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How to Encrypt Words in Java

The challenge

You want to create secret messages which must be deciphered.

Here are the conditions:

  1. Your message is a string containing space separated words.
  2. You need to encrypt each word in the message using the following rules:
    • The first letter must be converted to its ASCII code.
    • The second letter must be switched with the last letter
  3. Keepin’ it simple: There are no special characters in the input.


EncryptWords.encryptThis("Hello") => "72olle" EncryptWords.encryptThis("good") => "103doo" EncryptWords.encryptThis("hello world") => "104olle 119drlo"
Code language: PHP (php)

The solution in Java code

Option 1:

import java.util.Arrays; import java.util.Iterator; public class EncryptWords { public static String encryptThis(String text) { if (text.length()==) return ""; String[] words = text.split(" "); StringBuilder sb = new StringBuilder(); for (Iterator<String> it =; it.hasNext(); ) { String word =; StringBuilder nw = new StringBuilder(); //first char nw.append((int)word.charAt()); if (word.length()>1) { //last char nw.append(word.charAt(word.length() - 1)); //rest of word if (word.length()>=3) nw.append(word.substring(2, word.length() - 1)); //second char if (word.length()>2) nw.append(word.charAt(1)); } //add to main word sb.append(nw).append(" "); } return sb.toString().trim(); } }
Code language: Java (java)

Option 2:

import java.util.Arrays; import; public class EncryptWords { public static String encryptThis(String text) { return" ")) .map(w->w.length()>2?(int)w.charAt()+w.substring(w.length()-1)+w.substring(2, w.length()-1)+w.substring(1,2): w.length()>1?(int)w.charAt()+w.substring(1): w.length()==1?(int)w.charAt()+"":"") .collect(Collectors.joining(" ")); } }
Code language: Java (java)

Option 3:

import java.util.Arrays; import; public class EncryptWords { public static String encryptThis(String text) { return text.length() == ? text :" ")) .map(s -> "" + (int) s.charAt() + (s.length() > 2 ? s.charAt(s.length() - 1) + s.substring(2, s.length() - 1) + s.charAt(1) : s.substring(1))) .collect(Collectors.joining(" ")); } }
Code language: Java (java)

Test cases to validate our solution

import org.junit.jupiter.api.Test; import static org.junit.jupiter.api.Assertions.*; public class EncryptWordsTest { @Test public void exampleTests() { assertEquals("", EncryptWords.encryptThis("")); assertEquals("65 119esi 111dl 111lw 108dvei 105n 97n 111ka", EncryptWords.encryptThis("A wise old owl lived in an oak")); assertEquals("84eh 109ero 104e 115wa 116eh 108sse 104e 115eokp", EncryptWords.encryptThis("The more he saw the less he spoke")); assertEquals("84eh 108sse 104e 115eokp 116eh 109ero 104e 104dare", EncryptWords.encryptThis("The less he spoke the more he heard")); assertEquals("87yh 99na 119e 110to 97ll 98e 108eki 116tah 119esi 111dl 98dri", EncryptWords.encryptThis("Why can we not all be like that wise old bird")); assertEquals("84kanh 121uo 80roti 102ro 97ll 121ruo 104ple", EncryptWords.encryptThis("Thank you Piotr for all your help")); } }
Code language: Java (java)

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