[JAVA-13962] Align code with article + clean up (#13012)

* [JAVA-13962] Align code with article + clean up

* [JAVA-13962] Clean up

Co-authored-by: panagiotiskakos <panagiotis.kakos@libra-is.com>

core-java-modules/core-java-concurrency-basic/src/main/java/com/baeldung/concurrent/executorservice/DelayedCallable.java

@@ -0,0 +1,40 @@
+package com.baeldung.concurrent.executorservice;
+
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.CountDownLatch;
+
+public class DelayedCallable implements Callable<String> {
+
+    private String name;
+    private long period;
+    private CountDownLatch latch;
+
+    public DelayedCallable(String name, long period, CountDownLatch latch) {
+        this(name, period);
+        this.latch = latch;
+    }
+
+    public DelayedCallable(String name, long period) {
+        this.name = name;
+        this.period = period;
+    }
+
+    public String call() {
+
+        try {
+            Thread.sleep(period);
+
+            if (latch != null) {
+                latch.countDown();
+            }
+
+        } catch (InterruptedException ex) {
+            // handle exception
+            ex.printStackTrace();
+            Thread.currentThread().interrupt();
+        }
+
+        return name;
+    }
+}