Java Intermediate: 07/01/2021

Main.java

package com.javafx.test;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a password to check if it's valid: ");
        String str123 = scanner.nextLine();
        System.out.println();
        isValid(str123);

        System.out.print("Enter a word to check if it's a palindrome: ");
        String word = scanner.nextLine().trim().toLowerCase();
        palindrome(word);

        System.out.print("Enter a sentence to reverse the characters in each word: ");
        String str = scanner.nextLine();
        wordReverse(str);

        System.out.print("Enter a string to concatenate with itself: ");
        String str1 = scanner.nextLine();
        System.out.print("Enter a number of times to concatenate it: ");
        int int1 = scanner.nextInt();
        String resultV1 = repeat_str(str1, int1);
        System.out.println("\nAfter repeating "+int1+" times: "+resultV1);

        System.out.println("Average of 3 numbers: "+ avg(5,10,15));
    }
    public static void wordReverse(String str){
        String[] words = str.split(" ");
        String reversedString = "";
        for (int i = 0; i < words.length; i++)
        {
            String word = words[i];
            String reverseWord = "";
            for (int j = word.length()-1; j >= 0; j--)
            {
                /* The charAt() function returns the character
                 * at the given position in a string
                 */
                reverseWord = reverseWord + word.charAt(j);
            }
            reversedString = reversedString + reverseWord + " ";
        }
        System.out.println(reversedString);
    }
    public static void palindrome(String word){
        int low = 0; // low index of the word
        int high = word.length() - 1; // high index of the word
        boolean isPalindrome = true;

        if (word.isEmpty()) {
            isPalindrome = false;
        } else {
            while (low < high) {
                // check if chars at low and high indices are matching
                if (word.charAt(low) != word.charAt(high)) {
                    isPalindrome = false;
                    break;
                }
                low++;
                high--;
            }
        }

        if (isPalindrome) {
            System.out.println("The word is a palindrome.");
        } else {
            System.out.println("The word is NOT a palindrome.");
        }
    }
    public static String repeat_str(String str1, int n) {
        if (str1 == null || str1.isEmpty()) {
            return "";
        }
        if (n <= 0) {
            return str1;
        }
        String newString = "";
        for(int i = 1; i <= n; i++){
            newString = newString + str1;
        }

        return newString;
    }
    public static double avg(int a, int b, int c){
        int total = a+b+c;
        double average = total/3;
        return average;
    }
    public static void isValid(String password)
    {
        boolean valid = true;
        // for checking if password length
        // is between 8 and 15
        if (!((password.length() >= 8)
                )) {
            valid = false;
        }

        // to check space
        if (password.contains(" ")) {
            valid = false;
        }
        if (true) {
            int count = 0;

            // check digits from 0 to 9
            for (int i = 0; i <= 9; i++) {

                // to convert int to string
                String str1 = Integer.toString(i);

                if (password.contains(str1)) {
                    count = 1;
                }
            }
            if (count == 0) {
                valid = false;
            }
        }

        // for special characters
        if (!(password.contains("@") || password.contains("#")
                || password.contains("!") || password.contains("~")
                || password.contains("$") || password.contains("%")
                || password.contains("^") || password.contains("&")
                || password.contains("*") || password.contains("(")
                || password.contains(")") || password.contains("-")
                || password.contains("+") || password.contains("/")
                || password.contains(":") || password.contains(".")
                || password.contains(", ") || password.contains("<")
                || password.contains(">") || password.contains("?")
                || password.contains("|"))) {
            valid = false;
        }

        // if all conditions fails
        if(valid){
            System.out.println("This password is valid");
        }
        else {
            System.out.println("This password is not valid");
        }
    }
}