Hamcrest matcher for a sublist/partial match?

Question

Say I have an actual List [1, 2, 3, 4] and I want to check if it contains the sub-list [2, 3] (i.e. order is also important). Is there an existing matcher that does this?

(There's a poorly-named hasItems method which only checks the actual list matches any one item in the expected list....)

Answer 1

Write your own if you can.

see Writing custom matchers

It should be something like:

 public class HasSublist<T> extends TypeSafeMatcher<T> {

     @Override
      public boolean matchesSafely(List<T> subList) {
        //Logic if sublist exist ...
        return true;
      }

      public static <T> Matcher<T> hasSubList(List<T> containsSublist) {
        return new HasSublist<T>(containsSublist);
      }
}

Answer 2

I think there is no such predefined Matcher. I'm using AssertJ on top of JUnit so I can address this case like this:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.assertj.core.api.Assertions;
import org.junit.Test;

public class TestContains2 {

  @Test
  public void test_contains() {
    List<Integer> a = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
    Assertions
      .assertThat(a)
      .containsSequence(2, 3);
  }
}