Bluecoding test

Test1.java

import java.util.*;

class Test1 {

    public static void main(String[] args) {

        System.out.println(test1(new int[] {1,2,4,5,6,8,2,5,3,2}));

        test2();

        System.out.println(test3(10));

        System.out.println(test4("anita lava la tina") ? "Palíndromo" : "No palíndromo");
    }

    /*
        1. Create a method that receives an array of 100,000 integers and outputs the frequency with which each integer appears in ascending order
     */
    private static String test1(int[] ints) {

        HashMap<String, Integer> hashMap = new HashMap<String, Integer>();
        for (int i = 0; i < ints.length; i++) {
            Integer N = ints[i];
            String n = N.toString();
            if (!hashMap.containsKey(n)) {
                hashMap.put(n, 0);
            }
            hashMap.put(n, hashMap.get(n) + 1);
        }

        Map<String, Integer> map = new TreeMap<String, Integer>(hashMap);

        String[] key = new String[map.size()];

        // array to store values of the HashMap
        Integer[] value = new Integer[map.size()];

        int i = 0;

        for (Map.Entry<String, Integer> entry : hashMap.entrySet()) {
            key[i] = entry.getKey();
            value[i++] = entry.getValue();
        }

        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("[");
        for (i = 0; i < hashMap.size(); i++)
            stringBuilder.append(" [" + key[i] + "," + value[i] + "]");
        stringBuilder.append(" ]");
        return stringBuilder.toString();
    }

    /*
        2. Write a simple algorithm that prints numbers from 1 to 200. If the number is a multiple of 3, print "Blue" next to the number,
        if the number is a multiple of 5 it print "Red", if the number is a multiple of both 3 and 5 it print "BlueRed".
    */
    private static void test2() {
        for (int i = 1; i <= 200; i++) {
            boolean multipleOf3 = i % 3 == 0;
            boolean multipleOf5 = i % 5 == 0;
            System.out.println(i + (multipleOf3 && multipleOf5 ? " BlueRed" : (multipleOf3 ? " Blue" : (multipleOf5 ? " Red" : ""))));
        }
    }

    /*
        3. Enter the function to calculate the factorial of an integer
    */
    private static int test3(int factorial) {
        int result;
        if (factorial == 0 || factorial == 1)
            return 1;

        result = test3(factorial - 1) * factorial;
        return result;
    }

    /*
        4. Create a method for determinate when a word or number is palindrome
    */
    public static boolean test4(String sentence) {
        char[] chars = sentence.replace(" ", "").toCharArray();
        int start = 0;
        int end = chars.length - 1;
        while (end > start) {
            if (chars[start] != chars[end]) {
                return false;
            }
            ++start;
            --end;
        }
        return true;
    }
}