Develop Reference

How can I make the script that counts which number occurred most often and counts how many times do each of the 10 random numbers occur

To explain about the program that I am making, it is program that asks the user how many times he would like his coin to flip. In this program, the coin of the head is even, and the odd is the tail.
I created a script that randomizes numbers from 1 to 10 based on the number you entered. And also I've made the script that how many odd and even numbers had come out, but I don't know how to make a script that shows how many times do each of the 10 random numbers occur and which number occurred most often.
Here is the script that I have made:
import java.util.*;
public class GreatCoinFlipping {
public static void main(String[] args) {
System.out.println("How many times do you want to flip the coin? : ");
Scanner sc = new Scanner(System.in);
int amount = sc.nextInt();
int[] arrNum = new int[amount];
int even = 0, odd = 0;
for (int i = 0; i < amount ; i++) {
arrNum[i] = (int)(Math.random() * 10 + 1);
System.out.println(arrNum[i]);
if (arrNum[i] % 2 == 0) even++;
else odd++;
}//end for
System.out.println("Head: " + even + ", Tail: " + odd);
}//end main
}//end class
What I am expecting on this script that that I want to make the script that shows how many times do each of the 10 random numbers occur and which number occurred most often and I want to make it by the count method. But the ramdon number part has to be in array method. Can someone please help me with this problem?

The arrNum variable will contain an array of all occurences of each number. So if you want to count, for example, how many times 4 occurred in this, you can do this:
Arrays.stream(arrNum).filter(n -> n == 4).count()
For 7 you can do this:
Arrays.stream(arrNum).filter(n -> n == 7).count()
And you can do the same for other digits (1 to 10).
This would be a simple/straight-forward way of doing it. You can also improve it by creating a method that returns this count:
public static int getCount(int[] arr, int num) {
return Arrays.stream(arr).filter(n -> n == num).count();
}
And then call this in a loop:
for(int i=1; i<=10; i++) {
System.out.println("Count for " + i + ": " + getCount(arrNum, i));
}

To keep track of the random number you generate you can use a array. The array starts out as all 0's and is of size 10 (because there are 10 numbers between 0-9).
int size = 10;
int numbers_counter[] = new int[size];
// initialize the values
for(int i = 0; i < size; i++){
numbers_counter[i] = 0;
}
// count some random numbers
for(int i = 0; i < 100; i++){
numbers_counter[(int)(Math.random() * size)] += 1;
}
// print how many times each number accured
for(int i = 0; i < size; i++){
System.out.println("" + i + " occured: " + numbers_counter[i] + " times");
}
You can apply this method to your code.

how do i get rid of the zero that shows up after all my elements in my array are listed?

i have to make a program that prints out the elements of an array filled with random numbers backwards but it also prints out a zero after my variables? i think it has something to do with my for-loops but i get a java.lang.ArrayIndexOutOfBoundsExceptionerror any time i try to change them.
edit: i also noticed that the first printed element is always zero. i don't really see it as a problem but what could be causing that?
import java.util.*;
public class EZD_printBackwards
{
static int vars[] = new int[10];
static int backwards()
{
Random rand = new Random();
int bkwds = vars[0];
for (int a = 0; a < 10; a++)
{
vars[a] = rand.nextInt(100)+1;
}
for (int x = 10; x > 0; x--)
{
System.out.println("Element " + x + " is " + vars[x] );
}
return bkwds;
}
public static void main(String Args[])
{
int option;
Scanner kbReader = new Scanner(System.in);
do
{
System.out.println(backwards());
System.out.print("Type 1 to run again. Type 0 to end the program.");
option = kbReader.nextInt();
while(option !=1 && option !=0)
{
if (option != 1 && option != 0)
{
System.out.print("Please enter 1 to run again or 0 to end the program.");
option = kbReader.nextInt();
}
}
}while(option==1);
System.out.println("");
}
}

In your example, vars is size 10. The second for loop starts at index x = 10 which is greater than the last index of vars because array index starts at zero. To fix the issue, you should use this condition in your for loop:
for (int x = vars.length -1; x >= 0; x--)
{
System.out.println("Element " + x + " is " + vars[x] );
}

You have two problems:
FIRST => For loop out of bounds
you want to go through 10 elements, therefore your
for (int x = 10; x > 0; x--)
should be
for (int x = 9; x >= 0; x--)
0..9 is 10 elements and the same things goes for
for (int a = 0; a < 10; a++)
to
for (int a = 0; a < 9; a++)
SECOND ==> 0 at the end
That's because you do
System.out.println(backwards());
instead of
backwards();

you are returning the value of "bkwds", and you are initializing "bkwds" with vars[0] , and i guess in java the compiler initialize all the values of an array with 0 ,
in other words your probleme is in System.out.println(backwards());
remove it with
backwards();
and it should work !
EDIT
your look is out of bound either replace it with this
for (int a = 0; a < 10; a++)
or
do this
for (int a = 9; a > 0; a--)

The range of your Array is from 0 up to and including 9. Your for loop, however, is starting from 10 and coming down to index 1. It should start from 9 and comes down to index zero. This, however, does not explain printing random 0! The reason for these zeros is you have an int bkwds which youb set to vars[0] at the beginning of your function. But, since it is not initialized, it will be set to 0 (the default for int) In your main, you call the function in a print statement, which I suppose keeps printing that falsely, useless initialized variable that you return :)

As arrays are indexed from zero, change to
System.out.println("Element " + x + " is " + vars[x-1] );
output
Element 10 is 31
Element 9 is 63
Element 8 is 82
Element 7 is 46
Element 6 is 67
Element 5 is 24
Element 4 is 3
Element 3 is 27
Element 2 is 37
Element 1 is 13
edit
And change this
System.out.println(backwards());
to
backwards();
As the return value of this method is useless and not used, change this method to return void

Negative Arrays and Error Messages

//MY TASK IS TWO MERGE TO ARRAYS INTO ASCENDING ORDER.Your program will accept each array as input from the keyboard. You do not know ahead of time how many values will be entered, but you can assume each array will have a maximum length of 10,000 elements. To stop entering values enter zero or a negative number. You should disregard any non-positive numbers input and not store these in the array.
The elements of the two input arrays should be in increasing order. In other words, each array element must have a value that is greater than or equal to the previous element value. An array may contain repeated elements.
import java.util.Scanner;
import java.lang.Math;
class Main {
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
int one[]= new int[10000];
int two[]= new int[10000];
int lengthShort=0;
int lengthLong=0;
int a =0;
int b =0;
System.out.println("Enter the values for the first array, "
+ "up to 10000 values, enter a negative number to quit");
for(int i=0; i<one.length && scan.hasNext(); i++){
one[i] = scan.nextInt();
a++;
if(one[i]<0){
one[i]=0;
break;
}
}
int length1 = a-1;
System.out.println("Enter the values for the second array, "
+ "up to 10000 values, enter a negative number to quit");
for(int i=0; i<two.length && scan.hasNext(); i++){
two[i] = scan.nextInt();
b++;
if(two[i]<0){
two[i]=0;
break;
}
}
int lengthTwo = b-1;
int mergeOne[] = new int[length1];
for (int i = 0; i<mergeOne.length; i++){
mergeOne[i]=one[i];
}
int mergeTwo[] = new int[lengthTwo];
for (int i = 0; i<mergeTwo.length; i++){
mergeTwo[i]=two[i];
}
System.out.println("First Array:");
for(int i=0; i<mergeOne.length; i++){
System.out.print(mergeOne[i] + " ");
}
System.out.println("\nSecond Array:");
for(int i=0; i<mergeTwo.length; i++){
System.out.print(mergeTwo[i] + " ");
}
if(mergeOne.length<=mergeTwo.length){
lengthLong = mergeTwo.length;
lengthShort = mergeOne.length;
}
else if(mergeOne.length>=mergeTwo.length){
lengthShort = mergeTwo.length;
lengthLong = mergeOne.length;
}
int merged[] = new int[length1 + lengthTwo];
for(int i = 0; i<lengthShort; i++){
if(i==0){
if(mergeOne[i]<=mergeTwo[i]){
merged[i] = mergeOne[i];
merged[i+1] = mergeTwo[i];
}
else if(mergeTwo[i]<=mergeOne[i]){
merged[i] = mergeTwo[i];
merged[i+1]= mergeOne[i];
}
}
else if(i>0){
if(mergeOne[i]<=mergeTwo[i]){
merged[i+i] = mergeOne[i];
merged[i+i+1] = mergeTwo[i];
}
else if(mergeTwo[i]<=mergeOne[i]){
merged[i+i] = mergeTwo[i];
merged[i+i+1]= mergeOne[i];
}
}
}
if(mergeOne.length<mergeTwo.length){
for(int k=lengthShort; k<lengthLong; k++){
merged[k]=mergeTwo[k];
}
}
if(mergeOne.length>mergeTwo.length){
for(int k=lengthShort; k<lengthLong; k++){
merged[k]=mergeOne[k];
}
}
for(int i = 0; i<merged.length; i++){
if((i+1)==merged.length)
break;
if(merged[i]>merged[i+1]){
int temp = merged[i+1];
merged[i+1]=merged[i];
merged[i]= temp;
}
}
System.out.println("\nMerged array in order is: ");
for(int i = 0; i<merged.length; i++){
System.out.print(merged[i] + " ");
}
}
}
//My code compiles in drjava but I have two issues:
1) It doesn't order the numbers in ascending order
2) When I run it through the site I have to submit this on it gives me the message as follows:
Runtime Error
Exception in thread "main" java.lang.NegativeArraySizeException
at Main.main(Main.java:281)
at Ideone.assertRegex(Main.java:94)
at Ideone.test(Main.java:42)
at Ideone.main(Main.java:29)

You'll need to rethink your merge algorithm. Suppose you input arrays are
1 5 10 50 100 500
2 4 6 8 10 12 14 16
You'll need to repeatedly decide which element is smaller to put into the output. So after selecting N elements, your output will look like
1 2 4 5 6 8 10 10 12 14
And you will need to have indexes pointing at the place in the input arrays you'll need to look at next:
1 5 10 50 100 500
^^
2 4 6 8 10 12 14 16
^^
As you can see, the indexes could be at very different places in the input arrays. However, your code does a lot of this:
if(mergeOne[i]<=mergeTwo[i]){
which means it's only comparing elements from the input that are in the same location. This doesn't work, and trying to swap elements in the output after the fact isn't good enough to get the job done.
Basically, instead of having one index and comparing the elements of the two input arrays at the same index, you'll need two indexes. I'll let you take it from there, but I think you can figure it out.
(And I have no idea why you're getting NegativeArraySizeException.)

Loop Counting in Java

What I have is a program that prints out 4000+ random digits in the range of 1 to 99999. After printing, it shows the range, and a couple of other things, and then asks user for 5 numbers to be input and tells how many times it had to run the loop, but I'm getting an exception in main upon print, it's coming from the main for loop. Screenshot is attached. Desired should look something like:
(Randomly generated numbers):
25
192
33
(User Enters) Please enter number: 33
(System Response) It took 3 times to find the number.
If the number is not listed, as it is over 4000 integers, it will say, not found.
Here is code and screenshot:
Screenshot
Exception in Main java.lang.ArrayIndexOutOfBoundsException:0
Thank You!
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int[] input = new int[0];
int[] arrayone = new int[4096];
int loop = 0;
for(int i = 0; i < arrayone.length; i++) {
arrayone[i] = (int)(Math.random() * 99999 + 1);
for(int in = 0; in<input.length; in++) {
if (arrayone[i] == input[in]) {
loop++;
}
}
}
for (int i = 0; i < 5; i++) {
System.out.println("Please enter a number between " + min + " and " + max);
input[0] = s.nextInt();
if (min <= input[0] && input[0] <= max) {
System.out.println("It took " + loop + " time(s) to find the number " + input);
}
}
}

The problem with your input array is that you initialize it with a size of 0, so when you try to access the first location [0], you run out of the bounds since your array has a size of 0. In your answer you were also trying to determine the loops before asking the question. While doing this you were also trying go past the bounds of your input array with a size 0. What you should do is initialize your array of numbers first then for each guess loop through and determine if it's within the bounds of your max and min. Also note that just because the numbers are within the max and min doesn't guarantee the number is contained in the array because the numbers are not going to be sequential from max to min. You should check where you end up after your for-loop check for the input.
public static void main(String random[])
{
Scanner s = new Scanner(System.in);
int input = new int[5];
int[] arrayone = new int[4096];
int loop = 0;
//don't do anything here except fill the array with values
for(int i = 0; i < arrayone.length; i++) {
arrayone[i] = (int)(Math.random() * 99999 + 1);
}
//ask the user for 5 inputs
for (int index = 0; index < input.length; index++) {
System.out.println("Please enter a number between " + min + " and " + max);
input[index] = s.nextInt();
//check to see if the number is valid
if (min <= input[index] && input[index] <= max) {
//loop through the arrayone to determine where it is
for(int i = 0; i < arrayone.length; i++) {
//if it is not in the current index at i increment the loop count
if (arrayone[i] != input[index]) {
loop++;
}
//we have found where it is and should break out of the loop
else {
break;
}
}
//check if we found it based on how much we incremented
if(i != arrayone.length)
{
//output how long it took to find the number
System.out.println("It took " + loop + " time(s) to find the number " + input[index]);
}
else
{
System.out.println(input[index] + " not found!");
}
//now reinitialize the loop to 0 for the next guess
loop = 0;
}
}
//always remember to close your scanners
s.close();
}
}

int[] input = new int[0];
This creates an array with size of 0, so when you try save value it throws an exception because you are exceeding array size.
Solution: set valid size of array or use list.
The ArrayList is (simplifying) resizeable version of array. Use it like this:
List<Integer> input = new ArrayList<>();
input.add(5); //Adds 5 to list
input.get(0); //Read object of index 0
for(int value : list) { //Loop: for each element in list ...
System.out.println(value);
}
//Checks whether list contains 5
System.out.println(list.contains(5));
Also, do you actually need input to be an array? Because right now it looks like you don't need it at all.

Finding how many times an item Appears in an Array

Given an array of integers ranging from 1 to 60, i'm attempting to find how many times the numbers 1-44 appear in the array. Here is my method
public static void mostPopular(int[] list, int count)
{
int[] numbers;
numbers = new int[44];
for (int i = 0; i<count;i++)
{
if (list[i]<45 )
{
numbers[i-1]=numbers[i-1]+1; //error here
}
}
for (int k=0; k<44;k++)
{
System.out.println("Number " + k + " occurs " + numbers[k-1]+ "times");
}
}
I'm trying to iterate through the array, list, that contains over 5000 numbers that are between 1-60, then test if that number is less than 45 making it a number of interest to me, then if the integer is 7 for example it would increment numbers[6] By 1. list is the array of numbers and count is how many total numbers there are in the array. I keep getting an ArrayIndexOutOfBoundsException. How do I go about fixing this?

Replace this line numbers[i-1]=numbers[i-1]+1;
with numbers[list[i] - 1] = numbers[list[i] - 1] + 1;
Now it will update the count of correct element.

You need to increment numbers[list[i]] because that's your value which is smaller than 45. i goes up to 5000 and your array numbers is too small.
You should really start using a debugger. All the modern IDE have support for it (Eclipse, IntelliJ, Netbeans, etc.). With the debugger you would have realized the mistake very quickly.

If your initial value is less than 45, it will add 1 to numbers[i-1]. However, since you start with i=0, it will try to add 1 to the value located at numbers[-1], which doesn't exist by law of arrays. Change i to start at 1 and you should be okay.

Very close, but a few indexing errors, remember 0-1 = -1, which isn't an available index. Also, this isn't c, so you can call list.length to get the size of the list.
Try this (you can ignore the stuff outside of the mostPopular method):
class Tester{
public static void main(String args[]){
int[] list = new int[1000];
Random random = new Random();
for(int i=0; i<list.length; i++){
list[i] = random.nextInt(60) + 1;
}
mostPopular(list);
}
public static void mostPopular(int[] list)
{
int[] numbers = new int[44];
for (int i = 0; i< list.length ;i++)
{
int currentInt = list[i];
if(currentInt<45 )
{
numbers[currentInt - 1] = (numbers[currentInt -1] + 1);
}
}
for (int k=0; k<numbers.length; k++)
{
System.out.println("Number " + (k+1) + " occurs " + numbers[k]+ "times");
}
}
}

When i is 0, i-1 is -1 -- an invalid index. I think that you want the value from list to be index into numbers. Additionally, valid indices run from 0 through 43 for an array of length 44. Try an array of length 45, so you have valid indices 0 through 44.
numbers = new int[45];
and
if (list[i] < 45)
{
// Use the value of `list` as an index into `numbers`.
numbers[list[i]] = numbers[list[i]] + 1;
}

numbers[i-1]=numbers[i-1]+1; //error here
change to
numbers[list[i]-1] += 1;
as list[i]-1 because your number[0] store the frequency of 1 and so on.
we increase the corresponding array element with index equal to the list value minus 1
public static void mostPopular(int[] list, int count)
{
int[] numbers = new int[44];
for (int i = 0; i<count;i++)
{
//in case your list value has value less than 1
if ( (list[i]<45) && (list[i]>0) )
{
//resolve error
numbers[list[i]-1] += 1;
}
}
//k should start from 1 but not 0 because we don't have index of -1
//k < 44 change to k <= 44 because now our index is 0 to 43 with [k-1]
for (int k=1; k <= 44;k++)
{
System.out.println("Number " + k + " occurs " + numbers[k-1]+ "times");
}
}