简单四则运算

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("请输入四则运算表达式");
    String e=input.nextLine();
    double rs=jisuan(e);
    System.out.println(rs);
}

private static double jisuan(String e) {
    //1+2*3-6/2
    return jia(e);
}

private static double jia(String e) {
    String [] ee=e.split("\\+");
    double sum=0;
    for ( int i=0;ilength;i++ ){
        sum+=jian(ee[i]);}
    return sum;
}

private static double jian(String e) {//1+2*3-6/2

    String [] ee=e.split("\\-");
   double cha=cheng(ee[0]);
    for ( int i=1;ilength;i++ ){
        cha-=cheng(ee[i]);
    }
    return cha;
}

private static double cheng(String e) {
    String [] ee=e.split("\\*");
    double ji=chu(ee[0]);
    for ( int i=1;ilength;i++ ){
        ji*=chu(ee[i]);}
    return ji;
}

private static double chu(String e) {
    String [] ee=e.split("\\/");
    double shang=Double.parseDouble(ee[0]);
    for ( int i=1;ilength;i++ ){
        shang/=Double.parseDouble(ee[i]);
    }
    return shang;
}