I am writing a java program that takes a number, x, as input from the user, sums all numbers from 1 to x (including x) that are divisible by 3, and displays the sum. it compiles without error but when I execute the program, it gets stuck in the loop and continues executing until I close the command prompt. I think the problem is inside the parenthesis after "for". I tried replacing the commands inside the loop with a simple
System.out.println("Hello");
and I got hundreds of Hello's streaming down the command prompt window. What am I doing wrong?
public static void main(String[] args){
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter a number");
int x = keyboard.nextInt();
int i, total = 0;
for (i = 0; i <= x; i=+3)
{
total =+ i;
}
System.out.println("The sum is " + total);
}
Your =+ should be +=.
total =+ i; is the same as total = +i; which is the same as total = i;.
Your assignment is wrong. At the time being, you are simply assigning the counter to 3.
i += 3
You've done the same with your total variable as well. You can fix it in the same way:
total += i;
Wrong operator it is endlees loop. Use += not =+
i += 3
just fix when you increase the i and the total. Here is the class to compile and run :
import java.util.Scanner;
class keyboard {
public static void main(String[] args){
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter a number");
int x = keyboard.nextInt();
int i, total = 0;
for (i = 0; i <= x; i+=3)
{
total += i;
}
System.out.println("The sum is " + total);
}
}
Related
I need to write a code where you insert 10 grades and get back the average of those ten grades. I know how to do it, except I don't know how to calculate the sum of all the grades. I found on this site this code:
public int sumAll(int... nums) { //var-args to let the caller pass an arbitrary number of int
int sum = 0; //start with 0
for(int n : nums) { //this won't execute if no argument is passed
sum += n; // this will repeat for all the arguments
}
return sum; //return the sum
}
so I wrote my code like this and it worked!:
import java.util.Scanner;
public class Loop7 {
public static void main(String[] args) {
Scanner scan = new Scanner (System.in);
System.out.println("Please enter how many grades you want to insert : ");
int num1 = scan.nextInt();
int num;
double sum =0;
for(int i= 0; i<num1; i++)
{
System.out.println("Please enter a grade: ");
num = scan.nextInt();
sum += num;
}
System.out.println("the average is: "+(sum)/num1);
}
so my question is what sum+=num; mean? how does that line give me the sum? and why I had to write double sum= 0?
Over here I explain each of those lines to better help you understand this code.
public class Loop7 {
public static void main(String[] args) {
Scanner scan = new Scanner (System.in); //this is what allows the user to input their data from the console screen
System.out.println("Please enter how many grades you want to insert : "); //this just outputs a message onto the console screen
int num1 = scan.nextInt(); //This is the total number of grades the user provides and is saved in the variable named num1
int num; //just a variable with nothing in it (null)
double sum =0; //this variable is to hold the total sum of all those grades
for(int i= 0; i<num1; i++) //loops as many times as num1 (if num1 is 3 then it loops 3 times)
{
System.out.println("Please enter a grade: "); //output message
num = scan.nextInt(); //every time the loop body executes it reads in a number and saves it in the variable num
sum += num; //num is then added onto sum (sum starts at 0 but when you add 3 sum is now 3 then next time when you add 1 sum is now 4 and so on)
}
System.out.println("the average is: "+(sum)/num1); //to get the average of a bunch of numbers you must add all of them together (which is what the loop is doing) and then you divide it by the number of items (which is what is being done here)
}
sum += num; Means that your sum which is declared 0 is added with num which you get from the console. So you simply make this: sum=sum+num; for the cycle. For example sum is 0, then you add 5 and it becomes sum=0+5, then you add 6 and it becomes sum = 5 + 6 and so on. And it is double because you are using division.
The reason you needed to write
double sum = 0.0;
is because you needed to initialize the sum first. Next the
sum += num;
means
sum = sum + num;
just in a more simple way.
Hey guys I need help with this assignment. When I run what I have it just loops forever, help would be much appreciated. Here's what my assignment is:
Write a program segment on the following page which reads a sequence of integers from the keyboard until 0 (zero) is entered. As it is entered print each integer (except for the 0 that stops the program) and at the average of the integers entered.
Each non-zero integer is printed on a separate line.
this continues until a zero is read, at which point the segment stops.
Here's what I have so far:
import java.util.Scanner;
public class List {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
int boom = 0;
int sum = 0;
double average = 0;
int count = 0;
System.out.println("Enter a nonzero integer, please!");
boom = keyboard.nextInt();
while (boom != 0) {
sum += boom;
count++;
average = ((double) sum) / count;
System.out.println("The average is " + average);
}
}
}
You read the keyboard input only once. That's what you should do:
while (boom=keyboard.nextInt() != 0) {
sum += boom;
count++;
average = ((double)sum) / count;
System.out.println ("The average is " + average);
}
It will loop forever if you enter a non-zero integer at the boom=keyboard.nextInt() stage. The reason why is that boom never changes in your while block and the condition for stopping is that boom does not equal zero.
You'll need to set boom to a non-zero value outside of the loop and move your assignment to boom of the int from the keyboard inside the loop.
I thought my code was correct but when I ran it, my output statements at the bottom wouldnt produce. I'm asking the keyboard to enter any number and then to end by entering -1. My while loop includes adding numbers, creating a sum, as well as giving the amount of even numbers. When I test my code I've been entering just 1,2,3,4 hoping to produce 4 total numbers. 2 even, and a sum of 10. Why isnt' my code getting to the print statements?
public static void main(String[] args) {
Scanner sc = new Scanner (System.in);
System.out.println("Please enter a number. Enter -1 to stop program.");
int num = sc.nextInt();
int counter = 0;
int even = 0;
int sum = 0;
while (num != -1)
{
counter += 1;
sum += num;
if (num%2 == 0)
{
even +=1;
}
}
System.out.println("You have entered "+ counter + "number(s)");
System.out.println("You have entered "+ even + "even numbers");
System.out.println("The sum for the numbers you entered is "+ sum);
}
You never get the input again so the loop runs infinitely. You need to get the value again.
while (num != -1)
{
...
num = sc.nextInt();
}
num gets set before you enter the loop.
So, when does the num change inside the while loop? It doesn't. That's why your code won't exit the loop.
I suggest moving the
num = sc.nextInt();
inside the loop.
I am writing a program that reads a sequence of positive integers input by the user. User will only enter one integer at a time.Then it will compute the average of those integers. The program will end when user enters 0. (0 is not counted in the average).The program will print out the average once the program ends.
Question: My code stops working when I gets to the while loop hence it doesn't compute the input by user, hence prints out nothing. Why doesn't my while loop compute the average from the user's inputs? Appreciate your guidance :)
import java.util.Scanner;
public class AverageOfIntegers {
public static void main(String[] args) {
int integer;
double sum;
sum = 0;
double average;
Scanner input = new Scanner(System.in);
int count; count = 0;
average = 0;
System.out.println("Please enter an integer: ");
integer = input.nextInt();
while (integer != 0) {
count = count + 1;
sum = sum + integer;
average = sum / count;
}
System.out.println("Average = " + average);
}
}
This is because you are never actually summing over more than one integer. The user only ever enters one number. As a result your loop is essentially acting on just the one number. You need to put the input inside the while loop and save a running sum and count there. Something more like this
while (integer != 0) {
count += 1;
sum += integer;
average = sum / count;
integer = input.nextInt();
}
Explanation
First of all, when you define data types, you can set their default value in the definition. Ex:
double sum = 0;
vs
double sum;
sum = 0;
Secondly, sum = sum + integer; is the same as: sum += integer;
Thirdly, count = count + 1; is the same as: count += 1 OR (and better yet), count++;
As for your actual algorithm, there is one problem and one suggestion:
you are not changing integer's value after each loop. So, you can
either do that in the while condition: while ((integer =
input.nextInt()) != 0) { or, at the end of each loop:
while (integer != 0) {
count ++;
sum += integer;
average = sum / count;
integer = input.nextInt();
}
This is a suggestion for technically better code (in my opinion), but it looks better, is more intuitive and requires less calculations to calculate the average after the while loop is done instead of during. That way, you only calculate it once, where needed, vs. every loop, which is not needed.
________________________________________________________________________________
The Code (complete class)
public class AverageOfIntegers {
public static void main(String[] args) {
int integer;
double sum = 0;
double average = 0;
Scanner input = new Scanner(System.in);
int count = 0;
System.out.println("Please enter an integer: ");
// set integer = to the nextInt() while looping so it calculates properly
while ((integer = input.nextInt()) != 0) {
count ++;
sum += integer;
}
average = sum / count; // calculate the average after the while-loop
System.out.println("Average = " + average);
}
}
________________________________________________________________________________
Example input/output:
Please enter an integer:
5
10
15
0
Average = 10.0
So it did 5 + 10 + 15 = 30 (which is the sum), and then the average is 30 / 3 (30 is the sum, 3 is the count), and that gave you Average = 10.0.
You need to move integer = input.nextInt(); inside the loop, so your program will collect inputs in a loop. See the corrected version:
import java.util.Scanner;
public class AverageOfIntegers {
public static void main(String[] args) {
int integer = 0, count = 0;
double sum = 0.0, average = 0.0;
Scanner input = new Scanner(System.in);
System.out.println("Please enter an integer: ");
integer = input.nextInt();
while (integer != 0) {
count = count + 1;
sum = sum + integer;
System.out.println("Please enter an integer: ");
integer = input.nextInt();
}
average = sum / count;
System.out.println("Average = " + average);
}
}
The problem is that the input.nextInt() should be part of the loop. The way you wrote it, the code gooes into an infinite loop whenever the first input is non-zero. Instead, do:
while ((integer = input.nextInt()) != 0) {
count = count + 1;
sum = sum + integer;
average = sum / count;
}
In the loop:
while (integer != 0) {
count = count + 1;
sum = sum + integer;
average = sum / count;
}
This will only stops when integer is 0, but this variable is not changing in the loop, so it will never be 0 if it wasn't already in the first place.
According to what you said you want to do, you should probably repeat the call to integer = input.nextInt(); inside your loop, lke this:
System.out.println("Please enter an integer: ");
integer = input.nextInt();
while (integer != 0) {
count = count + 1;
sum = sum + integer;
System.out.println("Please enter an integer: ");
integer = input.nextInt();
}
average = sum / count;
Also, as others have said, you only need to compute the average once after the loop, so I moved it too.
I'm writing a program for homework that is supposed to read in an unspecified number of 0-100 scores (maximum of 100 scores) and stop after -1 or any negative number is entered.
I've put this into a Do While loop that is set to terminate when -1 is pulled in through Scanner. The loop has a counter that keeps track of how many times the loop has been gone through, an adder that adds all the input lines together to later compute an average, and a means to send the input value to an array after it has checked to see if the number is -1.
Instead of doing this, the loop only increments the counter every 2 loops and -1 will only terminate the loop on an even cycle number, other wise it will wait until the next cycle to terminate. This completely baffles me, I have no idea why it's doing this. Could someone point out the error? Thanks in advance! This is all I have so far.
import java.util.Scanner;
public class main {
//Assignment 2, Problem 2
//Reads in an unspecified number of scores, stopping at -1. Calculates the average and
//prints out number of scores below the average.
public static void main(String[] args) {
//Declaration
int Counter = 0; //Counts how many scores are
int Total = 0; //Adds all the input together
int[] Scores = new int[100]; //Scores go here after being checked
int CurrentInput = 0; //Scanner goes here, checked for negative, then added to Scores
Scanner In = new Scanner(System.in);
do {
System.out.println("Please input test scores: ");
System.out.println("Counter = " + Counter);
CurrentInput = In.nextInt();
Scores[Counter] = CurrentInput;
Total += In.nextInt();
Counter++;
} while ( CurrentInput > 0);
for(int i = 0; i < Counter; i++) {
System.out.println(Scores[i]);
}
System.out.println("Total = " + Total);
In.close();
}
}
CurrentInput = In.nextInt();
Scores[Counter] = CurrentInput;
Total += In.nextInt();
You are calling twice In.nextInt(), i.e., you are reading two lines in each loop iteration.
CurrentInput = In.nextInt();
Scores[Counter] = CurrentInput;
Total += CurrentInput;
Use this instead.