Thread: Counting and Math.random

Hey, so I need some major help with this problem.. maybe not major, but I'm trying to generate random 100 numbers, from 0 to 9, in an array using Math.random, but it only outputs 0s which is very confusing to me. Also, I need to be able to count how many different integers there are like 0s, 1s, 2s... 8s, 9s. Also confused on how to do that exactly, thought I had it, but now I just confused my whole brain. Please help. Here's my code, I only got as far as the array then got stumped on the counting part. Thank you in advance!

import java.util.Arrays;
 
public class countDigits {
	public static void main(String[] args) {
 
		//Create random generator and values
		int numbers = (int)(Math.random() * 10);
		int arrayCount = 1;
		final int numOfArrays = 100;
		int[] digitArray = new int[numOfArrays];
		int counts = 0;
 
		//Create array
		for (arrayCount = 1; arrayCount <= digitArray.length; arrayCount++) {
			System.out.print(digitArray[numbers] + " | ");
		}
		//Count different integers
 
	}
}

and my results

0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0

how would I do that exactly with 100 different arrays? The programs I've seen only do something like

array[0] = 0
array[1] = 2
array[2] = 5
 
//etc.

Okay, so I put this in the array loop, not sure if it matters, but now the numbers change, so instead of 0 it would be 3 or 7, but they're all that same number.

for (arrayCount = 1; arrayCount <= digitArray.length; arrayCount++) {
			System.out.print(arrayCount + ": ");
			System.out.print((digitArray[arrayCount] = numbers) + " | ");
		}

But then it also says at the end.

94: 8 | 95: 8 | 96: 8 | 97: 8 | 98: 8 | 99: 8 | 100: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 100
	at countDigits.main(countDigits.java:20)

The numbers are just there to tell me how many there are.

I fix the index problem, but for the random numbers, I have to use the Math.random(); so I'm confused on getting that to work properly. because I have the

int numbers = (int)(Math.random() * 10);
&&
System.out.print((digitArray[arrayCount] = numbers) + " | ");

so I don't see exactly what I could be doing wrong because technically I'm assigning values to every element by using the second code right?

Oh, I figured out what you were saying now. Thanks! But now, I'm confused about the counting each integer from that one array.. Some people say to make an array of 10 (0-9) integers then count them that way or to do something way different that confuses me as well.. :/

Sorry, I don't think I'm understanding well enough. Although I tried to increment each element, it's just the same number for all of them which is what happened before. This was my code

digitArray[0] = counts++;
			digitArray[1] = counts++;
			digitArray[2] = counts++;
			digitArray[3] = counts++;
			digitArray[4] = counts++;
			digitArray[5] = counts++;
			digitArray[6] = counts++;
			digitArray[7] = counts++;
			digitArray[8] = counts++;
			digitArray[9] = counts++;

Okay, so I have no idea what you mean by that to be honest. This is what I have written down.

for (arrayCount = 1; arrayCount < digitArray.length; arrayCount++) {
			System.out.print(arrayCount + ": ");
			System.out.print((digitArray[arrayCount] = (int)(Math.random() * 10)) + " | ");
		}
		//Count different integers - new array
int[] countVarArray = new int[11];
		int countVar = 0;
 
		for (countVarArray[10]++; arrayCount < digitArray.length; countVar++) {
			System.out.println();
		}
 
 
			System.out.println("\n" + countVar);
	}

with this as a result

1: 5 | 2: 2 | 3: 6 | 4: 2 | 5: 0 | .... | 95: 9 | 96: 9 | 97: 7 | 98: 2 | 99: 9 | 100: 3 |
0

with the 0 being the count of each integer.. So, I put what you said pretty much, or tried to.

So, do you mean to put another loop inside of the first loop? or put it all in one loop? Sorry I don't really get this.. This is what I put.

int[] digitArray = new int[101];
		int[] counts = new int[10];
 
		//Generate 100 random numbers
		for (int arrayCount = 0; arrayCount < digitArray.length; arrayCount++) {
			int randNum = (int)(Math.random() * 10);
			System.out.print((digitArray[arrayCount] = randNum) + " ");
		//count
			for (randNum = 0; randNum < counts.length; randNum++) {
				System.out.print(randNum);
			}
		}

The assignment asks that for the program to count the number of times each distinct numbers occurs. So, it wants to show how many 0s, how many 1s, etc.

Yep, not sure if this is totally what you meant, but this is what I got from it. I tried to print it by putting System.out.println(counts); but that only gave me '[I@1b845568' and I have no idea what that code is. This is what I have so far.

	int[] digitArray = new int[101];
		int[] counts = new int[10];
		int arrayCount = 0;
 
		//Generate 100 random numbers
		for (arrayCount = 1; arrayCount < digitArray.length; arrayCount++) {
			int randNum = (int)(Math.random() * 10);
			System.out.print(arrayCount + ": ");
			System.out.print((digitArray[arrayCount] = randNum) + " | ");
		}
		//count
		while (arrayCount < digitArray.length) {
				counts[0]++;
				counts[1]++;
				counts[2]++;
				counts[3]++;
				counts[4]++;
				counts[5]++;
				counts[6]++;
				counts[7]++;
				counts[8]++;
				counts[9]++;
		}
		System.out.println(counts[0]);

//array
int[] counts = new int[10];
 
	//random number loop
		for(int r = 0; r < 20; r++) {
			int randNum = (int)(Math.random() * 10);
			System.out.print(randNum + " ");
		}

output:

8 8 4 3 1 8 4 4 3 2 1 8 9 8 6 3 0 8 1 3

//array
int[] counts = new int[10];
 
	//random number loop
		for(int r = 0; r < 20; r++) {
			int randNum = (int)(Math.random() * 10);
			System.out.print(randNum + " ");
                        counts[0]++;
		}

output:

8 8 4 3 1 8 4 4 3 2 1 8 9 8 6 3 0 8 1 3

So like this? Since I can't control what numbers show up?

//array
int[] counts = new int[10];
 
	//random number loop
		for(int r = 0; r < 20; r++) {
			int randNum = (int)(Math.random() * 10);
			System.out.print(randNum + " ");
                        counts[randNum]++;
		}