[call-a-method-oneach] call a method on each element (#15540)

* [call-a-method-oneach] call a method on each element

* [call-a-method-oneach] fix typo

core-java-modules/core-java-collections-list-6/src/test/java/com/baeldung/callmethodoneach/CallAMethodOnEachElementUnitTest.java

@@ -0,0 +1,96 @@
+package com.baeldung.callmethodoneach;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.Function;
+import com.google.common.collect.Lists;
+
+class Player {
+
+    private int id;
+    private String name;
+    private int score;
+
+    public Player(int id, String name, int score) {
+        this.id = id;
+        this.name = name;
+        this.score = score;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getScore() {
+        return score;
+    }
+}
+
+public class CallAMethodOnEachElementUnitTest {
+
+    private Logger log = LoggerFactory.getLogger(this.getClass());
+
+    // @formatter:off
+    private final static List<Player> PLAYERS = List.of(
+        new Player(1, "Kai", 42),
+        new Player(2, "Eric", 43),
+        new Player(3, "Saajan", 64),
+        new Player(4, "Kevin", 30),
+        new Player(5, "John", 5));
+    // @formatter:on
+
+    @Test
+    void whenUsingForLoopCallLogPrint_thenGetExpectedResult() {
+        for (Player p : PLAYERS) {
+            log.info(p.getName());
+        }
+    }
+
+    @Test
+    void whenUsingForEachCallLogPrint_thenGetExpectedResult() {
+        PLAYERS.forEach(player -> log.info(player.getName()));
+    }
+
+    @Test
+    void whenUsingForLoopAndListAddExtractPlayerNames_thenGetExpectedResult() {
+        List<String> names = new ArrayList<>();
+        for (Player p : PLAYERS) {
+            names.add(p.getName());
+        }
+        assertEquals(Arrays.asList("Kai", "Eric", "Saajan", "Kevin", "John"), names);
+    }
+
+    @Test
+    void whenUsingGuavaTransformExtractPlayerNames_thenGetExpectedResult() {
+        List<String> names = Lists.transform(PLAYERS, new Function<Player, String>() {
+            @Override
+            public String apply(Player input) {
+                return input.getName();
+            }
+        });
+
+        assertEquals(Arrays.asList("Kai", "Eric", "Saajan", "Kevin", "John"), names);
+    }
+
+    @Test
+    void whenUsingStreamMapExtractPlayerNames_thenGetExpectedResult() {
+        List<String> names = PLAYERS.stream()
+            .map(player -> player.getName())
+            .collect(Collectors.toList());
+        assertEquals(List.of("Kai", "Eric", "Saajan", "Kevin", "John"), names);
+    }
+
+}