
        }else if((index = line.indexOf("*"))>0){
            print(index,line,3);
        }else if((index = line.indexOf("/"))>0){
            print(index,line,4);
        }
    }
    /**
     * 
     * @param index
     * @param type 1加 2减 3乘 4除
     */
    public static void print(int index,String line,int type){
            int a= 
                Integer.parseInt(
                    line.substring(0,index)
                );
            int b 
                =
                Integer.parseInt(
                    line.substring(index+1)    
                );
            if(type==1){
                System.out.println(a+"+"+b+"="+(a+b));
            }else if(type==2){
                System.out.println(a+"-"+b+"="+(a-b));
            }else if(type==3){
                System.out.println(a+"*"+b+"="+(a*b));
            }else if(type==4){
                System.out.println(a+"/"+b+"="+(a/b));
            }

    }