Thread: Java Array Program Help

Hi, I was wondering whether anyone could help me with this program?

Write a program that accepts two integer command-line arguments: x and k. THe program must construct an array of x random double values between -5..5. Then your program must repeat the following two steps k times:

1) Mutate the array
2)Display the array

To mutate the array, implement a routine

void mutate(double[] delta)

The method must accept a double array, pick a random element, and change it to a random double value -5..5.

You must print out all the arrays (it will be z x k number of arrays)

I'm not sure how to add the post tags but

I'm trying to figure out how to change the value of the array in the mutate function and then use that new value to replace the value in the main static void.
e.g. if x is 5 and it mutate the 3 array, I'm not sure how to replace the 3rd array in the main function with the mutated answer

import java.util.Arrays;
public class BeeMutate {
	public static int random;
	public static int n;
	public static int i;
 
	public static void main(String args[]) {
		n = Integer.parseInt(args[0]);
		int k = Integer.parseInt(args[1]);
		double mutated;
		double[] value = new double[n];
		for (int z = 0; z < k; z++) {
			for (int i = 0; i < value.length; i++) {
				value[i] = (Math.random() * 10 - 5);
 
			}
			mutated = mutate(value);
			value[random] = mutated;
			System.out.println(String.format("%.2f", Arrays.toString(value)));
			}
		}
 
	public static double mutate(double[] delta) {
		random = ((int) (Math.random() * n));
		delta[random] = (Math.random() * 10 - 5);
		return delta[random];
	}
}

--- Update ---

At the moment, it is obviously not going to be able to print out all the values[i] because the for loop closes. But I'm not sure how to run the for loop, assign a random value to each array box, then only mutate one, print them and run that entire function for the value of k

Essentially, how do I run the mutate program once in the for loop, even though n will run the loop mutiple times

for (int z = 0; z < k; z++) {
			for (int i = 0; i < value.length; i++) {
				value[i] = (Math.random() * 10 - 5);
					mutated = mutate(value);
			value[random] = mutated;
			System.out.println(String.format("%.2f", Arrays.toString(value)));
			}
			}
		}

--- Update ---

n and k are any positive integers that the user can enter. For the second loop (i), I'm confused as how to only run the mutate function once, as the loop will continue for each value up to n

for this case, lets say n = 5 and k = 10. The foor loop is used to assign a random variable to every array "box" that exists. So, to put a random number in value[0]....value[5]

there are two loops in order to run entire program multiple times. So since k is 10, the loop will complete 10 times and print out the 5 different arrays 10 times.

--- Update ---

for (int z = 0; z < k; z++) {
				for (int i = 0; i < value.length; i++) {
				value[i] = (Math.random() * 10 - 5);
				while (i != (n-1)) {
					continue;
				}
					mutated = mutate(value);
					value[random] = mutated;
					System.out.println(String.format("%.2f", Arrays.toString(value)));
				}
			}
		}

i thought that this would fix it, but now the program doesn't print anything.

Originally Posted by Norm

What does the program do when it executes? Does it ever end or is it in an infinite loop?
What is the purpose of the while loop?
It should show an error because the println statement is not correct.

Do you know about program comments? They are a very useful way to describe what a program is trying to do and how it is going to do it.
If the posted code had proper comments I would not have to ask questions like:
What is the purpose of the while loop?
What is the meaning of the contents of n and k?

How would i go around printing the entire array[i] in the loop? Thank you, I will try to add comments

Thank you so much! I think that I got it right!