Add Base64Util with encode/decode and unit tests

Author: TonGonzalez

src/main/java/com/thealgorithms/conversions/Base64Util.java

@@ -0,0 +1,47 @@
+package com.thealgorithms.conversions;
+
+import java.util.Base64;
+
+/**
+ * Converts text to Base64 and Base64 back to text
+ *
+ * @author Ayrton Souza
+ */
+public final class Base64Util {
+
+    private Base64Util() {
+    }
+
+    /**
+     * Encodes a given string into Base64 format.
+     *
+     * @param input The text to be converted to Base64.
+     * @return Base64 representation of the input text.
+     * @throws IllegalArgumentException if input is null.
+     */
+    public static String encode(String input) {
+        if (input == null) {
+            throw new IllegalArgumentException("Input cannot be null");
+        }
+        return Base64.getEncoder().encodeToString(input.getBytes());
+    }
+
+    /**
+     * Decodes a Base64 string back to original text.
+     *
+     * @param base64 The Base64 encoded string.
+     * @return The decoded original text.
+     * @throws IllegalArgumentException if base64 is null or not a valid Base64 string.
+     */
+    public static String decode(String base64) {
+        if (base64 == null) {
+            throw new IllegalArgumentException("Input cannot be null");
+        }
+        try {
+            byte[] decodedBytes = Base64.getDecoder().decode(base64);
+            return new String(decodedBytes);
+        } catch (IllegalArgumentException e) {
+            throw new IllegalArgumentException("Invalid Base64 input", e);
+        }
+    }
+}

src/test/java/com/thealgorithms/conversions/Base64Test.java

@@ -0,0 +1,56 @@
+package com.thealgorithms.conversions;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+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.CsvSource;
+
+public class Base64Test{
+
+    @Test
+    // Test encoding and decoding normal strings
+    public void testEncodeAndDecode() {
+        String original = "Hello, World!";
+        String encoded = Base64Util.encode(original);
+        String decoded = Base64Util.decode(encoded);
+
+        assertEquals(original, decoded);
+    }
+
+    @Test
+    // Test encoding and decoding empty string
+    public void testEmptyString() {
+        String encoded = Base64Util.encode("");
+        String decoded = Base64Util.decode(encoded);
+
+        assertEquals("", decoded);
+    }
+
+    @Test
+    // Test encoding null input
+    public void testNullInputEncode() {
+        assertThrows(IllegalArgumentException.class, () -> Base64Util.encode(null));
+    }
+
+    @Test
+    // Test decoding null input
+    public void testNullInputDecode() {
+        assertThrows(IllegalArgumentException.class, () -> Base64Util.decode(null));
+    }
+
+    @ParameterizedTest
+    @CsvSource({
+            "invalid@@base64",
+            "12345$%",
+            "====",
+            "abc?def"
+    })
+        // Test decoding invalid Base64 strings
+    void testInvalidBase64Decode(String invalidBase64) {
+        assertThrows(IllegalArgumentException.class, () -> Base64Util.decode(invalidBase64));
+    }
+
+}
+