package com.baeldung.joinpoint; import org.apache.commons.lang3.StringUtils; import org.springframework.stereotype.Service; import java.util.Arrays; import java.util.List; import static java.util.stream.Collectors.toList; @Service public class ArticleService { public List getArticleList() { return Arrays.asList( "Article 1", "Article 2" ); } public List getArticleList(String startsWithFilter) { if (StringUtils.isBlank(startsWithFilter)) { throw new IllegalArgumentException("startsWithFilter can't be blank"); } return getArticleList() .stream() .filter(a -> a.startsWith(startsWithFilter)) .collect(toList()); } }