Finding the mode of an array from user input java

Finding the mode of an array from user input java - java

So I'm making a program that gets an array from user-inputed values but I'm having trouble writing the code for finding the mode of the array. I tried writing my own code and then tried using a version of someone else's code but that didn't work out because I didn't fully understand it to be honest.
import java.util.Scanner;
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
int length;
Statistics stats = new Statistics();
System.out.println("Welcome to our statistics program!");
System.out.print("Enter the amount of numbers you want to store: ");
length=Integer.parseInt(keyboard.next());
int[] nums = new int[length];
for(int i=0; i<length; i++) {
System.out.println("Enter a number: ");
nums[i]=keyboard.nextInt();
}
System.out.println("Array elements are: ");
for (int i=0; i<length; i++) {
System.out.println(nums[i]);
}
public int Mode (int[] nums) {
double maxValue = -1.0d;
int maxCount = 0;
for(int i = 0; i < data.length; i++) {
double currentValue = data[i];
int currentCount = 1;
for(int j = i + 1; j < data.length; ++j) {
if(Math.abs(data[j] - currentValue) < epsilon) {
++currentCount;
}
}
}
if (currentCount > maxCount) {
maxCount = currentCount;
maxValue = currentValue;
} else if (currentCount == maxCount) {
maxValue = Double.NaN;
}
}
System.out.println("The minimum number is " + stats.Mode(nums));

You could consider using a HashMap to maintain the frequencies of the values in the array in your loop:
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
public static int getIntegerInput(String prompt, Scanner scanner) {
System.out.print(prompt);
int validInteger = -1;
while (scanner.hasNext()) {
if (scanner.hasNextInt()) {
validInteger = scanner.nextInt();
break;
} else {
System.out.println("Error: Invalid input, try again...");
System.out.print(prompt);
scanner.next();
}
}
return validInteger;
}
public static int getPositiveIntegerInput(String prompt, Scanner scanner) {
int num = getIntegerInput(prompt, scanner);
while (num <= 0) {
System.out.println("Error: Integer must be positive.");
num = getIntegerInput(prompt, scanner);
}
return num;
}
public static int getMode(int[] nums) {
if (nums.length == 0) {
throw new IllegalArgumentException("nums cannot be empty");
}
Map<Integer, Integer> valueFrequencies = new HashMap<>();
valueFrequencies.put(nums[0], 1);
int maxFreq = 1;
int candidateMode = nums[0];
for (int i = 1; i < nums.length; i++) {
int value = nums[i];
valueFrequencies.merge(value, 1, Integer::sum);
int candidateFreq = valueFrequencies.get(value);
if (candidateFreq > maxFreq) {
candidateMode = value;
maxFreq = candidateFreq;
}
}
return candidateMode;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int numsLength = getPositiveIntegerInput("Enter how many numbers you want to store: ", scanner);
int[] nums = new int[numsLength];
for (int i = 0; i < numsLength; i++) {
nums[i] = getIntegerInput(String.format("Enter number %d: ", i + 1), scanner);
}
int mode = getMode(nums);
System.out.printf("Mode: %d%n", mode);
}
}
Example Usage:
Enter how many numbers you want to store: 0
Error: Integer must be positive.
Enter how many numbers you want to store: 6
Enter number 1: 3
Enter number 2: 2
Enter number 3: 5
Enter number 4: 5
Enter number 5: 3
Enter number 6: 3
Mode: 3

Related

Int array pushed through while loop until it reaches -1

I have to take a single line of user input, and calculate the average of all the numbers until it reaches -1 using a while loop. An example of user input could be something like 2 -1 6 which is why I've done it this way. I've figured out how to split this into an int array, but I can't figure out how to do the while loop portion.
System.out.println("user input")
String user = scan.nextLine();
String[] string = user.split(" ");
int[] numbers = new int[string.length];
for(int i = 0;i < string.length;i++) {
numbers[i] = Integer.parseInt(string[i]);
}
while ( > -1){
}

Class java.util.Scanner has methods hasNextInt and nextInt.
import java.util.Scanner;
public class Averages {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter series of integers on single line separated by spaces.");
System.out.println("For example: 2 -1 6");
int sum = 0;
int count = 0;
while (scan.hasNextInt()) {
int num = scan.nextInt();
if (num == -1) {
break;
}
sum += num;
count++;
}
if (count > 0) {
double average = sum / (double) count;
System.out.println("Average: " + average);
}
else {
System.out.println("Invalid input.");
}
}
}
Note that you need to cast count to a double when calculating the average otherwise integer division will be performed and that will not give the correct average.

I am assuming you mean, when user input number is -1. we should take average of all number before -1. that is was I am doing here.
System.out.println("user input")
String user = scan.nextLine();
int totalSum = 0;
double avg = 0;
String[] string = user.split(" ");
int[] numbers = new int[string.length];
for(int i = 0;i < string.length;i++) {
numbers[i] = Integer.parseInt(string[i]);
if(numbers[i]==-1){
avg = (double)totalSum / i;
break;
}
totalSum += numbers[i];
}
With only while loop
System.out.println("user input");
String user = scan.nextLine();
int totalSum = 0;
double avg = 0;
String[] string = user.split(" ");
int[] numbers = new int[string.length];
int i = 0;
numbers[i] = Integer.parseInt(string[i]);
while(numbers[i]!=-1) {
totalSum += numbers[i];
i++;
numbers[i] = Integer.parseInt(string[i]);
}
avg = (double)totalSum / i;

import java.util.Scanner;
public class Main
{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("user input");
String user = scan.nextLine();
boolean found = false;
Double average = 0.0;
String[] string = user.split(" ");
int[] numbers = new int[string.length];
for(int i = 0;i < string.length && found == false ;i++) {
numbers[i] = Integer.parseInt(string[i]);
}
int t = 0;
while (found == false && t < string.length){
if(numbers[t] == - 1){
average = average/t;
found = true;
}
else{
average = (Double) average + numbers[t];
t++;
}
}
System.out.println("Average = " + average);
}
}

Java: How to use binary search with an array

For this java program, I'm trying to use a binary search for the array I have created in the Class Numbers, however, when I enter the 4th choice, the program just ends. The method binSearch is in Class Numbers. I can enter the required the size of the array, generate random numbers, search for specific numbers, and display them. However, when I want to use a binary search, the program ends as previously said. What is the reason why the program ends and what needs to be done to fix that certain method?
public class Numbers {
int[] array;
private int sizeOfArray;
public Numbers() {
sizeOfArray = 0;
array= new int [sizeOfArray];
}
public Numbers(int sizeOfArray) {
this.sizeOfArray = sizeOfArray;
array= new int [sizeOfArray];
}
public void generateNumbers() {
Random randomNumber = new Random();
int theNumber = 0;
for (int i = 0; i < sizeOfArray; i++) {
theNumber = randomNumber.nextInt(50);
array[i] = theNumber;
}
}
public int count(int num) {
int theNumbers = 0;
for (int i = 0; i < sizeOfArray; i++) {
if (array[i] == num) {
theNumbers++;
}
}
return theNumbers;
} // end count method
public String toString() {
String myArray = "";
for (int i = 0; i < sizeOfArray; i++) {
myArray += array[i] + " ";
}
return myArray;
}
public int binSearch(int[] array, int key) {
int low = 0;
int high = sizeOfArray - 1;
//int middle = (low + high + 1) /2;
int location = -1;
while (high >= low) {
int middle1 = (low + high) / 2;
if (array[middle1] == key ) {
//return true;
}
if (array[middle1] < key) {
low = middle1 + 1;
}
if (array[middle1] > key) {
high = middle1 - 1;
}
}
//return false;
return location;
}
}
and here is the main menu:
boolean isDone = false;
String input = null;
Numbers theNumber = new Numbers();
Scanner scanner = new Scanner (System.in);
try {
while (isDone == false) {
/*Menu options */
System.out.println("Enter 1 to create array size");
System.out.println("Enter 2 to generate random numbers");
System.out.println("Enter 3 to search and display number of occurrences");
System.out.println("Enter 4 to binary search to find whether specific number exists");
System.out.println("Enter 5 to display the array");
System.out.println("Enter 6 to quit the program");
input = scanner.nextLine();
switch (input) {
case "1":
int intNumber1 = 0;
System.out.println("Enter required size:");
intNumber1 = Integer.valueOf(scanner.nextLine());
theNumber = new Numbers(intNumber1);
System.out.println("Array has been generated.");
break;
case "2":
//theNumber = new Numbers();
theNumber.generateNumbers();
System.out.println("Numbers have been generated and stored.");
break;
case "3":
int intNumber2 = 0;
System.out.println("Enter number to search for: ");
intNumber2 = Integer.valueOf(scanner.nextLine());
System.out.println("Number of occurences of " + intNumber2 + " in the array is " + theNumber.count(intNumber2) + ".");
break;
case "4":
int key = 0;
theNumber.binSearch(null, key);
System.out.println("Array is sorted: ");
break;
case "5":
int theNumbers = 0;
if (theNumbers == 0)
{
System.out.println("No array has not been generated yet.");
}
else
{
System.out.println("The numbers are: ");
}
System.out.println(theNumber.toString());
break;
case "6":
isDone = true;
System.out.println("Bye... See you again");
scanner.close();
break;
default:
System.out.println("These are invalid choices...please reenter.");
break;
}
}
}
catch (Exception exception)
{
System.out.println("This is an invalid choice...please reenter.");
scanner.nextLine();
return;
}

Error when transferring code

I'm writing code for class, and the code works fine when I run it in Dr. Java in class. However when I input it for grading, I get an error that reads:
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at Main.main(Main.java:247)
at Ideone.assertRegex(Main.java:94)
at Ideone.test(Main.java:42)
at Ideone.main(Main.java:29)
I have no idea what this means, we haven't covered this sort of thing and I am not a very experienced programmer, sorry. My code is as follows;
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int indexFirst = 0;
int indexSecond = 0;
int[] first = new int[10000];
int[] second = new int[10000];
System.out.println("Enter the values for the first array, up to 10000 values, enter a negative number to quit");
do {int value = scanner.nextInt();
if (value < 0) {
break;
}
first[indexFirst++] = value;
} while(true);
System.out.println("Enter the values for the second array, up to 10000 values, enter a negative number to quit");
do {int value = scanner.nextInt();
if (value <= 0) {
break;
}
second[indexSecond++] = value;
} while(true);
System.out.println("First Array:");
for (int i = 0; i < indexFirst; i++) {
System.out.print(first[i] + " ");
}
System.out.println("\n");
System.out.println("Second Array:");
for (int i = 0; i < indexSecond; i++) {
System.out.print(second[i] + " ");
}
System.out.println("\n");
for (int i = 1; i < indexFirst; i++) {
if (first[i-1] > first[i] ) {
System.out.println("ERROR: Array not in correct order");
return;
}
}
for (int i = 1; i < indexSecond; i++) {
if (second[i-1] > second[i] ) {
System.out.println("ERROR: Array not in correct order");
return;
}
}
int[] merged = new int[indexFirst + indexSecond];
int curIdx1 = 0;
int curIdx2 = 0;
for(int mergedIdx = 0; mergedIdx < merged.length; mergedIdx++) {
if (curIdx2 == indexSecond) {
merged[mergedIdx] = first[curIdx1++];
} else if (curIdx1 == indexFirst) {
merged[mergedIdx] = second[curIdx2++];
} else if (first[curIdx1] < second[curIdx2]) {
merged[mergedIdx] = first[curIdx1++];
} else {
merged[mergedIdx] = second[curIdx2++];
}
}
System.out.println("Merged Array:");
for (int i = 0; i < merged.length; i++) {
System.out.print(merged[i] + " ");
}
}
}
If anyone has any input on how to fix this, it would be much appreciated.

To check if a number is Armstrong number using java

this is my program:
public class ArmstrongNumber {
public static void main(String args[]) {
int n = 0, temp = 0, r = 0, s = 0;
Scanner in = new Scanner(System.in);
System.out.println("Enter a number ");
if (in.hasNextInt()) {
n = in.nextInt(); // if there is another number
} else {
n = 0;
}
temp = n;
while (n != 0) {
r = n % 10;
s = s + (r * r * r);
n = n / 10;
}
if (temp == s) {
System.out.println(n + " is an Armstrong Number");
} else {
System.out.println(n + " is not an Armstrong Number");
}
}
}
output:
Exception in thread "main" java.lang.NoClassDefFoundError
I tried it using DataInputStream but still getting same error.

// To check the given no is Armstrong number (Java Code)
class CheckArmStrong{
public static void main(String str[]){
int n=153,a, b=0, c=n;
while(n>0){
a=n%10; n=n/10; b=b+(a*a*a);
System.out.println(a+" "+n+" "+b); // to see the logic
}
if(c==b) System.out.println("Armstrong number");
else System.out.println(" Not Armstrong number");
}
}

Find any digit is Armstrong number or not using loop
for(int arm_num = 0 ; arm_num < 100000 ; arm_num++)
{
String[] data = String.valueOf(arm_num).split("(?<=.)");
int lngth = String.valueOf(arm_num).length();
int arm_t_num = 0;
int ary[] = new int[lngth];
for(int i = 0 ; i < lngth ; i++)
{
ary[i] = Integer.parseInt(data[i]);
for(int x = 0 ; x < lngth-1 ; x++)
{
ary[i] = ary[i] * Integer.parseInt(data[i]);
}
arm_t_num+=ary[i];
}
if(arm_num == arm_t_num)
{
System.out.println("Number is ArmStrong : "+arm_num);
}
}

you need to set CLASS_PATH variable and point it to where ever your class file is
then this should work
I have tried it locally, refer my answer to check how to set class path and how to compile and run java code using command prompt

//This is my program to check whether the number is armstrong or not!!
package myprogram2;
public class Myprogram2 {
public static void main(String[] args)
{
String No="407";
int length_no=No.length();
char[] S=new char[length_no];
int[] b = new int[length_no];
int arm=0;
for(int i=0;i<length_no;i++)
{
S[i]=No.charAt(i);
b[i]=Character.getNumericValue(S[i]);
//System.out.print(b[i]);
arm=arm + (b[i]*b[i]*b[i]);
System.out.println(arm);
}
//System.out.println(" is the number \n now Checking for its Armstrong condition");
int orgno = Integer.parseInt(No);
if (orgno==arm)
System.out.println("YESm its an armstrong");
else
System.out.println("\n<<Not an armstrong>>");
//System.out.println(length_no);
System.out.println("Original number is "+orgno);
System.out.println("Sum of cubes "+arm);
}
}

There are a couple of nice String-based solutions and numeric solutions with single-letter variable names.
Consider this to make sense of how it works numerically, which includes a couple of interesting numeric tricks:
import java.io.*;
public class Armstrong
{
public static void main(String args[]) throws IOException
{
InputStreamReader read = new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(read);
int modifiedNumber, originalNumber, modifiedNumberWithUnitsDigitZero,
unitsDigit, runningSum;
System.out.println("Enter your number:");
modifiedNumber = Integer.parseInt(in.readLine());
runningSum = 0;
originalNumber = modifiedNumber;
while(modifiedNumber > 0)
{
modifiedNumberWithUnitsDigitZero = modifiedNumber / 10 * 10;
unitsDigit = modifiedNumber - modifiedNumberWithUnitsDigitZero;
runningSum += unitsDigit * unitsDigit * unitsDigit;
modifiedNumber = modifiedNumber / 10;
}
System.out.println("The number " + originalNumber
+ (originalNumber == runningSum ? " IS" : " is NOT")
+ " an Armstrong number because sum of cubes of digits is " + runningSum);
}
}

import java.util.Scanner;
public class Amst {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter The No. To Find ArmStrong Check");
int i = sc.nextInt();
int sum = 0;
for(int j = i; j>0 ; j = j/10){
sum = sum + ((j%10)*(j%10)*(j%10));
}
if(sum == i)
System.out.println("Armstrong");
else
System.out.println("Not Armstrong");
}
}

For 'N' digit amstrong number
package jjtest;
public class Amstrong {
public static void main(String[] args) {
// TODO Auto-generated method stub
int num=54748;
int c=0;
int temp=num;
int b=1;
int length = (int)(Math.log10(num)+1);
while(num>0){
int r = num%10;
num=num/10;
int a =1;
for(int i=1;i<=length;++i){
b=b*r;
}
c = c + b;
b=1;
}
System.out.println(c);
if(c==temp){
System.out.println("its an amstrong number");
}else{
System.out.println("its not an amstrong number");
}
}
}

This is the simple logic for Armstrong number program :
for (int i = number; i > 0; i = i / 10)
{
remainder = i % 10;
sum = sum + remainder * remainder * remainder;
}
if(sum == number)
{
System.out.println("\n" + number + " is an Armstrong Number\n");
}
Reference :
http://topjavatutorial.com/java/java-programs/java-program-to-check-if-a-number-is-armstrong-number/

import java.util.Scanner;
/* a number is armstrong if the sum of cubes if individual digits of
a number is equal to the number itself.for example, 371 is
an armstrong number. 3^3+7^3+1^3=371.
some others are 153,370,407 etc.*/
public class ArmstrongNumber {
public static void main(String args[]) {
int input, store, output=0, modolus;
Scanner in = new Scanner(System.in);
System.out.println("Please enter a number for ckecking.");
input = in.nextInt();
store = input;
while(input != 0) {
modolus = input % 10;
output = output + (modolus * modolus * modolus);
input = input / 10;
}
System.out.println(output);
if(store == output) {
System.out.println("This is an armstrong number.");
} else {
System.out.println("This is not an armstrong number.");
}
in.close();
}
}

import java.util.*;
public class ArmstrongNumber
{
public static void main( String[] args )
{
int n = 0, temp = 0, r = 0, s = 0;
Scanner in = new Scanner(System.in);
System.out.println("Enter a number ");
if (in.hasNextInt()) {
n = in.nextInt(); // if there is another number
} else {
n = 0;
}
temp = n;
while (n != 0) {
r = n % 10;
s = s + (r * r * r);
n = n / 10;
}
if (temp == s) {
System.out.println(temp + " is an Armstrong Number");
} else {
System.out.println(temp + " is not an Armstrong Number");
}
}
}
You missed to import java.util package
Change n to temp in S.O.P

import java.util.Scanner;
public class AmstrongNumber {
public static void main(String[] args) {
System.out.println("Enter the number");
Scanner scan=new Scanner(System.in);
int x=scan.nextInt();
int temp2=0;
String s1 = Integer.toString(x);
int[] a = new int[s1.length()];
int[] a1 = new int[s1.length()];
for (int i = 0; i < s1.length(); i++){
a[i] = s1.charAt(i)- '0';
int temp1=a[i];
a1[i]=temp1*temp1*temp1;
}
for (int i = 0; i < s1.length(); i++){
temp2=temp2+a1[i];
if(i==s1.length()-1){
if(x==temp2){
System.out.println("Amstrong num");
}else{
System.out.println("Not !");
}
}
}
}
}

private static boolean isArmstrong(int num) {
int totalSum = 0;
int copyNum = num;
while (num != 0) {
int reminder = num % 10;
int cubeOfReminder = reminder * reminder * reminder;
totalSum = totalSum + cubeOfReminder;
num = num / 10;
}
if (copyNum == totalSum)
return true;
return false;
}

public class Testamstrong
{
public static void main(String...strings) {
int num = 153,temp;
temp = num;
if(temp == amstrongNumber(num)) {
System.out.println("Number is amstrong number...");
}
else {
System.out.println("Number is not amstrong number...");
}
}
public static int amstrongNumber(int num) {
int count=0,sum=0;
count = String.valueOf(num).length();
char[] ch = String.valueOf(num).toCharArray();
for(char ch1:ch) {
int num1 = Character.getNumericValue(ch1);
sum += Math.pow(num1, count);
}
return sum;
}
}

Find Armstrong number using for loops (with example)
import java.util.*;
public class ArmstorngNumber {
public static void main(String args[]) {
int cube, num, quo, n;
int s = 0;
do
{
System.out.println("Enter Your Number");
Scanner sc = new Scanner(System.in);
num = sc.nextInt();//153
n = num;
for (int i = 0; i < 10; i++) {
int rem = num % 10;//3
quo = num / 10; //15
cube = rem * rem * rem;//9
s = s + cube;//0+9
num = quo;//0
}
System.out.println(s);
System.out.println(n);
if (s == n) {
System.out.println("The number is Armstrong");
System.out.println("-------------------------------------");
}
else {
System.out.println("The number is not Armstrong");
System.out.println("-------------------------------------");
}
}
while (n > 0);
}
}

Check the Armstrong number of any number [java] [Armstrong]
import java.util.*;
public class Armstrong {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("enter any number?");
int x = sc.nextInt();
int n=0;
int number = x;
int j =x;
int result = 0 ,remainder;
while (x!=0) {
x/=10;
++n;
}
for(;j>0 ;j=j/10) {
remainder=j%10;
result+=Math.pow(remainder, n);
}
if (number==result) {
System.out.print(number +" is Armstrong ");
}
else
System.out.print(number +" is not Armstrong");
}
}

here is my code, please check if this works for you!
import java.util.Scanner;
public class Armstromg {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Please enter the number: ");
int num = sc.nextInt();
int length = 0;
int temp1 = num;
while(temp1 != 0) {
temp1/=10;
length+=1;
}
int result = 1;
int temp2 = num;
for(int i = 1; i <= length; i++) {
temp2 = temp2 % 10;
result*=Math.pow(temp2,length);
}
if(result == num) {
System.out.print("The number is an armstrong number!");
} else {
System.out.print("The number is not an armstrong number");
}
}
}

package Loops;
public class ArmStrongNumber {
public static void main(String[] args) {
int digit1, digit2, digit3;
int number = 153;
int temp = number;
digit1 = number % 10;
number = number / 10;
digit2 = number % 10;
number = number / 10;
digit3 = number % 10;
if ((digit1 * digit1 * digit1) + (digit2 * digit2 * digit2) + (digit3 * digit3 * digit3) == temp) {
System.out.println(+temp + " Number is Armstrong ");
} else {
System.out.println("Number is not Armstrong");
}
}
}

//Not limited to 3 digit integers
public static void main(String[] args)
{
int num = 54748,a,sum=0;
int x = num;
int p =Integer.toString(num).length();
while (num !=0)
{
a = num%10;
num = num/10;
sum = sum + (int) Math.pow(a, p);
}
if (x==sum)
System.out.println("Its an Armstrong number");
else
System.out.println("Not an Armstrong number");
}
}

Scanner input = new Scanner (System.in);
int num , counter = 0 ,temp;
System.out.print("Enter Nmber :");
num = input.nextInt();
int lnum = num;
while ( num != 0 ){
num = num/10 ;
counter++;
}
int store_num_keyboard_input = lnum;
int new_tot = 0;
int c = counter;
while(lnum > 0){
temp = lnum % 10;
lnum = lnum / 10 ;
int m = 0; //m is counter
int tot = 1;
while (m != c){
tot = tot * temp;
m++;
}
new_tot = new_tot + tot;
}
System.out.println("new total "+ new_tot );
if(new_tot == store_num_keyboard_input){
System.out.println(store_num_keyboard_input + " is an Armstrong number" );
}
else{
System.out.println(store_num_keyboard_input + " is not an Armstrong number" );
}

My answer using JAVA 8
tested for..[1, 153, 370, 371, 407]
public class Armstrong {
public static boolean isArmstrong(int num) {
return num == getArmstrongSum(num);
}
public static int getArmstrongSum(int num) {
int pow = String.valueOf(num).length();
return IntStream.iterate(num, i -> i / 10)
.limit(pow)
.map(i -> (int) Math.pow(i % 10, 3))
.sum();
}
public static void main(String[] args) {
System.out.println(isArmstrong(153));
}
}
Thank you.

NoSuchElementException Java

This is a simple program that I wrote to do calculations on integers from a txt file. After a few hours of trying to debug, I was hoping a fresh set of eyes could spot a few of my problems. EDIT: data.txt contains integers 1-5. One integer per line.
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;
public class Calculator {
public static int[] NUMBERS; //global value for the array
public static void main(String[] args) throws FileNotFoundException {
File file = new File("data.txt");
Scanner sc = new Scanner(file);
List x = new ArrayList();
while (sc.hasNextInt()) {
x.add(sc.nextInt());
}
NUMBERS = new int[x.size()];
Iterator<Integer> iterator = x.iterator();
for (int i = 0; i < NUMBERS.length; i++) {
NUMBERS[i] = iterator.next().intValue();
}
sc.close();
Scanner sc2 = new Scanner(file);
System.out.println("Welcome to Calculation Program!\n");
startMenus(sc2);
}
private static void startMenus(Scanner sca) throws FileNotFoundException {
while (true) {
System.out.println("(Enter option # and press ENTER)\n");
System.out.println("1. Display the average of the list");
System.out.println("2. Display the number of occurences of a given element in the list");
System.out.println("3. Display the prime numbers in a list");
System.out.println("4. Display the information above in table form");
System.out.println("5. Save the information onto a file in table form");
System.out.println("6. Exit");
int option = sca.nextInt();
sca.nextLine();
switch (option) {
case 1:
infoMenu1(sca);
break;
case 2:
infoMenu2(sca);
break;
case 3:
infoMenu3(sca);
break;
case 4:
infoMenu4(sca);
break;
case 5:
infoMenu5(sca);
break;
case 6:
System.exit(0);
default:
System.out.println("Unrecognized Option!\n");
}
}
}
private static void infoMenu1(Scanner sc2) {
System.out.println("The average of the numbers in the file is: " + avg(NUMBERS));
}
public static double avg(int[] numbers) {
int sum = 0;
for (int i = 0; i < numbers.length; i++) {
sum = (sum + numbers[i]);
}
return (sum / numbers.length);
}
public static int occr(int[] numbers, int x) {
int count = 0;
for (int n : numbers) {
if (n == x) {
count = count + 1;
}
}
return count;
}
public static boolean prime(int x) {
boolean answer = true;
if (x == 0 || x == 1) {
return false;
}
for (int i = 2; i <= x / 2; i = i + 1) {
if (i != x) {
if (x % i == 0) {
answer = false;
}
}
}
return answer;
}
public static int[] primes(int[] numbers) {
int primesCount = 0;
for (int i : numbers) {
if (prime(i)) {
primesCount = (primesCount + 1);
}
}
if (primesCount == 0) {
return null;
}
int[] result = new int[primesCount];
int index = 0;
for (int i : numbers) {
if (prime(i)) {
result[index] = i;
index = index + 1;
}
}
return result;
}
private static void infoMenu2(Scanner sc) {
sc = new Scanner(System.in);
System.out.println("Which integer would you like to check for number of occurences?");
int choice = sc.nextInt();
System.out.println("The number of occurence(s) of " + choice + " are/is " + occr(NUMBERS, choice));
}
private static void infoMenu3(Scanner sc2) {
int[] myPrimes = primes(NUMBERS);
System.out.println("The prime number(s) in the file are/is: ");
for (int j = 0; j < myPrimes.length; ++j) {
System.out.println(myPrimes[j] + " ");
}
}
private static void infoMenu4(Scanner kb) throws FileNotFoundException {
File file = new File("data.txt");
Scanner sc = new Scanner(file);
int counter = 0;
while (sc.hasNextInt()) {
counter = counter++;
}
int lenth = counter;
int[] column1 = new int[lenth];
while (sc.hasNextInt()) {
column1 = new int[sc.nextInt()];
}
int[] column2 = new int[occr(NUMBERS, sc.nextInt())];
boolean column3 = prime(sc.nextInt());
System.out.printf("Average: " + "%20.2f", column1);
System.out.println();
System.out.printf("Occurences: " + "%14d", column2);
System.out.println();
System.out.printf("Primes:" + "%19s : %s", column3);
System.out.println();
}
private static void infoMenu5(Scanner kb) throws FileNotFoundException {
File file = new File("data.txt");
Scanner sc = new Scanner(file);
PrintWriter pw = new PrintWriter(new File("results.txt"));
int counter = 0;
while (sc.hasNextInt()) {
counter = counter++;
}
int lenth = counter;
int[] column1 = new int[lenth];
while (sc.hasNextInt()) {
column1 = new int[sc.nextInt()];
}
int[] column2 = new int[occr(NUMBERS, sc.nextInt())];
boolean column3 = prime(sc.nextInt());
pw.printf("Number: " + "%-10d", column1);
pw.println();
pw.printf("Occurences: " + "%12d", column2);
pw.println();
pw.printf("Primes:" + "%24s : %s", column3);
pw.println();
pw.close();
}
}

You are using wrong Scanner in your code (line 49). I suppose you are trying to get user input. However, you are using Scanner to get input from data.txt.
Updated according to the comments. Actually, you don't need Scanner from data.txt in startMenus. What you need is user input. So change sc2 to Scanner from System.in.
Original line 31:
// Scanner sc2 = new Scanner(file);
Scanner sc2 = new Scanner(System.in);

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