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Finding the mode of an array from user input 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

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);
}
}

Not able to generate all the Kaprekar Number in a range

Though the problem seemed simple, here it is :-
A Kaprekar number is a positive whole number n with d digits, such that when we split its square into two pieces - a right hand piece r with d digits and a left hand piece l that contains the remaining d or d−1 digits, the sum of the pieces is equal to the original number (i.e. l + r = n).
The Task
You are given the two positive integers p and q, where p is lower than q. Write a program to determine how many Kaprekar numbers are there in the range between p and q (both inclusive) and display them all.
Input Format
There will be two lines of input: p, lowest value q, highest value
Constraints:
0<p<q<100000
Output Format
Output each Kaprekar number in the given range, space-separated on a single line. If no Kaprekar numbers exist in the given range, print INVALID RANGE.
I could not clear the test cases in the range
22223
99999
In the above range the follwoing numbers should have been generated :-
77778 82656 95121 99999
Here is my code :-
import java.io.*;
import java.util.*;
public class Solution {
public static void main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
Scanner scan = new Scanner(System.in);
int p = scan.nextInt();
int q = scan.nextInt();
boolean exist = false;
if(q <= p){
System.out.println("INVALID RANGE");
}
int m = 0,n = 0;
long sqr = 0;
String numb = "";
String[] digits = new String[2];
for(int i = p; i <= q; i++){
if(i == 1)System.out.print(1 + " ");
else{
sqr = i*i;
numb = String.valueOf(sqr);// Changing it into a string.
if(numb.length() % 2 == 0){
digits[0] = numb.substring(0, numb.length()/2);//Splitting it into two parts
digits[1] = numb.substring(numb.length()/2);
}else{
digits[0] = numb.substring(0, (numb.length() - 1)/2);
digits[1] = numb.substring((numb.length() -1)/2);
}
if(digits[0] == "" )
m = 0;
if(digits[1] == "")
n = 0;
if(!digits[1].equals("") && !digits[0].equals("")){
m = Integer.parseInt(digits[0]);
n = Integer.parseInt(digits[1]);
}
if(i == (m + n) ){ //Testing for equality
System.out.print(i + " ");
exist = true;
}
}
}
if(exist == false){// If exist is never modified print Invalid Range.
System.out.println("INVALID RANGE");
}
}
}

import java.util.*;
public class Kaprekar
{
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter a number");
int num=sc.nextInt();
int sq=num*num; String sq1=Integer.toString(sq);
int mid=(Integer.toString(sq).length())/2;
int rem=sq%((int)Math.pow(10,sq1.length()-mid));
int quo=sq/((int)Math.pow(10,sq1.length()-mid));
int sum=rem+quo;
if(sum==num)
{System.out.println("Kaprekar");}else{System.out.println("Not Kaprecar");}
}
}

Changing the type of Loop index i from int to long fixed the problem.
The square computation of i*i was overflowing the upper limit of int so by changing it to long we were able to get the required computation done.
Thanks to Rup for pointing this out.
The code which cleared all the test cases is here :-
import java.io.*;
import java.util.*;
public class Solution {
public static void main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
Scanner scan = new Scanner(System.in);
int p = scan.nextInt();
int q = scan.nextInt();
boolean exist = false;
if(q <= p){
System.out.println("INVALID RANGE");
return;
}
int m = 0,n = 0;
long sqr = 0;
String numb = "";
String[] digits = new String[2];
for(long i = p; i <= q; i++){
if(i == 1)System.out.print(1 + " ");
else{
sqr = i*i;
numb = String.valueOf(sqr);
if(numb.length() % 2 == 0){
digits[0] = numb.substring(0, numb.length()/2);
digits[1] = numb.substring(numb.length()/2);
}else{
digits[0] = numb.substring(0, (numb.length() - 1)/2);
digits[1] = numb.substring((numb.length() -1)/2);
}
if(digits[0] == "" )
m = 0;
if(digits[1] == "")
n = 0;
if(!digits[1].equals("") && !digits[0].equals("")){
m = Integer.parseInt(digits[0]);
n = Integer.parseInt(digits[1]);
}
if(i == (m + n) ){
System.out.print(i + " ");
exist = true;
}
}
}
if(exist == false){
System.out.println("INVALID RANGE");
}
}
}

import java.io.*;
import java.math.*;
import java.util.*;
class Kaprekar {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int p = scanner.nextInt();
int q = scanner.nextInt();
long i,n,s,a,c,k,d,e=0;
for(i=p;i<=q;i++)
{
k=i;d=0;
while(k!=0)
{
d++;
k=k/10;
}
c=0;s=0;n=i*i;
while(n!=0)
{
a=n%10;
n=n/10;
s=s+ (int)Math.pow(10,c)*a;
c++;
if(n+s==i&&(c==d||c==d-1)&&s!=0)
{
System.out.print(i+" ");
e++; break;
}
}
}
if(e==0)
{
System.out.println("INVALID RANGE");
}
scanner.close();
}
}

Binary to Decimal Java converter

I am creating a code that allows you to convert a binary number to a decimal number and vice versa. I have created a code that converts decimal to binary but can not workout how to implement the binary to decimal aspect.
My code for decimal to binary is below:
import java.util.*;
public class decimalToBinaryTest
{
public static void main (String [] args)
{
int n;
Scanner in = new Scanner(System.in);
System.out.println("Enter a positive interger");
n=in.nextInt();
if(n < 0)
{
System.out.println("Not a positive interger");
}
else
{
System.out.print("Convert to binary is: ");
binaryform(n);
}
}
private static Object binaryform(int number)
{
int remainder;
if(number <= 1)
{
System.out.print(number);
return " ";
}
remainder= number % 2;
binaryform(number >> 1);
System.out.print(remainder);
{
return " ";
}
}
}
An explanation to how the binary to decimal code work would help as well.
I have tried the method of the least significant digit*1 then the next least *1*2 then *1*2*2 but can not get it to work.
Thank you #korhner I used your number system with arrays and if statements.
This is my working code:
import java.util.*;
public class binaryToDecimalConvertor
{
public static void main (String [] args)
{
int [] positionNumsArr= {1,2,4,8,16,32,64,128};
int[] numberSplit = new int [8];
Scanner scanNum = new Scanner(System.in);
int count1=0;
int decimalValue=0;
System.out.println("Please enter a positive binary number.(Only 1s and 0s)");
int number = scanNum.nextInt();
while (number > 0)
{
numberSplit[count1]=( number % 10);
if(numberSplit[count1]!=1 && numberSplit[count1] !=0)
{
System.out.println("Was not made of only \"1\" or \"0\" The program will now restart");
main(null);
}
count1++;
number = number / 10;
}
for(int count2 = 0;count2<8;count2++)
{
if(numberSplit[count2]==1)
{
decimalValue=decimalValue+positionNumsArr[count2];
}
}
System.out.print(decimalValue);
}
}

sample:
00000100
0 - 1
0 - 2
1 - 4
0 - 8
0 - 16
0 - 32
0 - 64
0 - 128
Sum values with bit 1 = 4
Good luck!

int decimal = Integer.parseInt("101101101010111", 2);
or if you prefer to doit your self
double output=0;
for(int i=0;i<str.length();i++){
if(str.charAt(i)== '1')
output=output + Math.pow(2,str.length()-1-i);
}

Here is a program which does that.
Make sure the integers you give to int and not too large.
import java.util.Scanner;
public class DecimalBinaryProgram {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (true){
System.out.println("Enter integer in decimal form (or # to quit):");
String s1 = in.nextLine();
if ("#".equalsIgnoreCase(s1.trim())){
break;
}
System.out.println(decimalToBinary(s1));
System.out.println("Enter integer in binary form (or # to quit):");
String s2 = in.nextLine();
if ("#".equalsIgnoreCase(s2.trim())){
break;
}
System.out.println(binaryToDecimal(s2));
}
}
private static String decimalToBinary(String s){
int n = Integer.parseInt(s, 10);
StringBuilder sb = new StringBuilder();
if (n==0) return "0";
int d = 0;
while (n > 0){
d = n % 2;
n /= 2;
sb.append(d);
}
sb = sb.reverse();
return sb.toString();
}
private static String binaryToDecimal(String s){
int degree = 1;
int n = 0;
for (int k=s.length()-1; k>=0; k--){
n += degree * (s.charAt(k) - '0');
degree *= 2;
}
return n + "";
}
}
Of course for this method binaryToDecimal you can just do:
private static String binaryToDecimal(String s){
int n = Integer.parseInt(s, 2);
return n + "";
}
but I wanted to illustrate how you can do that explicitly.

do you want this?
private double dec(String s, int i) {
if (s.length() == 1) return s.equals("1") ? Math.pow(2, i) : 0;
else return (s.equals("1") ? Math.pow(2, i) : 0) + dec(s.substring(0, s.length() - 1), i - 1);
}
dec("101011101",0);

This is a version of a binary to decimal converter. I have used plenty of comments also. Just taught I would like to share it. Hope it is of some use to somebody.
import java.util.Scanner;
public class BinaryToDecimal
{
public static void main(String args[])
{
Scanner input = new Scanner(System.in);
System.out.println("Enter a binary number: ");
String binary = input.nextLine(); // store input from user
int[] powers = new int[16]; // contains powers of 2
int powersIndex = 0; // keep track of the index
int decimal = 0; // will contain decimals
boolean isCorrect = true; // flag if incorrect input
// populate the powers array with powers of 2
for(int i = 0; i < powers.length; i++)
powers[i] = (int) Math.pow(2, i);
for(int i = binary.length() - 1; i >= 0; i--)
{
// if 1 add to decimal to calculate
if(binary.charAt(i) == '1')
decimal = decimal + powers[powersIndex]; // calc the decimal
else if(binary.charAt(i) != '0' & binary.charAt(i) != '1')
{
isCorrect = false; // flag the wrong input
break; // break from loop due to wrong input
} // else if
// keeps track of which power we are on
powersIndex++; // counts from zero up to combat the loop counting down to zero
} // for
if(isCorrect) // print decimal output
System.out.println(binary + " converted to base 10 is: " + decimal);
else // print incorrect input message
System.out.println("Wrong input! It is binary... 0 and 1's like.....!");
} // main
} // BinaryToDecimal

I've written a converter that accepts both strings and ints.
public class Main {
public static void main(String[] args) {
int binInt = 10110111;
String binString = "10110111";
BinaryConverter convertedInt = new BinaryConverter(binInt);
BinaryConverter convertedString = new BinaryConverter(binString);
System.out.println("Binary as an int, to decimal: " + convertedInt.getDecimal());
System.out.println("Binary as a string, to decimal: " + convertedString.getDecimal());
}
}
public class BinaryConverter {
private final int base = 2;
private int binaryInt;
private String binaryString;
private int convertedBinaryInt;
public BinaryConverter(int b) {
binaryInt = b;
convertedBinaryInt = Integer.parseInt(Integer.toString(binaryInt), base);
}
public BinaryConverter(String s) {
binaryString = s;
convertedBinaryInt = Integer.parseInt(binaryString, base);
}
public int getDecimal() {
return convertedBinaryInt;
}
}

public static void main(String[] args)
{
System.out.print("Enter a binary number: ");
Scanner input = new Scanner(System.in);
long num = input.nextLong();
long reverseNum = 0;
int decimal = 0;
int i = 0;
while (num != 0)
{
reverseNum = reverseNum * 10;
reverseNum = num % 10;
decimal = (int) (reverseNum * Math.pow(2, i)) + decimal;
num = num / 10;
i++;
}
System.out.println(decimal);
}

Java: Error: Possible loss of precision

my program is almost ready to go I think, however, I can't seem to output the sum as a number like "3.2" or "5.2". For some reason, it's only returning the values as 2.0 or 3.0 or 4.0, like integers with a .0 at the end. Any help?
import java.io.Console;
import java.util.Scanner;
/**
*
* #author binka
*/
public class Samelson_Lincoln_Lab6 {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Scanner in = new Scanner(System. in );
System.out.println("Please enter a number?");
int number = in .nextInt();
double[] array = new double[number];
System.out.println();
int sign = 0;
double term = 0;
for (int i = 1; i < array.length; i++) {
if (sign == 0) {
term = Math.abs((4.0 / ((2.0 * i) - 1.0)));
array[i] = term;
sign = 1;
} else if (sign == 1) {
term = ((4.0) / ((2.0 * i) - 1));
array[i] = -term;
sign = 0;
}
System.out.println(array[i]);
}
boolean choice = true;
while (choice = true) {
System.out.println("Would you like to see the sum?: (Y or N)");
String choicesum = in .next();
choicesum.toUpperCase();
if ("Y".equals(choicesum)) {
double sum = computeSum(array);
System.out.println("Your sum is: " + sum);
choice = false;
break;
} else if ("N".equals(choicesum)) {
System.out.println("See ya!");
choice = false;
break;
} else {
System.out.println("Not a correct response, try again!");
}
}
}
public static int computeSum(double[] array) {
double sum = 0;
for (int i = 0; i < array.length; i++) {
sum = sum + array[i];
}
return sum;
}
}

while (choice = true) {
should at least be
while (choice == true) {
or even better
while (choice) {
To fix your actual error, change your method signature from
public static int computeSum(double[] array) {
to
public static double computeSum(double[] array) {