# 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

* The user types the `username` and `password` in the frontend, and hits `Enter`.
* The frontend (running in the user's browser) sends that `username` and `password` to a specific URL in our API (declared with `tokenUrl="token"`).
* The API checks that `username` and `password`, and responds with a "token" (we haven't implemented any of this yet).

import java.lang.annotation.Target;

/**
 * Disables Animal Sniffer's checking of compatibility with older versions of Java/Android.
 *
 * <p>Each package's copy of this annotation needs to be listed in our {@code pom.xml}.
 */
@Target({METHOD, CONSTRUCTOR, TYPE, FIELD})

import java.lang.annotation.Target;

/**
 * Disables Animal Sniffer's checking of compatibility with older versions of Java/Android.
 *
 * <p>Each package's copy of this annotation needs to be listed in our {@code pom.xml}.
 */
@Target({METHOD, CONSTRUCTOR, TYPE, FIELD})

* find the module `dependencies` (an imaginary file at `app/routers/dependencies.py`)...
* and from it, import the function `get_token_header`.

But that file doesn't exist, our dependencies are in a file at `app/dependencies.py`.

Remember how our app/file structure looks like:

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

---

The two dots `..`, like in:

```Python

 * limitations under the License.
 */

package com.google.common;

import com.google.gwt.core.client.EntryPoint;

/**
 * A dummy entry point to convince Maven to compile our classes.
 *
 * @author Chris Povirk
 */
public class ForceGuavaCompilationEntryPoint implements EntryPoint {
  @Override
  public void onModuleLoad() {}

  }

  public Test testsForLinkedList() {
    return QueueTestSuiteBuilder.using(
            new TestStringQueueGenerator() {
              @Override
              // We are testing LinkedList / testing our tests on LinkedList.
              @SuppressWarnings("JdkObsolete")
              public Queue<String> create(String[] elements) {
                return new LinkedList<>(MinimalCollection.of(elements));
              }

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the