Fill an array with random numbers

Question

I need to create an array using a constructor, add a method to print the array as a sequence and a method to fill the array with random numbers of the type double.

He

Answer 1

You can simply solve it with a for-loop

private static double[] anArray;

public static void main(String args[]) {
    anArray = new double[10]; // create the Array with 10 slots
    Random rand = new Random(); // create a local variable for Random
    for (int i = 0; i < 10; i++) // create a loop that executes 10 times
    {
        anArray[i] = rand.nextInt(); // each execution through the loop
                                        // generates a new random number and
                                        // stores it in the array at the
                                        // position i of the for-loop
    }
    printArray(); // print the result
}

private static void printArray() {
    for (int i = 0; i < 10; i++) {
        System.out.println(anArray[i]);
    }
}

Next time, please use the search of this site, because this is a very common question on this site, and you can find a lot of solutions on google as well.

Answer 2

I tried to make this as simple as possible in Java. This makes an integer array of 100 variables and fill it with integers between 0 and 10 using only three lines of code. You can easily change the bounds of the random number too!

int RandNumbers[]=new int[100];
for (int i=0;i<RandNumbers.length;i++)
    RandNumbers[i]=ThreadLocalRandom.current().nextInt(0,10);

Answer 3

Probably the cleanest way to do it in Java 8:

private int[] randomIntArray() {
   Random rand = new Random();
   return IntStream.range(0, 23).map(i -> rand.nextInt()).toArray();
}

Answer 4

You can call the randomFill() method in a loop and fill your array in the main() method like this.

public static void main(String args[]) {
    for (int i = 0; i < anArray.length; i++) {
        anArray[i] = randomFill();
    }
}

You would then need to use rand.nextDouble() in your randomFill() method the array to be filled is a double array. The below snippet should help you get random double values to be filled into your array.

double randomDoubleValue = rand.nextDouble();
return randomDoubleValue;

Answer 5

Try this:

public void double randomFill() {
    Random rand = new Random();
    for (int i = 0; i < this.anArray.length(); i++)
        this.anArray[i] = rand.nextInt();
}

Answer 6

If the randomness is controlled like this there can always generate any number of data points of a given range. If the random method in java is only used, we cannot guarantee that all the numbers will be unique.

package edu.iu.common;

import java.util.ArrayList;
import java.util.Random;

public class RandomCentroidLocator {

public static void main(String [] args){
	
	int min =0;
	int max = 10;
	int numCentroids = 10;
	ArrayList<Integer> values = randomCentroids(min, max, numCentroids);	
	for(Integer i : values){
		System.out.print(i+" ");
	}
	
}

private static boolean unique(ArrayList<Integer> arr, int num, int numCentroids) {

	boolean status = true;
	int count=0;
	for(Integer i : arr){
		if(i==num){
			count++;
		}
	}
	if(count==1){
		status = true;
	}else if(count>1){
		status =false;
	}
	

	return status;
}

// generate random centroid Ids -> these Ids can be used to retrieve data
// from the data Points generated
// simply we are picking up random items from the data points
// in this case all the random numbers are unique
// it provides the necessary number of unique and random centroids
private static ArrayList<Integer> randomCentroids(int min, int max, int numCentroids) {

	Random random = new Random();
	ArrayList<Integer> values = new ArrayList<Integer>();
	int num = -1;
	int count = 0;
	do {
		num = random.nextInt(max - min + 1) + min;
		values.add(num);
		int index =values.size()-1;
		if(unique(values, num, numCentroids)){				
			count++;
		}else{
			values.remove(index);
		}
		
	} while (!( count == numCentroids));

	return values;

}

}