Add Javadoc to CharUtils utility class

core/src/main/java/app/notesr/core/util/CharUtils.java

@@ -13,7 +13,28 @@
 import java.nio.charset.CharsetEncoder;
 import java.util.Arrays;
 
+/**
+ * Utility class for character and byte conversion operations with secure memory handling.
+ * 
+ * <p>This utility provides methods to convert between character and byte arrays using
+ * specified charsets, with automatic memory cleanup to minimize sensitive data exposure.
+ * All buffers are securely cleared after use to prevent information leakage.
+ */
 public final class CharUtils {
+    /**
+     * Converts a character array to a byte array using the specified charset.
+     * 
+     * <p>This method encodes the given character array to bytes using the provided charset.
+     * Both the character buffer and byte buffer are securely cleared after extraction to
+     * minimize sensitive data exposure in memory.
+     * 
+     * @param chars the character array to convert. May be {@code null}.
+     * @param charset the charset to use for encoding
+     * @return a new byte array containing the encoded bytes, or {@code null} if the
+     *         input character array is {@code null}
+     * @throws CharacterCodingException if the character sequence cannot be encoded
+     *         using the specified charset
+     */
     public static byte[] charsToBytes(char[] chars, Charset charset)
             throws CharacterCodingException {
 
@@ -39,6 +60,20 @@ public static byte[] charsToBytes(char[] chars, Charset charset)
         return bytes;
     }
 
+    /**
+     * Converts a byte array to a character array using the specified charset.
+     * 
+     * <p>This method decodes the given byte array to characters using the provided charset.
+     * Both the byte buffer and character buffer are securely cleared after extraction to
+     * minimize sensitive data exposure in memory.
+     * 
+     * @param bytes the byte array to convert. May be {@code null}.
+     * @param charset the charset to use for decoding
+     * @return a new character array containing the decoded characters, or {@code null} if the
+     *         input byte array is {@code null}
+     * @throws CharacterCodingException if the byte sequence cannot be decoded
+     *         using the specified charset
+     */
     public static char[] bytesToChars(byte[] bytes, Charset charset)
             throws CharacterCodingException {
 
@@ -64,6 +99,17 @@ public static char[] bytesToChars(byte[] bytes, Charset charset)
         return chars;
     }
 
+    /**
+     * Checks whether the given character array contains any non-zero characters.
+     * 
+     * <p>This method iterates through the character array and returns {@code true} if
+     * any character is not the null character ({@code '\0'}). This is useful for
+     * determining if sensitive data (like passwords) still exists in memory.
+     * 
+     * @param chars the character array to check. May be {@code null}.
+     * @return {@code true} if the array contains at least one non-zero character,
+     *         {@code false} if the array is {@code null}, empty, or contains only null characters
+     */
     public static boolean hasNonZeroChars(char[] chars) {
         if (chars == null) {
             return false;