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.

///

 * governing permissions and limitations under the License.
 */
package org.codelibs.fess.suggest.util;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Utility class for type-safe value extraction from Map objects.
 * Centralizes map access patterns to reduce code duplication and improve type safety.
 *

import java.io.IOException;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

import org.codelibs.core.exception.IORuntimeException;
import org.codelibs.core.log.Logger;

/**
 * Utility class for handling {@link java.util.zip.ZipInputStream}.
 *
 * @author koichik
 */
public abstract class ZipInputStreamUtil {

    private static final Logger logger = Logger.getLogger(ZipInputStreamUtil.class);

        transport = new SmbTransportImpl(ctx, address, 445, null, 0, false);

        // Reset MID to a known starting point for deterministic behavior
        setField(transport, "mid", new AtomicLong());
    }

    // Utility: reflectively set a private/protected field (searches up the hierarchy)
    private static void setField(Object target, String name, Object value) {
        try {
            Field f = findField(target.getClass(), name);

 * witch is initialized using system properties.
 *
 */
public class Config {

    /**
     * Private constructor to prevent instantiation of this utility class.
     */
    private Config() {
        // Utility class - not instantiable
    }

    private static final Logger log = LoggerFactory.getLogger(Config.class);

    /**

 */
package org.codelibs.fess.util;

import java.util.regex.Pattern;

import org.codelibs.fess.Constants;
import org.codelibs.fess.mylasta.direction.FessConfig;

/**
 * This class provides system-related utility methods.
 * It extends {@link org.codelibs.core.lang.SystemUtil} and adds
 * methods specific to the Fess application.
 */
public class SystemUtil extends org.codelibs.core.lang.SystemUtil {

 */

package com.google.common.base;

import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

/** Static utility method for unchecked throwing of any {@link Throwable}. */
@GwtCompatible
final class SneakyThrows<T extends Throwable> {
  /**
   * Throws {@code t} as if it were an unchecked {@link Throwable}.
   *

import com.google.common.annotations.J2ktIncompatible;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import org.jspecify.annotations.Nullable;

/**
 * Utility {@link RemovalListener} implementations intended for use in testing.
 *
 * @author mike nonemacher
 */
@GwtCompatible
final class TestingRemovalListeners {

  /** Returns a new no-op {@code RemovalListener}. */

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import org.codelibs.core.exception.IORuntimeException;

/**
 * Utility class for {@link InputStream}.
 *
 * @author higa
 */
public abstract class InputStreamUtil {

    /**
     * Do not instantiate.
     */
    protected InputStreamUtil() {
    }

import javax.xml.transform.Source;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;

import org.codelibs.core.exception.SAXRuntimeException;
import org.xml.sax.SAXException;

/**
 * Utility class for {@link Schema}.
 *
 * @author koichik
 */
public abstract class SchemaUtil {

    /**
     * Do not instantiate.
     */
    protected SchemaUtil() {
    }

    /**