error: int cannot be dereferenced java (repeat)

Question

I'm writing a simple Java program to do a temperature conversion, and I keep getting an error on line 8 (which I have marked in the code below) that the int cannot be dereferenced. I'm not sure exactly what this means, or how to fix it, and other questions here with the same error did not help with finding a solution for my error. The problem is: having the format:

 ?<int><int><int><int>

I have to solve the ? in the case, but taking into account the second vector is multiplied by 3, the third by 1 and the fourth by 0 and the last vector is subtracted.

class LeaderBoard{
  public static void main(String[] args){
    String errorFormat = "Format error: You must write 4 integers and one symbol ?";

    int[] list = null;
    int position = -1, j = 0;

    if(args.length!=5){
        System.err.println(errorFormat);
    }else{
        try {
            list = new int[4];
            for(int i=0;i<args.length;i++){
                if(position== -1 && args[i].equals("?")){
                    position = i;
                }else if((position!= -1 && args[i].equals("?")) || (j==4)){
                    //Hay mas de un ? o no hay ?
                    System.err.println(errorFormat);
                    System.exit(1);
                }else{
                    list[j] = Integer.parseInt(args[i]);
                    j++;
                }
            }
        } catch (NumberFormatException e) {
            System.err.println(errorFormat);
            System.exit(1);
        }

        System.out.println("The missing value is "+calculate(position,list)); 
    } 
}

static int calculate(int position, int[] list){
    position=0;
    for (int i=0; i<list.length; i++){
        if(list[1]==0){

position=list[1]*3+list[2]*1+list[3]*0+list[4]*(-1);
        }
    }   
    return 0;   
}}

When I execute the program I always get the value 0 as a result, altought i change the input values.

Could someone help me?

see [this answer](https://stackoverflow.com/questions/19109131/int-cannot-be-dereferenced-in-java) — Umer Farooq, Oct 03 '18 at 17:51

GBlodgett · Answer 1 · 2018-10-03T17:40:50.130

2

list[1] is a primitive type. You cannot call methods on it. So when you try to call equal (Did you mean equals()?) you get an error.

Beyond that your logic doesn't make sense. You're trying to compare an int to a String and then compare the boolean result to another int

edited Oct 03 '18 at 17:40

answered Oct 03 '18 at 17:32

GBlodgett

12,612
4
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Got it! But then, how can i obtain the position of the "?"symbol within the array? – gfdadaf Oct 03 '18 at 17:47
@gfdadaf Your array is an `int` array so it will not contain a `String`. – GBlodgett Oct 03 '18 at 17:51

score 0 · Accepted Answer · answered Oct 03 '18 at 17:57

0

In your calculate function you are passing position but your are not even making use of it and assigning 0 to it.

Also the for loop will throw an exception when i=1 as your code will try to access list[i+4]=list[5] which doesn't exist so will get ArrayIndexOutOfBound Exception.

Since your array contains only int types you don't need to worry about position of ? as ? is not of int type and you can probably use the below code:

static int calculate(int[] list){
    int position=0;           
    int calculatedValue = list[position]*3+list[position+1]*1+list[position+2]*0+list[position+3]*(-1);          

    return calculatedValue ;   
}

answered Oct 03 '18 at 17:57

Yug Singh

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Now the error disappeared but the final value is always 0 even using your code. – gfdadaf Oct 03 '18 at 18:10
Please check with different input. Maybe you are getting 0 for the passed input. For example if I input `?,1,2,3,4` the list array will be `[1,2,3,4]` and `calculate` function will return `1*3+2*1+3*0+4(-1)=1` – Yug Singh Oct 03 '18 at 18:13
True! Know i see. And if i'd like to use an if to detect the exact position of the ?, what should i do? – gfdadaf Oct 03 '18 at 18:21
@gfdadaf you dont have `?` in your int array. Why do you exactly want the position of `?` – Yug Singh Oct 03 '18 at 18:29
Because in the case someone write 1, 2 ? 3, 4 instead, the program must say this is not the correct position of the ?. I know i should write this info in the main question. – gfdadaf Oct 03 '18 at 18:31
@gfdadaf is the position of `?` fixed in the input that is in the beginning? I mean the input should always be `? n1,n2,n3,n4`? – Yug Singh Oct 03 '18 at 18:41
No, its position can change – gfdadaf Oct 03 '18 at 18:48
@gfdadaf but you will throw an error in that case as you mentioned in one of the previous comments - in the case someone write 1, 2 ? 3, 4 instead, the program must say this is not the correct position of the ? – Yug Singh Oct 03 '18 at 18:50
So should `?` always be at the first position in the args input? – Yug Singh Oct 03 '18 at 18:51
No, it can be in different positions like 1 2 3 4 ? – gfdadaf Oct 03 '18 at 18:57
@gfdadaf if that is the case then your logic should suffice. In you `main method` you are checking for `?` and if found you are making `position=i`. Now if you again get `?` then you are printing an error and doing `System.exit();` Otherwise you are adding the `int to list array of int type`. Finally you are calling `calculate` with the list array. – Yug Singh Oct 03 '18 at 19:01

error: int cannot be dereferenced java (repeat)

2 Answers2