[BAEL-3488] Timer Class (#8769)

* [BAEL-3488] Moving code to core-java where the original article code was located

* [BAEL-3488] Moved original code under timer package

core-java-modules/core-java/src/main/java/com/baeldung/timer/DatabaseMigrationTask.java

@@ -0,0 +1,19 @@
+package com.baeldung.timer;
+
+import java.util.List;
+import java.util.TimerTask;
+
+public class DatabaseMigrationTask extends TimerTask {
+    private List<String> oldDatabase;
+    private List<String> newDatabase;
+
+    public DatabaseMigrationTask(List<String> oldDatabase, List<String> newDatabase) {
+        this.oldDatabase = oldDatabase;
+        this.newDatabase = newDatabase;
+    }
+
+    @Override
+    public void run() {
+        newDatabase.addAll(oldDatabase);
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/timer/NewsletterTask.java

@@ -0,0 +1,14 @@
+package com.baeldung.timer;
+
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.TimerTask;
+
+public class NewsletterTask extends TimerTask {
+    @Override
+    public void run() {
+        System.out.println("Email sent at: "
+          + LocalDateTime.ofInstant(Instant.ofEpochMilli(scheduledExecutionTime()), ZoneId.systemDefault()));
+    }
+}