Question

What would be the output if 1, 2, 3, and -1 were entered and please walk me through the process.

import java.util.Scanner;

public class Practice1

{

public static void main(String[] args)

{

int count = 0;

int sum = 0;

Scanner keyboard = new Scanner(System.in);

System.out.println("Enter integers or -1 to quit");

int anInt = keyboard.nextInt();

while(anInt != -1)

{

anInt = keyboard.nextInt();

sum += anInt;

count++;

}

anInt = keyboard.nextInt();

sum += anInt;

count++;

}

}

Answer 1

when you enter 1,2, 3 -1 what happens is first anInt outside while loop becomes 1.

Then anInt is not equal to 1 , execution starts inside while loop

first iteration:

Inside while loop , anInt is again read from keyoboard , now and integer value of 2 is read from keyboard

sum=sum+anInt which is sum=0+2=2

Count is incremented , it becomes 1 , then while loop checks in anItnt value is not equal to -1 , it's not equal hence while loop evaluates to true and hence again execution starts inside while loop .

second iteration:

Here again anInt is read from keyboard , when takes the value of 3 from keyboard

sum+=anInt, here sum has stored 2 from previous execution. hence sum becomes 2+3 = 5

Now again while loop checks if anInt value is -1 , hence this also evaluates to true as anInt value is now 3

Third iteration:

So execution once again start inside the loop

anInt value will be read from keyboard which reads -1 from the keyboard and now sum=sum+abInt = 5-1=4

sum values evaluates to 4.

Now while loop check if anInt value is -1 , this time it's true , hence execution comes out of while loop .

After while loop , again anInt is read from keyboard , so it waits for user input , so final sum value is dependent on the anInt value you enter + previous sum value (we got 4 from previous execution from while loop).

Output will be addition of 4 and the user input .

======================================

if  you want to sum up all the integers till user enters -1 ..above program is not perfect , I am giving you code if you want to sum up all the integers till you hit -1.

import java.util.Scanner;

class Main {

public static void main(String[] args) {

//System.out.println("Hello world!");

int count = 0;

int sum = 0;

Scanner keyboard = new Scanner(System.in);

System.out.println("Enter integers or -1 to quit");

int anInt;

do

{

anInt = keyboard.nextInt();

if(anInt == -1)

break;

sum+=anInt;

++count;

}while(true);

System.out.println("Number of reads : "+count+" , sum of integers: "+sum);

}

}

======================

//if you want output of sum of the integers entered until -1 , then use my above program. output is given below

Enter integers or -1 to quit
1 2 3 -1
Number of reads : 3 , sum of integers: 6

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//pls give positive rating , if my solution helped you,thanks!