checkCanReserializeSingleton(Functions.toStringFunction());
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointerExceptions() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicStaticMethods(Functions.class);
  }

  public void testForMapWithoutDefault() {
    Map<String, @Nullable Integer> map = new HashMap<>();
    map.put("One", 1);
    map.put("Three", 3);

        .createTestSuite();
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointerExceptions() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicStaticMethods(Collections2.class);
  }

  public void testOrderedPermutationSetEmpty() {
    List<Integer> list = new ArrayList<>();

## Website

[fess.codelibs.org](https://fess.codelibs.org/)

## Issues/Questions

[discuss.codelibs.org](https://discuss.codelibs.org/c/FessEN/)

## Getting Started

There are 2 ways to try Fess. The first is to download and install yourself. The second is to use [Docker](https://www.docker.com/products/docker-engine).

### Download and Install/Run

      Work (including but not limited to damages for loss of goodwill,
      work stoppage, computer failure or malfunction, or any and all
      other commercial damages or losses), even if such Contributor
      has been advised of the possibility of such damages.

   9. Accepting Warranty or Additional Liability. While redistributing

import java.util.List;
import java.util.Objects;
import java.util.function.BiPredicate;
import java.util.stream.Collector;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Tester for {@code Collector} implementations.
 *
 * <p>Example usage:
 *
 * <pre>
 * CollectorTester.of(Collectors.summingInt(Integer::parseInt))
 *     .expectCollects(3, "1", "2")

      Work (including but not limited to damages for loss of goodwill,
      work stoppage, computer failure or malfunction, or any and all
      other commercial damages or losses), even if such Contributor
      has been advised of the possibility of such damages.

   9. Accepting Warranty or Additional Liability. While redistributing

      Work (including but not limited to damages for loss of goodwill,
      work stoppage, computer failure or malfunction, or any and all
      other commercial damages or losses), even if such Contributor
      has been advised of the possibility of such damages.

   9. Accepting Warranty or Additional Liability. While redistributing

      Work (including but not limited to damages for loss of goodwill,
      work stoppage, computer failure or malfunction, or any and all
      other commercial damages or losses), even if such Contributor
      has been advised of the possibility of such damages.

   9. Accepting Warranty or Additional Liability. While redistributing

      Work (including but not limited to damages for loss of goodwill,
      work stoppage, computer failure or malfunction, or any and all
      other commercial damages or losses), even if such Contributor
      has been advised of the possibility of such damages.

   9. Accepting Warranty or Additional Liability. While redistributing

## Website

[fess.codelibs.org](https://fess.codelibs.org/)

## Probleme/Fragen

[discuss.codelibs.org](https://discuss.codelibs.org/c/FessEN/)

## Erste Schritte