Example added for BAEL-3083

core-java-modules/core-java-collections-list-2/src/main/java/com/baeldung/findastring/FindAStringInGivenList.java

@@ -0,0 +1,79 @@
+package com.baeldung.findastring;
+
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import org.apache.commons.collections4.CollectionUtils;
+import org.apache.commons.collections4.IterableUtils;
+import org.apache.commons.collections4.IteratorUtils;
+import org.apache.commons.collections4.PredicateUtils;
+import org.apache.commons.lang3.StringUtils;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+public class FindAStringInGivenList {
+
+
+    public List findUsingLoopWithRegex(String search, List<String> list) {
+
+        List<String> matches = new ArrayList<String>();
+
+        String pattern = ".*\\b"+search+"\\b.*";
+        Pattern p = Pattern.compile(pattern);
+
+        for(String str: list) {
+            if (p.matcher(str).matches()) {
+                matches.add(str);
+            }
+        }
+
+        return matches;
+    }
+
+
+    public List findUsingLoop(String search, List<String> list) {
+
+        List<String> matches = new ArrayList<String>();
+
+        for(String str: list) {
+            if (search != null && str.contains(search)) {
+                matches.add(str);
+            }
+        }
+
+        return matches;
+    }
+
+    public List findUsingStream(String search, List<String> list) {
+
+        List<String> matchingElements =
+                list.stream()
+                        .filter(str -> search != null)
+                        .filter(str -> str.trim().contains(search))
+                        .collect(Collectors.toList());
+
+        return matchingElements;
+    }
+
+    public List<String> findUsingGuava(String search, List<String> list) {
+        if (search == null) return Lists.newArrayList();
+
+        Iterable<String> result = Iterables.filter(Iterables.filter(list,Predicates.notNull()), Predicates.containsPattern(search));
+
+        return Lists.newArrayList(result.iterator());
+    }
+
+    public List<String> findUsingApacheCommon(String search, List<String> list) {
+        CollectionUtils.filter(list, PredicateUtils.notNullPredicate());
+        Iterable<String> result = IterableUtils.filteredIterable(list, new org.apache.commons.collections4.Predicate<String>() {
+            public boolean evaluate(String listElement) {
+                return search != null && StringUtils.isNotEmpty(listElement) ? listElement.contains(search) : false;
+            }
+        });
+
+        return IteratorUtils.toList(result.iterator());
+    }
+
+}

core-java-modules/core-java-collections-list-2/src/test/java/com/baeldung/findastring/FindAStringInListUnitTest.java

@@ -0,0 +1,93 @@
+package com.baeldung.findastring;
+
+import java.util.ArrayList;
+import java.util.List;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.Test;
+public class FindAStringInListUnitTest {
+
+    private static List<String> list = new ArrayList<>();
+
+    static {
+        list.add("Jack and Jill");
+        list.add("James and Sarah");
+        list.add("Sam and Louise");
+        list.add("Jack");
+        list.add(null);
+        list.add("");
+    }
+
+    private static FindAStringInGivenList findAStringInGivenList = new FindAStringInGivenList();
+
+    @Test
+    public void givenAString_whenFoundUsingLoopWithRegex_thenReturnList() {
+        List matchingElements = findAStringInGivenList.findUsingLoopWithRegex("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenNullFoundUsingLoopWithRegex_thenReturnEmptyList(){
+        List matchingElements = findAStringInGivenList.findUsingLoopWithRegex(null, list);
+        assertEquals(0, matchingElements.size());
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingLoop_thenReturnList() {
+        List matchingElements = findAStringInGivenList.findUsingLoop("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenNullFoundUsingLoop_thenReturnEmptyList(){
+        List matchingElements = findAStringInGivenList.findUsingLoop(null, list);
+        assertEquals(0, matchingElements.size());
+    }
+
+
+    @Test
+    public void givenAString_whenFoundUsingStream_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingStream("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenNullFoundUsingStream_thenReturnEmptyList(){
+        List matchingElements = findAStringInGivenList.findUsingStream(null, list);
+        assertEquals(0, matchingElements.size());
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingApacheCommons_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingApacheCommon("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenNullFoundUsingApacheCommons_thenReturnEmptyList(){
+        List matchingElements = findAStringInGivenList.findUsingApacheCommon(null, list);
+        assertEquals(0, matchingElements.size());
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingGuava_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingGuava("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenNullFoundUsingGuava_thenReturnEmptyList(){
+        List matchingElements = findAStringInGivenList.findUsingGuava(null, list);
+        assertEquals(0, matchingElements.size());
+    }
+
+}