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Having problems utilizing Arrays and for loops in a Java assignment

The program asks to "write a Java program that will first ask the user how many grades they want to enter. Then use a do..while loop to populate an array of that size with grades entered by the user. Then sort the array. In a for loop read through that array, display the grades and total the grades. After the loop, calculate the average of those grades and display that average."
The output is the issue. No matter what I do with the code, it will only output two of the inputs I have typed. If I chose to enter 4,5, or 10 grades. It will only show the lowest two. Although the total and the averages are correct. What is it that I am missing here?
Here is what I have written:
import java.util.Scanner;
import java.util.Arrays;
public class TapCoGradeArray
{
public static void main(String[] args)
{
Scanner keyboard = new Scanner(System.in);
int count;
double inputGrade = 0;
double gradeTotal = 0;
double[] individualGrade;
System.out.println("Enter the number of students that are being graded.");
int numberOfGrades = keyboard.nextInt();
individualGrade = new double[numberOfGrades];
count = 0;
do
{
System.out.println("Enter the grade (from 0-100) for each student below.");
inputGrade = keyboard.nextDouble();
individualGrade[count] = inputGrade;
count++;
gradeTotal+= inputGrade;
} while(count < numberOfGrades);
Arrays.sort(individualGrade);
for(count = 0; count == individualGrade.length; count++);
{
// This next line is using gradeTotal as an array. However, there is no array by that name.
// Check which array this should be.
System.out.println("The grades entered are the following: \n" + inputGrade + "\n" + individualGrade[count]);
}
double gradeAverage = gradeTotal / numberOfGrades;
System.out.println("The total of the grades is " + gradeTotal);
System.out.println("The average of the grades entered is " + gradeAverage);
}
}

Two main problems
for(count = 0; count == individualGrade.length; count++);
this should not have a seimcolon and looping until this values is reached is correct.
for(count = 0; count < individualGrade.length; count++)
{
System.out.println("The grades entered are the following: \n" +
inputGrade + "\n" + individualGrade[count]);
}

Java average program with any number of inputs

What I'm trying to make is an averaging program that takes any number of inputs. So far I need to have the user specify how many numbers they want to average, and if they don't give that many numbers the program crashes. Is there any way that I could just have them put as many numbers as they want and afterwards the array length is set?
Here is the code I am using right now:
import java.util.*;
public class Average_any
{
public static void main (String[] args) {
Scanner scan = new Scanner (System.in);
System.out.println ("How many numbers do you want to enter?");
final int ARRAY_LENGTH = scan.nextInt();
System.out.println ("Please type the numbers you want to find the average of, "
+ "and then type \"Done\".");
System.out.println ("Warning: Only type the exact amount of numbers that you specified.");
// If user doesn't enter same number, results in crash
double[] numbers = new double [ARRAY_LENGTH];
do {
for (int i = 0; i < numbers.length; i++) {
while (!scan.hasNextInt()) {
System.out.println("That's not a number!");
scan.next(); //Need this to enter another input
}
numbers[i] = scan.nextInt();
}
} while (!scan.hasNext("Done"));
double total = 0;
for (int i = 0; i < numbers.length; i++) {
total += numbers[i];
}
double average = total/ARRAY_LENGTH;
System.out.println ("Your average is: " + average);
}
}
(Just in case anyone is wondering, no this is not a school assignment, I was just wondering because we did a simpler version in school)

Take the array out of the equation altogether
Scanner scan = new Scanner (System.in);
double total = 0;
int count = 0;
while (scan.hasNextDouble()) {
total += scan.nextDouble();
count ++;
}
double average = total / count;

I am getting error messages concerning my coding. I know Scanf is not a java function, so I am hoping to get help converting it

I know that scanf is not a java function, so i'm hoping someone can help me to understand how to convert this. Research on this topic is difficult to piece together.
This is my code:
import java.util.Scanner;
public class Average {
Scanner Scanner = new Scanner (System.in);
int main (){
int counter;
int number;
int total;
float average;
total = 0;
counter = 0;
System.out.println("Enter the number 0 to end: ");
Scanf("%d", &number);
While (number != 0) {
total = total + number;
counter = counter + 1;
System.out.println("Enter the number 0 to end: ");
Scanf("%d", &number);
}
if(counter != 0) {
average = (float) total / counter;
System.out.println("Average is %.2f\n", average);
} else {
System.out.println("No valid numbers have been entered.");
return 0;
}
}
}

use input like this`
public class seting{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);`
int total = 0;
System.out.printlnln("Enter the value of total :");
total = scan.nextInt(); // use integer input
}
}

You cannot use the same name for the object as for the class. Change Scanner initialization as follows:
Scanner scanObj = new Scanner(System.in);
Replace all your scanf statements with the below:
number = scanObj.nextInt();

These are the changes done to your code:
import java.util.Scanner;
public class one {
public static void main(String[] args) {
Scanner Scanner = new Scanner (System.in);
int counter;
int number = 1;
int total;
float average;
total = 0;
counter = 0;
while(number != 0){
System.out.println("Enter the number 0 to end: ");
number = Scanner.nextInt();
System.out.printf("%d", number);
total = total + number;
counter = counter + 1;
}
if(counter != 0){
average = ((float)total /(float)counter);
System.out.printf("Average is %.2f\n", average);
}
else{
System.out.println("No valid numbers have been entered.");
//return 0;
}
}
}
First the Scanner takes the value the user entered. number = Scanner.nextInt(); This must be done inside your while loop since its the one that check the condition.
The next thing I changed was average = (float) total / counter;
This casts the total value only to a float. use brackets to both ends.
average = ((float)total /(float)counter); like this

While loop not working

Hi I am fairly new to java and trying to familiarize myself to it by doing some exercises online.
How do i properly code the while loop so that everytime the user input is wrong it asks the same question again and does not proceed to the next line of code
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Array {
public static void main(String[] args) {
Scanner dataIn = new Scanner(System.in);
int entries = 0;
List<Integer> grade = new ArrayList<Integer>();
System.out.println("Enter number of students? ");
entries = dataIn.nextInt();
boolean checker = true;
while (checker){
for (int i = 0; i < entries; i++){
int input;
int addToList;
System.out.println("Enter grade for student: ");
input = dataIn.nextInt();
grade.add(input);
if (input >= 0 && input<= 100) {
}else {
System.out.println("invalid input try again..");
checker = false;
}
}
}
int sum = 0;
int count = grade.size();
double mean;
for (int grades : grade){
sum+= grades;
}
mean =(double)sum/count;
System.out.println("The Grades are: " + grade);
System.out.println("The number of elements in the Array is " + grade.size());
System.out.println("The average is: " + mean);
}
}

Your logic is backwards. You want the loop to continue if the input is incorrect. There are two ways to fix this:
Change while(checker) to while(!checker)
Change checker=false to checker=true after printing the error message. And set checker=false in the if branch.
It might help if you change the name of your checker variable to something that reads more directly. For example isInputCorrect reads very nicely when you write while(!isInputCorrect) and it also makes it more clear what the values of true and false represent.

try this :
boolean checker = true
for(int i=0;i< entries;i++){
int input;
System.out.println("Enter grade for student: ");
input = dataIn.nextInt();
while(checker){
if(input >= 0 && input<= 100){
grade.add(input);
checker = false;
}else{
System.out.println("invalid input try again..");
}
}
checker = true;
}

You could try this
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Array {
public static void main(String[] args) {
Scanner dataIn = new Scanner(System.in);
int entries = 0;
List<Integer> grade = new ArrayList<Integer>();
System.out.println("Enter number of students? ");
entries = dataIn.nextInt();
for (int i = 0; i < entries; i++) {
int input;
do{
input = dataIn.nextInt();
if (input >= 0 && input <= 100) {
grade.add(input);
}else{
System.out.println("invalid input try again..");
}
}while(!(input >= 0 && input <=100));
}
dataIn.close();
int sum = 0;
int count = grade.size();
double mean;
for (int grades : grade) {
sum += grades;
}
mean = (double) sum / count;
System.out.println("The Grades are: " + grade);
System.out.println("The number of elements in the Array is " + grade.size());
System.out.println("The average is: " + mean);
}
}

instead of doing while(checker)
make a loop for while(running)
then send it to the keyboard.nextInt()
if its the wrongAnswer than it will loop, if its correct than set running to false
and have code that follows the while loop

how to allow predefined amount of entries to java program

My program allows the user to enter 20 entries. each entry is entered as one entry then presses enter from command line. I would like to add the ability for the program to say
"you have 20 entries left"
then
"you have 19 entries left"
and so on... as the user enters more data in to the program.
I would appreciate if someone could show me the simplest way to add this to my current code.
import java.util.ArrayList;
import java.util.Scanner;
class project02Diaz
{
private static Double calculate_average( ArrayList<Double> myArr )
{
Double sum = 0.0;
for (Double number: myArr)
{
sum += number;
}
return sum/myArr.size();
}
public static void main( String[] args )
{
Scanner scan = new Scanner(System.in);
ArrayList<Double> myArr = new ArrayList<Double>();
int count = 0;
System.out.println("Enter one number at a time be averaged, you have 20 entries remaining:");
for (String inputs = scan.nextLine() ; !inputs.matches("[qQ]") ; inputs = scan.nextLine())
{
if (count == 20)
{
System.out.println("You entered more than 20 numbers, you suck!");
break;
}
try{
myArr.add(Double.valueOf(inputs));
count++;
System.out.println("Please enter another number or press Q for your average");
}
catch (NumberFormatException e) {
System.out.println("Try again you tard! You entered more than one number, or not a valid number at all.");
continue;
}
}
Double average = calculate_average(myArr);
System.out.println("Your average is: " + average);
}
}

You again! Allright, going to do that one, too. There isn't too much that you have to change: simply count your counter down from twenty and output it's stauts every time. Also, stop if you reach 0.
public static void main( String[] args )
{
Scanner scan = new Scanner(System.in);
ArrayList<Double> myArr = new ArrayList<Double>();
int entriesLeft = 20; // changed counter that counts upwards to one counting down.
System.out.println("Enter one number at a time be averaged, you have 20 entries remaining:");
// added additional condition to be checked: we now also stop if maximum number of entries ie reached.
for (String inputs = scan.nextLine() ; entriesLeft > 0 && !inputs.matches("[qQ]") ; inputs = scan.nextLine())
{
try{
myArr.add(Double.valueOf(inputs));
entriesLeft--; //counting one down
System.out.println("Please enter another number or press Q for your average");
// telling user how much numbers are left
System.out.println("You have " + entriesLeft + "numbers left.");
}
catch (NumberFormatException e) {
System.out.println("Try again you tard! You entered more than one number, or not a valid number at all.");
continue;
}
}
Double average = calculate_average(myArr);
System.out.println("Your average is: " + average);
}
Note that appending the integer entriesLeft to the string isn't super efficient, the nicer way is to call Integer.toString(entriesLeft).

import java.util.ArrayList;
import java.util.Scanner;
class project02Diaz
{
private static Double calculate_average( ArrayList<Double> myArr )
{
Double sum = 0.0;
for (Double number: myArr)
{
sum += number;
}
return sum/myArr.size();
}
public static void main( String[] args )
{
Scanner scan = new Scanner(System.in);
ArrayList<Double> myArr = new ArrayList<Double>();
int count = 0;
System.out.println("Enter one number at a time be averaged, you have 20 entries remaining:");
for (String inputs = scan.nextLine() ; !inputs.matches("[qQ]") ; inputs = scan.nextLine())
{
System.out.println("You have "+ String.valueOf(20 - count -1) +" number of enteries left");
if (count == 19)
{
System.out.println("You entered more than 20 numbers, you suck!");
break;
}
try{
myArr.add(Double.valueOf(inputs));
count++;
System.out.println("Please enter another number or press Q for your average");
}
catch (NumberFormatException e) {
System.out.println("Try again you tard! You entered more than one number, or not a valid number at all.");
continue;
}
}
Double average = calculate_average(myArr);
System.out.println("Your average is: " + average);
}
}