BAEL-7356 Code for the Morse Code Translation in Java article

core-java-modules/core-java-string-operations-7/pom.xml

@@ -39,6 +39,11 @@
             <artifactId>icu4j</artifactId>
             <version>${icu4j.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${apache.commons.collection.version}</version>
+        </dependency>        
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>
@@ -75,6 +80,7 @@
         <maven.compiler.source>11</maven.compiler.source>
         <maven.compiler.target>11</maven.compiler.target>
         <apache.commons.lang3.version>3.13.0</apache.commons.lang3.version>
+        <apache.commons.collection.version>4.4</apache.commons.collection.version>        
         <apache.tika.version>2.9.1</apache.tika.version>
         <commons-text.version>1.10.0</commons-text.version>
         <icu4j.version>74.1</icu4j.version>

core-java-modules/core-java-string-operations-7/src/main/java/com/baeldung/morse/MorseTranslator.java

@@ -0,0 +1,103 @@
+package com.baeldung.morse;
+
+import org.apache.commons.collections4.BidiMap;
+import org.apache.commons.collections4.bidimap.DualHashBidiMap;
+
+public class MorseTranslator {
+
+    private static final BidiMap<String, String> morseAlphabet = new DualHashBidiMap<>();
+
+    static {
+        morseAlphabet.put("A", ".-");
+        morseAlphabet.put("B", "-...");
+        morseAlphabet.put("C", "-.-.");
+        morseAlphabet.put("D", "-..");
+        morseAlphabet.put("E", ".");
+        morseAlphabet.put("F", "..-.");
+        morseAlphabet.put("G", "--.");
+        morseAlphabet.put("H", "....");
+        morseAlphabet.put("I", "..");
+        morseAlphabet.put("J", ".---");
+        morseAlphabet.put("K", "-.-");
+        morseAlphabet.put("L", ".-..");
+        morseAlphabet.put("M", "--");
+        morseAlphabet.put("N", "-.");
+        morseAlphabet.put("O", "---");
+        morseAlphabet.put("P", ".--.");
+        morseAlphabet.put("Q", "--.-");
+        morseAlphabet.put("R", ".-.");
+        morseAlphabet.put("S", "...");
+        morseAlphabet.put("T", "-");
+        morseAlphabet.put("U", "..-");
+        morseAlphabet.put("V", "...-");
+        morseAlphabet.put("W", ".--");
+        morseAlphabet.put("X", "-..-");
+        morseAlphabet.put("Y", "-.--");
+        morseAlphabet.put("Z", "--..");
+        morseAlphabet.put("0", "-----");
+        morseAlphabet.put("1", ".----");
+        morseAlphabet.put("2", "..---");
+        morseAlphabet.put("3", "...--");
+        morseAlphabet.put("4", "....-");
+        morseAlphabet.put("5", ".....");
+        morseAlphabet.put("6", "-....");
+        morseAlphabet.put("7", "--...");
+        morseAlphabet.put("8", "---..");
+        morseAlphabet.put("9", "----.");
+        morseAlphabet.put(".", ".-.-.-");
+        morseAlphabet.put(",", "--..--");
+        morseAlphabet.put("?", "..--..");
+        morseAlphabet.put("'", ".----.");
+        morseAlphabet.put("!", "-.-.-----.");
+        morseAlphabet.put("/", "-..-.");
+        morseAlphabet.put("(", "-.--.");
+        morseAlphabet.put(")", "-.--.-");
+        morseAlphabet.put("&", ".-...");
+        morseAlphabet.put(":", "---...");
+        morseAlphabet.put(";", "-.-.-.");
+        morseAlphabet.put("=", "-...-");
+        morseAlphabet.put("+", ".-.-.");
+        morseAlphabet.put("-", "-....-");
+        morseAlphabet.put("_", "..--.-");
+        morseAlphabet.put("\"", ".-..-.");
+        morseAlphabet.put("$", "...-..-");
+        morseAlphabet.put("@", ".--.-.");
+        morseAlphabet.put(" ", "/");
+    }
+
+    static String englishToMorse(String english) {
+        if (english == null) {
+            return null;
+        }
+        String upperCaseEnglish = english.toUpperCase();
+        String[] morse = new String[upperCaseEnglish.length()];
+        for (int index = 0; index < upperCaseEnglish.length(); index++) {
+            String morseCharacter = morseAlphabet.get(String.valueOf(upperCaseEnglish.charAt(index)));
+            if (morseCharacter == null) {
+                throw new IllegalArgumentException("Character " + upperCaseEnglish.charAt(index) + " can't be translated to morse");
+            }
+            morse[index] = morseCharacter;
+        }
+        return String.join(" ", morse);
+    }
+
+    static String morseToEnglish(String morse) {
+        if (morse == null) {
+            return null;
+        }
+        if (morse.isEmpty()) {
+            return "";
+        }
+        String[] morseUnitCharacters = morse.split(" ");
+        StringBuilder stringBuilder = new StringBuilder();
+        for (int index = 0; index < morseUnitCharacters.length; index ++) {
+            String englishCharacter = morseAlphabet.getKey(morseUnitCharacters[index]);
+            if (englishCharacter == null) {
+                throw new IllegalArgumentException("Character " + morseUnitCharacters[index] + " is not a valid morse character");
+            }
+            stringBuilder.append(englishCharacter);
+        }
+        return stringBuilder.toString();
+    }
+
+}

core-java-modules/core-java-string-operations-7/src/test/java/com/baeldung/morse/MorseTranslatorUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.morse;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class MorseTranslatorUnitTest {
+
+    @ParameterizedTest
+    @ValueSource(strings = {"MORSE CODE!", "morse code!", "mOrSe cOdE!"})
+    void givenAValidEnglishWordWhateverTheCapitalization_whenEnglishToMorse_thenTranslatedToMorse(String english) {
+        assertEquals("-- --- .-. ... . / -.-. --- -.. . -.-.-----.", MorseTranslator.englishToMorse(english));
+    }
+
+    @Test
+    void givenAnEnglishWordWithAnIllegalCharacter_whenEnglishToMorse_thenThrows() {
+        String english = "~This sentence starts with an illegal character";
+        assertThrows(IllegalArgumentException.class, () -> MorseTranslator.englishToMorse(english));
+    }
+
+    @Test
+    void givenNull_whenEnglishToMorse_thenNull() {
+        assertNull(MorseTranslator.englishToMorse(null));
+    }
+
+    @Test
+    void givenEmptyString_whenEnglishToMorse_thenEmptyArray() {
+        assertEquals("", MorseTranslator.englishToMorse(""));
+    }
+
+    @Test
+    void givenAValidMorseWord_whenMorseToEnglish_thenTranslatedToUpperCaseEnglish() {
+        assertEquals("MORSE CODE!", MorseTranslator.morseToEnglish("-- --- .-. ... . / -.-. --- -.. . -.-.-----."));
+    }
+
+    @Test
+    void givenAMorseWordWithAnIllegalCharacter_whenMorseToEnglish_thenThrows() {
+        assertThrows(IllegalArgumentException.class, () -> MorseTranslator.morseToEnglish(".!!!!!!!"));
+    }
+
+    @Test
+    void givenNull_whenMorseToEnglish_thenNull() {
+        assertNull(MorseTranslator.morseToEnglish(null));
+    }
+
+    @Test
+    void givenEmptyArray_whenMorseToEnglish_thenEmptyString() {
+        assertEquals("", MorseTranslator.morseToEnglish(""));
+    }
+
+}