使用数组随机组合字符串

Question

I'm trying to figure out how to combine 2 random Strings entered by the user. This program is kind of like a Mad Libs game but instead it is for creating a poem. I first start by asking the user to enter the number of nouns to use, and then storing them into an array, and follow by asking the amount of adjectives, which also are stored in an array.

Precisely what is asked is as follows:

Generate your poem by choosing at random combinations of noun and adjectives. You are not allowed to pick a noun or an adjective again until you have used all sets of noun and adjectives that the user has provided, respectively.

Now I am asked to generate a poem by combining the entered nouns and adjectives, but the generator needs to be random. How would I do this? So far my program is as follows:

import java.util.Scanner;
public class A3Question1 
{

public static void main(String[] args) 
{
    Scanner keyboard = new Scanner(System.in);
    boolean loop1 = false;
    boolean loop2 = false;
    boolean loop3 = false;
    int numNouns = 0, numAdjectives = 0;
    String[] nouns = new String[numNouns];
    String[] adjectives = new String[numAdjectives];

    System.out.println("-----------------------------------------");
    System.out.println("           Let's write a poem!           ");
    System.out.println("-----------------------------------------");
    System.out.println();

    while (!loop1)
    {
        System.out.print("How many nouns? (min 3): ");
        numNouns = keyboard.nextInt();

        if (numNouns < 3)
        {
            continue;
        }
        else
        {
            loop1 = true;
        }

        System.out.println("Enter " + numNouns + " nouns: ");
        nouns = new String[numNouns];

        for (int i = 0; i < numNouns; i++)
        {
            nouns[i] = keyboard.next();
        }
    }
    while (!loop2)
    {
        System.out.print("How many adjectives? (min 3): ");
        numAdjectives = keyboard.nextInt();

        if (numAdjectives < 3)
        {
            continue;
        }
        else
        {
            loop2 = true;
        }

        System.out.println("Enter " + numAdjectives + " adjectives: ");
        adjectives = new String[numAdjectives];

        for (int j = 0; j < numAdjectives; j++)
        {
            adjectives[j] = keyboard.next();
        }

        while (!loop3)
        {
            System.out.println("\n-----------------------------------");
            System.out.println("        Here is my Java Poem!         ");
            System.out.println("           **LOOK AROUND**            ");
            System.out.println("-----------------------------------");
            System.out.println();

            for (int i = 0; i < numNouns && i < numAdjectives; i++)
            {                   
                int num1 = (int) (Math.random() * numNouns); 
                int num2 = (int) (Math.random() * numAdjectives);
                System.out.println(nouns[num1] + adjectives[num2]);
            }

            System.out.println("\nAnother poem? (y/n): ");
            String again = keyboard.next();

            if (again.charAt(0) == 121 || again.charAt(0) == 89)
            {
                continue;
            }
            else
            {
                loop3 = true;
            }
        }

        System.out.println("Thank you for using POEM GENERATOR! Have a good day!");         
    }       
    keyboard.close();
}

}

Sample output:

https://postimg.org/image/6ogwggw9f/

Edit**: I cleaned up the code and combined the arrays randomly together. However, the random arrays generated cannot be reused again and I'm trying to figure out how to avoid this problem. I also need to indent the poem properly as seen in the picture. For example, the first output has no space, second output has a tab, and third has two tabs.

Answer 1

Use a Random object to select a random index in your arrays. A second random could select a whether the noun or adjective array should be picked from.

public String randomPoem(String[] nouns, String[] adjectives) {
    Random random = new Random();
    ArrayList<String> nounList = new ArrayList<>(Arrays.asList(nouns));
    ArrayList<String> adjList = new ArrayList<>(Arrays.asList(adjectives));
    String value = "";
    if (random.nextBoolean()) {
        int index = random.nextInt(nounList.size());
        value += nounList.remove(index);
    } else {
        int index = random.nextInt(adjList.size());
        value +=  adjList.remove(index);
    }
    return value;
}

Answer 2

You have to randomize the arrays in place. A simple method to do that is to pick any 2 elements in the array and swap them with each other. Do that enough times and you will have a randomized array.

Here's a sample

package com.example;

import java.util.Random;

public class RandomTest {
    public static void main(String[] args) {
        String[] nouns = {"roses", "tulips", "grass"};
        shuffle(nouns, 50);
        String[] adjectives = {"red", "lovely", "gorgeous", "green"};
        shuffle(adjectives, 50);

        for(int i = 0; i < nouns.length && i < adjectives.length; i++) {
            System.out.println(adjectives[i] + " " + nouns[i]);
        }
    }

    public static void shuffle(String[] list, int swapCount) {
        Random random = new Random();
        for(int i = 0; i < swapCount; i++) {
            int index1 = random.nextInt(list.length);
            int index2 = random.nextInt(list.length);

            //Swap these two with each other
            String temp = list[index1];
            list[index1] = list[index2];
            list[index2] = temp;
        }
    }
}

Output in successive runs

lovely tulips
gorgeous roses
red grass

lovely grass
gorgeous tulips
green roses

lovely tulips
red roses
green grass