Java学习之简单的计算器

运用String类的相关方法写的简单的计算器

public static void main(String[] args) {
    
     
	Scanner scanner = new Scanner(System.in);
    String str = scanner.next();
    int i = str.indexOf('+');
    scanner.close();
    if(i != -1)
    {
    
    
        System.out.println(new calcu().check("+",str,i));
        return;
    }
    i = str.indexOf('-');
    if (i != -1) {
    
    

        System.out.println(new calcu().check("-",str,i));
        return;
    }
    i = str.indexOf('*');
    if (i != -1) {
    
    

        System.out.println(new calcu().check("*",str,i));
        return;
    }
    i = str.indexOf('/');
    if (i != -1) {
    
    
        System.out.println(new calcu().check("/",str,i));
        return;
    }

}

    public int  left(String a,int i) {
    
    
        int l = Integer.parseInt(a.substring(0,i));
        return l;
    }
    public int  right(String a,int i) {
    
    
        int r = Integer.parseInt(a.substring(i+1));
        return r;
    }

    public String check(String code,String str,int i) {
    
    
            int sum=0;
            int l,r;
            l = left(str, i);
            r = right(str, i);
            switch (code) {
    
    
            case "+":
                sum = l + r;
                break;
            case "-":
                sum = l - r;
                break;
            case "*":
                sum = l * r;
                break;
            case "/":
                if(r != 0 ){
    
    
                        sum = l / r;
                    }
                else {
    
    
                    return "错误！被除数不能为0";
                }
                break;
            }
            return str + " = " + sum;
    }

希望可以和大家互相学习，谢谢大家！！！