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How do you use a method to calculate 1 array parameter of grades and returns the total of the array?

My schoolwork is asking me to write a Java program. I'm not getting something quite right.
Basically I have to create a Java method that gets a user to enter x amount of grades (users choice), store the grades in an array and then add the grades in the array up to be called in the main method.
Here's my code:
import java.util.Scanner;
public class Sample {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Hello Drews, how many total grades do you want to process?");
int numberOfGrades = keyboard.nextInt();
int [] storeGrades = new int[numberOfGrades];
}
public static int getTotalScore(int numberOfGrades[]) {
Scanner keyboard = new Scanner(System.in);
int getTotalScore;
int []storeGrades;
for (int i = 0; i < getTotalScore; i++) {
System.out.println("Please enter grade " + (i + 1) + ": ");
int userGradeNumbers = keyboard.nextInt();
storeGrades[i] = userGradeNumbers;
sum += userGradeNumbers;
}
}
}
I'm getting an error at "sum" that it hasn't been resolved to a variable? It won't let me initialize sum within the for loop, nor the getTotalScore method. Why not?

First, get the grades. Then call the method to get the sum. Declare the sum and initialize it to 0 before your loop. Return it after. Like,
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Hello Drews, how many total grades do you want to process?");
int numberOfGrades = keyboard.nextInt();
int[] storeGrades = new int[numberOfGrades];
for (int i = 0; i < numberOfGrades; i++) {
System.out.println("Please enter grade " + (i + 1) + ": ");
storeGrades[i] = keyboard.nextInt();
}
System.out.println(getTotalScore(storeGrades));
}
public static int getTotalScore(int[] storeGrades) {
int sum = 0;
for (int i = 0; i < storeGrades.length; i++) {
sum += storeGrades[i];
}
return sum;
}

Your code has the right intent about it, but some of the ordering of things is a little off and there are syntactical issues at the moment.
I would advocate splitting up your code into two methods (unless you're specifically prohibited from doing so based on the assignment). One method to get the grades from the user, and another to sum the grades. The reason for this, is that you end up trying to both store and sum the grades at the same time (which is technically more efficient), but that doesn't teach you how to calculate a running total by iterating over an array (which is likely the point of the lesson).
One other thing that I would call out (which may be beyond where you are in the course right now), is that when you're using a Scanner, you need to validate that the user has typed what you think they've typed. It's entirely plausible that you want the user to type a number, and they type "Avocado." Because Java is strongly typed, this will cause your program to throw an exception and crash. I've added in some basic input validations as an example of how you can do this; the general idea is:
1) Check that the Scanner has an int
2) If it doesn't have an int, ask the user to try again
3) Else, it has an int and you're good to proceed. Store the value.
One last thing about Scanners. Remember to close them! If you don't, you can end up with a memory leak as the Scanner continues to run.
Below is how I would have revised your code to do what you want. Shoot me a comment if something doesn't make sense, and I'll explain further. I left comments inline, as I figured that was easier to digest!
package executor;
import java.util.Scanner;
public class StudentGrades {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
// Initial prompt to the user
System.out.println("Hello Drews, how many total grades do you want to process?");
// This loop validates that the user has actually entered an integer, and prevents
// an InputMismatchException from being thrown and blowing up the program.
int numberOfGrades = 0;
while (!keyboard.hasNextInt()) {
System.out.println("Sorry, please enter a valid number!");
keyboard.next();
}
// If the program makes it through the while loop, we know that the Scanner has an int, and can assign it.
numberOfGrades = keyboard.nextInt();
// Creating the array using the method getGrades().
int[] storedGrades = getGrades(numberOfGrades, keyboard);
// Calculating the total score using the method getTotalScore().
int totalScore = getTotalScore(storedGrades);
System.out.println("Total Score is: " + totalScore);
keyboard.close();
}
/**
* Asks the user to provide a number of grades they wish to sum.
* #param numberOfGrades the total number of grades that will be requested from the user.
* #param keyboard the scanner that the user will use to provide the grades.
* #return the summed grades as an int.
*/
public static int[] getGrades(int numberOfGrades, Scanner keyboard) {
int[] grades = new int[numberOfGrades];
// Asking the user i number of times, to enter a grade to store.
for (int i = 0; i < numberOfGrades; i++) {
System.out.println("Please enter grade " + (i + 1) + ":");
// More input validation to ensure the user can't store "Cat."
while (!keyboard.hasNextInt()) {
System.out.println("Sorry, please enter a valid number!");
keyboard.next();
}
int userEnteredGrade = keyboard.nextInt();
// Storing the user's entry.
grades[i] = userEnteredGrade;
}
return grades;
}
/**
* Sums all of the grades stored within an integer array.
* #param storedGrades the grades to be summed.
* #return the total value of summed grades.
*/
public static int getTotalScore(int[] storedGrades) {
int totalScore = 0;
for (int i = 0; i < storedGrades.length; i++) {
totalScore += storedGrades[i];
}
return totalScore;
}
}

Can I do a for loop after two consecutive if statements? [duplicate]

This question already has answers here:
What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?
(26 answers)
Closed 4 years ago.
I am working on a program that has to check for certain conditions (and give out an error message if they are not executed) before executing two for loops (one for the sum of grades entered and one for highest and lowest grades)and I'm not sure how to sequence them.
Also my code is getting me this error -->Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 and I'm not sure what to do to fix the error
If anyone can help me with the skeletons of the correct sequence I would truly appreciate it!
Here is my code (I know it looks crazy, sorry I'm learning!):
import java.util.Scanner;
public class Homework {
public static void main (String[] args) {
Scanner input = new Scanner(System.in);
int numberOfMarks, average, sum, total, mark;
numberOfMarks = 0;
int [] marks = new int[numberOfMarks];
int smallest, largest;
//System.out.println("Enter number of marks: ");
numberOfMarks = input.nextInt();
if(numberOfMarks<0) {
System.out.println("Number of marks must be greater than 0!!");
}
//System.out.println("Enter "+numberOfMarks+"marks: ");
mark = input.nextInt();
if(mark<0) {
System.out.println("Negative marks not allowed!!!");
} else if(mark>100) {
System.out.println("Marks above 100% not allowed!!!");
}
sum = 0;
for(int i = 0; i < marks.length; i++) {
sum += marks[i];
}
smallest=marks[0];
largest=marks[0];
for(int i=1;i<marks.length;i++) {
if(marks[i]>largest) {
largest=marks[i];
} else if(marks[i]<smallest) {
smallest=marks[i];
}
average = sum/numberOfMarks;
System.out.println("Highest Mark = "+largest);
System.out.println("Lowest Mark = "+smallest);
System.out.println("Average = "+average);
}
}
}

You can try this:
import java.util.Arrays;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
int numberOfSubjects, sum;
numberOfSubjects = 0;
System.out.print("Enter the total number of subjects: ");
numberOfSubjects = in.nextInt();
if(numberOfSubjects < 0){
System.out.println("Number of marks must be greater than 0!!");
}
else {
int []marks = new int[numberOfSubjects];
sum = 0;
System.out.print("Enter the marks: ");
// add condition inside for loop for marks not less than 1 or greater than 100
for(int i=0; i<marks.length; i++) {
marks[i] = in.nextInt();
}
// calculate total
for(int i = 0; i < marks.length; i++){
sum += marks[i];
}
// sort marks
Arrays.sort(marks);
System.out.println("Total: " + sum);
System.out.println("Average: " + sum/numberOfSubjects);
System.out.println("Minimum: " + marks[0]);
System.out.println("Maximum: " + marks[marks.length-1]);
}
}
}
Code flow should look like this. Even you can add condition of marks(not less than 1 or greater than 100) while reading marks.

Problem is in the logic, see comments bellow
import java.util.Scanner;
public class Homework {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int numberOfMarks, average, sum, total, mark;
numberOfMarks = 0;
/*there you are creating empty array
you told marks should have length of value numberOfMarks, but
numberOfMarks is equal to zero at this time
*/
int[] marks = new int[numberOfMarks];
int smallest, largest;
//System.out.println("Enter number of marks: ");
numberOfMarks = input.nextInt();
/*
not interesting conditions checking...
*/
for (int i = 0; i < marks.length; i++) {
/*
There you are trying to access 1st element of marks
- indexing from zero, as usual
But there is no first element, array has zero length, zero elements
Ok, you told array should have length of numberOfMarks, but it was
when value was zero, so if you will change numberOfMarks later, it
has no impact on the length of array
*/
sum += marks[i];
}
/*
stats computing, not important
*/
}
}
So, once you got user input for number of marks, then you can "recreate" - realloc / redefine the array, as before
marks = new int[numberOfMarks];
In your case bellow
//System.out.println("Enter number of marks: ");
numberOfMarks = input.nextInt();
Using variable in length of array does not means it will be bounded, so if variable in array length (in this case numberOfMarks) will change later after usage, then length of array will be still the same

How to count the frequency of each number in an array based on user input

i just started learning java and was hoping i could get some help on a logical problem im having. My goal is to as user to enter multiple numbers into an array. I then request the user to insert number from their initial input and print the frequency of that number compared to their first input. I have searched for some time and all the explanations are beyond my level so if anyone could reduce the explanation to a dummy level that will be great.
public class numberCounting {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[] storage = new int[100];
int counter = 0;
System.out.println("How many total enteries?");
int total = input.nextInt();
for (int i = 1; i <= total; i++) {
System.out.println("Enter the " + i + " number");
int entry = input.nextInt();
storage[i] = entry;
}
System.out.println("what number do you want to count the frequency of?: ");
int frequency = input.nextInt();
for (int x : frequency) {
if (x == x) {
counter++;
}
System.out.println("There are " + counter + "repeats of your number");
}
}
}

You are checking the wrong input and on top of that you are looping wrongly. Does it even compile? Change it to that
for (int x: storage) {
if (x == frequency) counter++;
}
Besides that - an array starts at the zero index. You are skipping the first entry by setting i = 1.

I have been asked to make an Create a new integer array with 16 elements

Java code (not Java script). I was asked to create a new integer array with 16 elements.
Only integers between 1 and 7 are to be entered in the array from user (scanner)input.
Only valid user input should be permitted, and any integers entered outside the bounds (i.e. < 1 or > 7 should be excluded and a warning message displayed.
Design a program that will sort the array.
The program should display the contents of the sorted array.
The program should then display the numbers of occurrences of each number chosen by user input
however i have been trying to complete this code step by step and used my knowledge to help me but need help my current code is under I would appreciate if some one is able to edit my code into the above wants.I know it needs to enter the array by user input store and reuse the code to sort the numbers into sort the array.
The result should print out something like this like this
“The numbers entered into the array are:” 1, 2,4,5,7
“The number you chose to search for is” 7
“This occurs” 3 “times in the array”
import java.util.Scanner;
public class test20 {
public static void main (String[] args){
Scanner userInput = new Scanner (System.in);
int [] nums = {1,2,3,4,5,6,7,6,6,2,7,7,1,4,5,6};
int count = 0;
int input = 0;
boolean isNumber = false;
do {
System.out.println ("Enter a number to check in the array");
if (userInput.hasNextInt()){
input = userInput.nextInt();
System.out.println ("The number you chose to search for is " + input);
isNumber = true;
}else {
System.out.println ("Not a proper number");
}
for (int i = 0; i< nums.length; i++){
if (nums [i]==input){
count ++;
}
}
System.out.println("This occurs " + count + " times in the array");
}
while (!(isNumber));
}
private static String count(String string) {
return null;
}
}

import java.util.Scanner;
import java.util.Arrays;
public class test20 {
private static int readNumber(Scanner userInput) {
int nbr;
while (true) {
while(!userInput.hasNextInt()) {
System.out.println("Enter valid integer!");
userInput.next();
}
nbr = userInput.nextInt();
if (nbr >= 1 && nbr <= 7) {
return nbr;
} else {
System.out.println("Enter number in range 1 to 7!");
}
}
}
private static int count(int input, int[] nums) {
int count = 0;
for (int i = 0; i < nums.length; i++){
if (nums[i] == input){
count++;
} else if (nums[i] > input) {
break;
}
}
return count;
}
public static void main(String[] args) {
Scanner userInput = new Scanner(System.in);
int[] nums = new int[16];
for (int i = 0; i < nums.length; i++) {
nums[i] = readNumber(userInput);
}
Arrays.sort(nums);
System.out.println ("Sorted numbers: " + Arrays.toString(nums));
int input = 0;
while(true) {
System.out.println("Search for a number in array");
input = readNumber(userInput);
System.out.println("The number you chose to search for is " + input);
System.out.println("This occurs " +
count(input, nums) + " times in the array");
}
}
}
Because the array is sorted, I break the loop if an element larger than the one we're looking for is found; if we encounter a larger one then no other matches can be found in the rest of the array.

Arrays with user input

I am trying to write a program that repeatedly asks the user to supply scores (out of 10) on a test.It needs to continue until a negative value is supplied. Values higher than 10 should be ignored. I also calculated the average of the inputs. After the scores have been inputted, i need to use a single array to produce a table that automatically fills the test scores and the number of occurrences of the certain test score.
I wanted it to look something like this:
Score | # of Occurrences
0 3
1 2
2 4
3 5
4 6
and so on.. P
I am a beginner and this is my first question, so i am sorry if i made a mistake in posting the question or something.
import java.io.*;
import java.util.*;
public class Tester1
{
public static void main()
{
Scanner kbReader= new Scanner (System.in);
int score[] = new int [10];//idk what im doing with these two arrays
int numofOcc []= new int [10];
int counter=0;
int sum=0;
for (int i=0;i<10;i++)// Instead of i<10... how would i make it so that it continues until a negative value is entered.
{
System.out.println("Enter score out of 10");
int input=kbReader.nextInt();
if (input>10)
{
System.out.println("Score must be out of 10");
}
else if (input<0)
{
System.out.println("Score must be out of 10");
break;
}
else
{
counter++;
sum+=input;
}
}
System.out.println("The mean score is " +(sum/counter));
}
}

You could use a do...while loop like this:
import java.io.*;
import java.util.*;
public class Tester1
{
public static void main(String args[]) {
Scanner kbReader= new Scanner (System.in);
int scores[] = new int [10];
int counter = 0;
int sum = 0;
int input = 0;
do {
System.out.println("Enter score out of 10 or negative to break.");
input=kbReader.nextInt();
if (input<0) {
break;
} else if (input>10) {
System.out.println("Score must be out of 10");
} else {
scores[input]++;
counter++;
sum+=input;
}
} while (input>0);
System.out.println("Score\t# of occur...");
for(int i =0; i<10; i++) {
System.out.println(i + "\t" + scores[i]);
};
System.out.println("The mean score is " +(sum/counter));
}
}
The formatting can certainly be done better (without c-style tabs) but I don't remember the syntax at the moment.

I think what you need is a List Array! Create ArrayList from array
Think of it as a dynamic array, you don't need to specify the size of the array and it is expanded/made smaller automatically.

What you're missing is a while loop. Here is a nice way to loop through a Scanner for input. It also catches numbers greater than 10 and provides an error message:
public static void main() {
Scanner s = new Scanner(System.in);
ArrayList<Integer> list = new ArrayList<Integer>();
int response = 0;
while (response >= 0) {
System.out.print("Enter score out of 10: ");
response = s.nextInt();
if (response > 10) {
System.out.println("Score must be out of 10.");
} else if (response >= 0) {
list.add(response);
}
}
// Do something with list
}