Cannot store multiple input value in Java

Question

I'm having a problem of storing multiple input value in Java. First, I'm using an ArrayList to store how many inputs the user has entered. Then I want to do the calculation after collect all the input.

My program allows user to enter 5 different values between 1 to 5. 1 is equal to 100, 2 is equal to 200, 3 is equal to 300, 4 is equal to 400, 5 is equal to 500

I create an Array to store these values

double numberArray[] = {100, 200, 300, 400, 500};

When user enters 1, the ArrayList will store the first input value. When user enters 2, the ArrayList will store the second input value and so on. When user hit "n", it will exit and do the addition. It means it will add 100 and 200 together which the output will equal to 300.

However, the problem is when the user keeps input the number, my program will only add up the total of the first input together which is 100 + 100 even I enter 2 as the second input.

Here is my code:

import java.util.*;

public class Total{

   static int total;
   public static void main(String[] args) {

    int numberArray[] = {100, 200, 300, 400, 500};

    List<String> list = new ArrayList<String>();
    Scanner input = new Scanner(System.in);

    do{
        System.out.println("Add item? Please enter \"y\" or \"n\"");
        if (input.next().startsWith("y")){
            System.out.println("Enter item number: ");
            list.add(input.next());
            if (list.contains("1")){
                int item1 = numberArray[0];
                total = total + item1;
            } else if(list.contains("2")){
                int item2 = numberArray[1];
                total = total + item2;
            } else if(list.contains("3")){
                int item3 = numberArray[2];
                    total = total + item3;
            } else if(list.contains("4")){
                    int item4 = numberArray[3];
                total = total + item4;
            } else {
            System.out.println("You have entered invalid item number!");
            break;
            }               
        }else{
            System.out.println("You have entered all the item(s).");
            break;
        }       
     } while(true);
             System.out.println(The total is: " + total);
     }
}

You should have error that cannot make a reference to non-static variable total from static main method. — Alex
– Alex, Commented Oct 9, 2012 at 5:24
class variable total should be static, otherwise your code will not complie — Jayy
– Jayy, Commented Oct 9, 2012 at 5:29
You have multiple issues in your code, but the most immediate ones are that you're reading from input twice, as MadProgrammer noted, and the way you detect which option was entered is fundamentally flawed. It's pretty simple to see where your error lies; just trace what's in the list at each step. After you put 1 in the list, it will always be in the list, even the second time around. How would the latter if statements ever be called in this case? — Mark Peters
– Mark Peters, Commented Oct 9, 2012 at 5:29

o_o · Accepted Answer · 2012-10-09 05:40:39Z

2

Consider what happens when I run the program.

First run through: I answer 'y'; and enter 1. list.contains("1") evaluates to true. All is well, and total=100.
Second run through: I answer 'y'; and enter 2. However, list.contains("1") still evaluates to true - whoops! 100 is added again, when clearly 200 should be added. In fact, 100 will be added for every next run through, since list.contains("1") will always be true from now on.

Instead of using a list to store the user input, use a String variable instead. Even better, consider using input.nextInt(), and look up the value in the table.

Also, you forgot the case for "5".

answered Oct 9, 2012 at 5:40

o_o

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1 Comment

maba Over a year ago

+1; This is what is causing the problem. The list will always contain the old choices.

Jayy · Accepted Answer · 2012-10-09 05:56:41Z

1

IF conditions should be modified to get the expected output like below

if (list.get(list.size() -1).contains("1"))

See full code with all errors fixed:

    import java.util.*; 

public class Total{ 

   static int total; 
   public static void main(String[] args) { 

    int numberArray[] = {100, 200, 300, 400, 500}; 

    List<String> list = new ArrayList<String>(); 
    Scanner input = new Scanner(System.in); 

    do{ 
        System.out.println("Add item? Please enter \"y\" or \"n\""); 
        if (input.next().startsWith("y")){ 
            System.out.println("Enter item number: "); 
            String temp = input.next(); //store the user inputed element
            list.add(temp); //add that element in list
            //System.out.println(input.next()); 

            //Now use the temporary variable in if conditions
            if (temp.contains("1")){ 
                int item1 = numberArray[0]; 
                total = total + item1; 
            } else if(temp.contains("2")){ 
                int item2 = numberArray[1]; 
                total = total + item2; 
            } else if(temp.contains("3")){ 
                int item3 = numberArray[2]; 
                    total = total + item3; 
            } else if(temp.contains("4")){ 
                    int item4 = numberArray[3]; 
                total = total + item4; 
            } else { 
            System.out.println("You have entered invalid item number!"); 
            break; 
            }                
        }else{ 
            System.out.println("You have entered all the item(s)."); 
            break; 
        }        
     } while(true);

        System.out.println("Total is: " + total);
    } 
}

edited Oct 9, 2012 at 5:56

answered Oct 9, 2012 at 5:37

Jayy

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7 Comments

R.Spark Over a year ago

This one works, could you explain to me why I have to use "get()" and "size()-1"???

MadProgrammer Over a year ago

Why not just store the value in a local variable, add it to the list and use the local variable as the condition for the if statements?

Jayy Over a year ago

You are in a loop and you are doing two things, i) adding the inputted element into arraylist and also based on that inputted element you want to sum up the totals. So inorder to do the second task, you need the inputted element and that is already saved by you as per task 1. So we are fetchinng the last element of the arraylist to get the inputted element by giving list.get(list.size() -1).

Jayy Over a year ago

@MadProgrammer Yes definitely, i did not say that the above code is an optimized one... It just works to get his expected output.

MadProgrammer Over a year ago

@KaipaMSarma Not picking on you solution (really I'm not), just encouraging you to help lift the OP's coding standards (and understanding) ;)

|

MadProgrammer · Accepted Answer · 2012-10-09 05:36:55Z

1

You're reading twice from scanner

list.add(input.next());
System.out.println(input.next());

But discarding the second input...

UPDATE

Okay, so here's my take on it

public class TestScanner03 {

    private static int total;

    public static void main(String[] args) {

        int numberArray[] = {100, 200, 300, 400, 500};

        List<String> list = new ArrayList<String>();
        Scanner input = new Scanner(System.in);

        // Better to use a stateful flag then simply "break" the loop
        boolean stay = true;
        do {
            System.out.println("Add item? Please enter \"y\" or \"n\"");
            String next = input.next();
            // Catch case issues
            if (next.equalsIgnoreCase("y")) {
                System.out.println("Enter item number: ");
                next = input.next();
                try {
                    // Make sure that the user actually entered a numeric value
                    int value = Integer.parseInt(next);
                    switch (value) {

                        // Make sure the value is within range
                        case 1:
                        case 2:
                        case 3:
                        case 4:
                        case 5:
                            // Make sure we don't already have the value
                            if (!list.contains(next)) {
                                // Extract the "addition" from the number array...
                                total += numberArray[value - 1];
                                list.add(next);
                                System.out.println("Your total is now " + total);
                            } else {
                                System.out.println(next + " is already used");
                            }
                            break;

                        default:
                            break;

                    }
                } catch (NumberFormatException numberFormatException) {
                    System.out.println(next + " is not a valid number");
                }

            } else {
                System.out.println("You have entered all the item(s).");
                stay = false;
            }
        } while (stay);
        System.out.println("Your total is " + total);
    }

}

edited Oct 9, 2012 at 5:36

answered Oct 9, 2012 at 5:26

MadProgrammer

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3 Comments

R.Spark Over a year ago

I removed that line because it was for my testing only.

o_o Over a year ago

The line you mentioned in the update is for seeing whether the user wants to continue.

MadProgrammer Over a year ago

@o_o Yeah, I caught that after I posted, updated with example

Pradeep Pati · Accepted Answer · 2012-10-09 05:29:45Z

Your total is never getting incremented, rather, it is just printing the element in nth position.

            if (list.contains("1")){ //You entered 2, this is false, total = 0
                int item1 = numberArray[0];
                total = total + item1; // this doesn't get executed
            } else if(list.contains("2")){ //true
                int item2 = numberArray[1];
                total = total + item2; // total = 200
            } else if(list.contains("3")){ //false
                int item3 = numberArray[2];
                    total = total + item3; // still total = 200, as this is not executed
            } else if(list.contains("4")){ // false
                    int item4 = numberArray[3];
                total = total + item4; // not executed, still total = 200
            }

Hence, a better solution will be to use switch statement, or convert the input to int.

int input = Integer.parseInt(list.get(0));
if(input < 5)
{
  for(int i = 0; i< input; i++)
  total += numberArray[i];
}

Kumar Vivek Mitra · Accepted Answer · 2012-10-09 05:32:49Z

Simply try it this way....

Assign the value to a String variable and try it again...

String getUserInput = new Scanner(System.in).next();

The Code:

do{
        System.out.println("Add item? Please enter \"y\" or \"n\"");

        String getUserInput = new Scanner(System.in).next();

        if (getUserInput.startsWith("y")){
            System.out.println("Enter item number: ");
            list.add(getUserInput);
            System.out.println(getUserInput);
            if (list.contains("1")){
                int item1 = numberArray[0];
                total = total + item1;
            } else if(list.contains("2")){
                int item2 = numberArray[1];
                total = total + item2;
            } else if(list.contains("3")){
                int item3 = numberArray[2];
                    total = total + item3;
            } else if(list.contains("4")){
                    int item4 = numberArray[3];
                total = total + item4;
            } else {
            System.out.println("You have entered invalid item number!");
            break;
            }               
        }else{
            System.out.println("You have entered all the item(s).");
            break;
        }       
     } while(true); 
     }

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