[FIXED] How to add totals of array list object data after populating the array using a separate method

Issue

initialized the second array dimension but still getting a null pointer exception.

    final int LIQUORINV = 8;
    final int EACHCOUNT = 10;
    Liquor[][] invLiquor = new Liquor[LIQUORINV][EACHCOUNT];
    for( int i=0; i <= invLiquor.length; i++){
        System.out.println("\nWhich liquor are we counting?");
        String type = keyboard.next();
        for( int j=0; j < invLiquor[i].length; j++){
            invLiquor[i][j].setLiquorType(type);
            invLiquor[i][j] = new Liquor();
            System.out.println("What is the product name?: ");
            invLiquor[i][j].setLiquorName(keyboard.next());
            System.out.println("What is the count?: ");
            invLiquor[i][j].setLiquorCount(keyboard.nextDouble());
            System.out.println("What is the cost?: ");
            invLiquor[i][j].setLiquorCost(keyboard.nextDouble());
        }
    }

I think I did fix this next part however. so that's solved at least.

public static double GetLiquorCostTotal(Liquor[][] inv){
    double totalCost = 0;
    for( int i=0; i < inv.length; i++){
        double sum = 0;
        for( int j=0; j < inv[i].length; j++){
            sum += (inv[i][j].getLiquorCost() * inv[i][j].getLiquorCount());
        }
        System.out.println("\nThe total cost of the " + inv[i][0].getLiquorType() + 
            " inventory is: $" + sum);
        totalCost+=sum;
    }
    return totalCost;
}

Solution

The main issue here is your invLiquor array. My guess is you want to use invLiquor to store all the invs. In it's current form invLiquor does not have any association with invs. You might want to use a 2D array of Liquor, where the row will be the liquor categories. Here is a pseudo code that might be helpful.

// m = category count; n = item in each category;

Liquor[][] invLiquor = new Liquor[m][n]; 
 
for(int i=0;i<invLiquor.length();i++){
    System.out.println("\nWhich liquor are we counting?");
    String type = keyboard.next();
    
    for(int j=0;j<invLiquor[i].length();j++){
         invLiquor[i][j].setLiquorType(type);
         invLiquor[i][j] = new Liquor();
         System.out.println("What is the product name?: ");
         invLiquor[i][j].setLiquorName(keyboard.next());
         System.out.println("What is the count?: ");
         invLiquor[i][j].setLiquorCount(keyboard.nextDouble());
         System.out.println("What is the cost?: ");
         invLiquor[i][j].setLiquorCost(keyboard.nextDouble());
    }

}
double thisLiquorTotal = GetCostTotal(invLiquor);
System.out.println("\nThe total cost of the liquor inventory is: $" + thisLiquorTotal);

// the GetCostTotal method
double GetCostTotal(Liquor[][] invLiquor){
    double totalCost = 0;
    for(int i=0;i<invLiquor.length();i++){
       double sum = 0;
       for(int j=0;j<invLiquor[i].length();j++){
          sum+=invLiquor[i][j];
       }
       System.out.println("\nThe total cost of the " + invLiquor[i][0].getLiquorType() + 
            " inventory is: $" + sum);
       totalCost+=sum;

    }
   return totalCost;
}

This is a simple demo with a fixed number of Liquor in each category. If you want to have a different number of Liquor in different categories you might use an Array of Collections like LinkedListor ArrayList.

Answered By - Tanbir Ahmed