# ADR-0008 - Use NullAway for null checking

## Date

2025-08-06

## Context

Our codebase uses `null` extensively to represent an absence of value or optionality of the argument.
We utilize nullness annotations in Java code and somewhat rely on IDE warnings to guide us.
However, the Java code we have is not fully annotated, which causes several consequences:
* IDE warnings can be misleading

        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() {}

package com.google.common.testing;

import com.google.common.annotations.GwtCompatible;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jspecify.annotations.NullMarked;

/**
 * Simple utility for when you want to create a {@link TearDown} that may throw an exception but
 * should not fail a test when it does. (The behavior of a {@code TearDown} that throws an exception

 * governing permissions and limitations under the License.
 */
package org.codelibs.core.misc;

import java.util.Locale;
import java.util.function.Supplier;

/**
 * Utility class for {@link Locale}.
 *
 * @author higa
 */
public abstract class LocaleUtil {

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

    /**

 * under the License.
 */
package org.apache.maven.project;

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

/**
 * Provides metadata about a build extension. <strong>Warning:</strong> This is an internal utility class that is only
 * public for technical reasons, it is not part of the public API. In particular, this class can be changed or deleted
 * without prior notice.
 *
 */
public class ExtensionDescriptor {

import java.io.InputStream;
import java.net.URLConnection;

import org.codelibs.core.exception.IORuntimeException;
import org.codelibs.core.io.CloseableUtil;
import org.codelibs.core.io.ResourceUtil;

/**
 * Utility class for MIME types.
 *
 * @author shot
 */
public abstract class MimeTypeUtil {

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

    /**

import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotNull;

import java.text.DecimalFormatSymbols;
import java.util.Locale;
import java.util.Map;

import org.codelibs.core.misc.LocaleUtil;

/**
 * Utility class for {@link DecimalFormatSymbols}.
 *
 * @author higa
 */
public abstract class DecimalFormatSymbolsUtil {

    private static final Map<Locale, DecimalFormatSymbols> CACHE = newConcurrentHashMap();

    /**

 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.codelibs.core.convert;

/**
 * Utility class for conversions related to {@link Boolean}.
 *
 * @author higa
 */
public abstract class BooleanConversionUtil {

    /**
     * Do not instantiate.
     */
    protected BooleanConversionUtil() {

    public Collection<Integer>[] createValueArray(int length) {
      return new ImmutableSet[length];
    }
  }

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

 */
package org.codelibs.core.net;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.SecureRandom;

import org.codelibs.core.lang.StringUtil;

/**
 * Utility for creating UUIDs.
 *
 * @author higa
 */
public abstract class UuidUtil {

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