25个随机数偶数和奇数发生器

Question

I need to generate 25 random numbers and then separate them into two arrays, depending on whether they are odd or even. This is my expected output:

Even: 40 10 70 58 20 18 74 44 14 54 50 42
Odd: 21 75 29 69 7 41 33 35 21 13 93 73 33

This is what I have so far:

public static void main(String[] args) {   
Scanner input = new Scanner(System.in).useDelimiter("\n");
int[] randomNumbers = new int[25];
int[] evenNumbers = new int[25];
int[] oddNumbers = new int[25];
int k = 0, l = 0;

for (int i= 0; i< randomNumbers.length; i++) {
    randomNumbers[i] = (int) (Math.random() * 99);
}
for (int i = 0; i < 25; i++) {
    if (randomNumbers[i] % 2 == 0) {
        evenNumbers[k] = randomNumbers[i];
        k++;
    } else {
        oddNumbers[l] = randomNumbers[i];
        l++;
    }
}System.out.print("Even: ");
for (int i = 0; i< evenNumbers.length; i++) {
    System.out.print(evenNumbers[i] + " ");

}System.out.println("");
System.out.print("Odd: ");
for (int i= 0; i < oddNumbers.length; i++) {
    System.out.print(oddNumbers[i] + " ");
    }
  }
}

Here is my actual output:

Even: 40 10 70 58 20 18 74 44 14 54 50 42 0 0 0 0 0 0 0 0 0 0 0 0 0
Odd: 21 75 29 69 7 41 33 35 21 13 93 73 33 0 0 0 0 0 0 0 0 0 0 0 0

I would like to know how to get rid of the zeros at the end of each output.

Answer 1

int[] evenNumbers = new int[25]; will create an array of 25 ints that are initialized to 0.

The loop will then print all 25 of those ints, even if they haven't been replaced:

for (int i = 0; i< evenNumbers.length; i++) {
  System.out.print(evenNumbers[i] + " ");
}

To fix that either loop from 0 to k-1 (eg i < k ) or use List<Integer> instead of an int array.

The same applies to the odd numbers, you'd just use i < l instead.

Answer 2

When an int array is initiated, it is filled with 0s as the initial value. You have 2 options.

Option 1:

import java.util.ArrayList;

And use an ArrayList to store the latter even and odd integers. This is not an optimal solution as you are looking for a small amount of numbers.

Option 2:

Stop calling the System.out.println(); function when a 0 is reached. 0 is considered an even number, so you need to start printing the odd numbers, count how many there are and stop at a 0 and then start printing the remaining even numbers. Code:

int count = 0;
System.out.print("Odd: ");
for (int i= 0; i < oddNumbers.length; i++) {
    if (oddNumbers[i]!=0) {
        System.out.print(oddNumbers[i] + " ");
        count++;
    }
}
System.out.print(System.lineSeparator()+"Even: ");//Uses the system-specific new-line character which is extracted with System.lineSeparator().
for (int i = 0; i< evenNumbers.length; i++) {
    count++;
    if (count==26) {
        break;
    }
    System.out.print(evenNumbers[i] + " ");
}

Answer 3

The zeros are printed because you have created an array of 25 ints . Each of these 25 ints are initialized to zeros(the default value for primitive int in java).

To achieve your goal you have two options:

1. You can use an ArrayList<Integer> instead of an array. ArrayList is just a resizing array internally.. OR
2. You have to include two counters that keep track of how many elements you have inserted in both the odd/even arrays.

Answer 4

package test2;

import java.util.Scanner;

public class StackO1 {

    public static void main(String[] args) {   
        Scanner input = new Scanner(System.in).useDelimiter("\n");
        int[] randomNumbers = new int[25];
        int[] evenNumbers = new int[25];
        int[] oddNumbers = new int[25];
        int k = 0, l = 0;

        for (int i= 0; i< randomNumbers.length; i++) {
            randomNumbers[i] = (int) (Math.random() * 99);
        }
        for (int i = 0; i < 25; i++) {
            if (randomNumbers[i] % 2 == 0) {
                evenNumbers[k] = randomNumbers[i];
                k++;
            } else {
                oddNumbers[l] = randomNumbers[i];
                l++;
            }
        }System.out.print("Even: ");
        for (int i = 0; i< k; i++) {
            System.out.print(evenNumbers[i] + " ");

        }System.out.println("");
        System.out.print("Odd: ");
        for (int i= 0; i < l; i++) {
            System.out.print(oddNumbers[i] + " ");
            }
          }
        }

Answer 5

I would suggest you a different approach :)
1) You don't need two for loops - one to generate random numbers and the second to separate them in odd and even. You can do this with one the for-loop.
2) Use List<Integer> instead array. Use array only if it is requered by the task.
3) Perhaps, you don't need randomNumbers variable.
4) If you use 0 as special value be careful. It is possible to get zero value from Math.random() Math.random() and zero value.

So this is the code

public static void main(String[] args) {
    int NUM_OF_NUMS = 25;

    List<Integer> randomNumbers = new ArrayList<>();
    List<Integer> evenNumbers = new ArrayList<>();
    List<Integer> oddNumbers = new ArrayList<>();

    for (int i = 0; i < NUM_OF_NUMS; i++) {
        int randomNumber = (int) (Math.random() * 99);
        randomNumbers.add(randomNumber);

        if (randomNumber % 2 == 0) {
            evenNumbers.add(randomNumber);
        } else {
            oddNumbers.add(randomNumber);
        }
    }

    printArrays(evenNumbers, oddNumbers);
}

private static void printArrays(List<Integer> evenNumbers, List<Integer> oddNumbers) {
    System.out.print("Even: ");
    for (int num : evenNumbers) {
        System.out.print(num + " ");
    }
    System.out.println("");

    System.out.print("Odd : ");
    for (int num : oddNumbers) {
        System.out.print(num + " ");
    }
}