These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

/**
 * Utility class for calculating and verifying PAC (Privilege Attribute Certificate) message authentication codes.
 * This class provides methods for computing MACs using various Kerberos encryption types including
 * ARCFOUR-HMAC-MD5 and AES-based HMAC algorithms.
 */
public class PacMac {

    /**
     * Private constructor to prevent instantiation of utility class.
     */
    private PacMac() {

import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;

import jcifs.BaseTest;

/**
 * Test class for Encdec utility functionality
 */
@DisplayName("Encdec Utility Tests")
class EncdecTest extends BaseTest {

    @Test
    @DisplayName("Should encode and decode 16-bit integers")
    void testInt16Operations() {
        // Given

{
  "name": "Hacking Gopher",
  "version": "1.0",
  "manifest_version": 2,
  "description": "Go Hacking utility",
  "background": {
    "page": "background.html"
  },
  "browser_action": {
    "default_icon": "gopher.png",
    "default_popup": "popup.html"
  },
  "omnibox": { "keyword": "golang" },
  "icons": {
    "16": "gopher.png"
  },
  "permissions": [
     "tabs"
  ]

import org.opensearch.core.xcontent.ToXContent;
import org.opensearch.core.xcontent.XContentBuilder;
import org.opensearch.core.xcontent.XContentHelper;
import org.opensearch.search.SearchHit;

/**
 * Utility class for search engine operations and content formatting.
 * Provides helper methods for working with XContent builders, scrolling through search results,
 * and converting XContent objects to different output formats.
 */

import java.util.Collections;
import java.util.Map;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Stream;

/**
 * Utility class for {@link Stream}.
 */
public abstract class StreamUtil {
    protected StreamUtil() {
        // nothing
    }

    /**
     * Creates a {@link StreamOf} instance from the provided values.

import org.jspecify.annotations.Nullable;

/**
 * A utility for testing an Iterator implementation by comparing its behavior to that of a "known
 * good" reference implementation. In order to accomplish this, it's important to test a great
 * variety of sequences of the {@link Iterator#next}, {@link Iterator#hasNext} and {@link
 * Iterator#remove} operations. This utility takes the brute-force approach of trying <i>all</i>

        builder.put(i, elements[i]);
      }
      return builder.build().values().asList();
    }
  }

  /**
   * Useless constructor for a class of static utility methods.
   *
   * @deprecated Do not instantiate this utility class.
   */
  @Deprecated
  public SortedMapGenerators() {}

import org.lastaflute.web.util.LaRequestUtil;

import jakarta.servlet.http.HttpServletRequest;

/**
 * Utility class for document data manipulation and type conversion.
 * This class provides static methods for extracting typed values from document maps,
 * URL encoding, and other document-related operations. It's designed as a final
 * utility class with only static methods.
 *
 */
public final class DocumentUtil {

    /**

import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;

import jcifs.BaseTest;

/**
 * Test class for Hexdump utility functionality
 */
@DisplayName("Hexdump Utility Tests")
class HexdumpTest extends BaseTest {

    @Test
    @DisplayName("Should convert byte array to hex string")
    void testToHexString() {
        // Given