I know its wrong but I really need help.

Question about the task

Resolved

I remember a similar exercise one or two levels back but for the life of me I cant remember the exact way to print an ongoing addition of all numbers input into the console. Please if someone can either give me a solution I can reverse engineer and or talk me through the exercise that would be awesome.

Use the keyboard to enter numbers and calculate their sum until the user enters the word "sum".
Display the resulting sum on the screen.

Hint: to read from the keyboard until the string 'exit' is input, do this:

BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
while (true)
{
	String s = buffer.readLine();
	if (s.equals("exit"))
		break;
}

Requirements:

The program must read data from the keyboard.
The program should stop reading data from the keyboard after the user enters the word "sum" in lowercase letters and presses Enter.
The program should work correctly if the user enters one number and the word "sum".
The program should work correctly if the user enters two numbers and the word "sum".
The program should work correctly if the user enters more than two numbers and the word "sum".
The program should display text on the screen.

package com.codegym.task.task05.task0529; import java.io.BufferedReader; import java.io.InputStreamReader; /* Console-based piggy bank */ public class Solution { public static void main(String[] args) throws Exception { BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in)); int sum; while (true) { String s = bufferedReader.readLine(); sum = Integer.valueOf(s); if (s.equals("exit")) { break; } else if (s.equals("sum")) { break; } else { System.out.println(s); } } } }

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Chloe Dinh

Level 9 , United States

30 August 2020, 22:36

1) you don't need the statement if (s.equals("exit")). It is just an example they give you. 2) you should initialize variable sum before starting the while loop. 3) The sum basically is an adding all of the numbers you read from the input. So each time you reach a number (using the while loop), sum will add that number to the current sum and create a new sum. The new sum become current sum and if the while loop continue running the new number is read and adding to the current sum and create new sum...program continues doing the adding until it hit the word "sum". That is why the variable sum needs to be initialized an value to begin with adding numbers.(its initialization should be 0) 4) The program reading the input as String type, to be able to calculate (says adding in this case) value should be integer, double or long type. So please parse the value into integer or double before adding it to the sum. 5) the last thing you should notice is if you parse the value from String to Integer right away after the statement of reading value from input, you will get an error, since the input include the word "sum", and the program cannot parse the word "sum" into Integer value. So a statement of if the program reads the word "sum", the program will breaks should be state before the statement of parsing String to integer. hope it helps

Chris

Level 19 , Newark, United States

30 August 2020, 23:10

Thank you for breaking everything down as well. That was such a tricky exercise but now I understand everything that I need to do next time I come across the problem. Thank you!

Nouser

Level 36 , Germany

29 August 2020, 17:33

Just follow the hint to the point and replace exit with sum. After that add the rest of your code without else if or else. break is doing that for you. If the break condition (sum has been entered) is true, the loop will get aborted and the code after break won't be executed. So then it's time to do the parsing to int and (not done yet) to add the input values to a result variable.

Chris

Level 19 , Newark, United States

29 August 2020, 18:37

I understand what you mean by parsing everything. I just still dont get it.

Nouser

Level 36 , Germany

30 August 2020, 07:01

OK, lets go through this and start with the hint. I just replace exit with sum

BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
while (true)
{
	String s = buffer.readLine();
	if (s.equals("sum"))
		break;
}

Now we need another variable that holds the result. I make it a double cause the task makers wanted to trick you ;) They asked for a number and not an int.

BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
double result = 0;
while (true)
{
	String s = buffer.readLine();
	if (s.equals("sum"))
		break;
}

As said, now the code lets us enter numbers and if we enter sum it stops the input. The code, that adds the input to the result variable we write after the break command. result = result + 1 you can writer shorter with result += 1

BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
double result = 0;
while (true)
{
	String s = buffer.readLine();
	if (s.equals("sum"))
		break;
    result += Double.parseDouble(s);
}

I used Double.parseDouble cause of task makers asking for numbers and I didn't use valueOf as you did just cause I'm used to it and it returns a primitive and not a Double object.

Nouser

Level 36 , Germany

30 August 2020, 07:03

Finally we just need to output the result. Of course that's done after the loop cause we want to do that just once.

BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
double result = 0;
while (true)
{
	String s = buffer.readLine();
	if (s.equals("sum"))
		break;
    result += Double.parseDouble(s);
}
System.out.println(result);

Done, I hope there are no typos in it.

Chris

Level 19 , Newark, United States

30 August 2020, 23:09

This made everything so much clearer for me the way you took the time to go step by step thank you.