[BAEL-820] Difference between wait() and sleep() in Java (#1708)

* injecting beans

* XML-based configuration replaced with Java Config.

* [BAEL-431] Exploring TestRestTemplate.

* Revert of evaluation task "XML-based configuration replaced with Java Config."

This reverts commit 66471cf0574c85f8ff514ec4caf5ba44ebba1a74.

* Revert of evaluation task "injecting beans"

This reverts commit d2ac20185e636245bc0ae0b4ccb952965de88e28.

* [BAEL-431] fix to the tests in TestRestTemplateBasicLiveTest.

* [BAEL-431] added more meaningful user and password for auth.

* [BAEL-820] examples of wait() and sleep() methods.

* [BAEL-820] wait() and sleep() examples.

core-java/src/main/java/com/baeldung/concurrent/sleepwait/ThreadA.java

@@ -0,0 +1,21 @@
+package com.baeldung.concurrent.sleepwait;
+
+/***
+ * Example of waking up a waiting thread
+ */
+public class ThreadA {
+    private static final ThreadB b = new ThreadB();
+
+    public static void main(String... args) throws InterruptedException {
+        b.start();
+
+        synchronized (b) {
+            while (b.sum == 0) {
+                System.out.println("Waiting for ThreadB to complete...");
+                b.wait();
+            }
+
+            System.out.println("ThreadB has completed. Sum from that thread is: " + b.sum);
+        }
+    }
+}

core-java/src/main/java/com/baeldung/concurrent/sleepwait/ThreadB.java

@@ -0,0 +1,20 @@
+package com.baeldung.concurrent.sleepwait;
+
+/***
+ * Example of waking up a waiting thread
+ */
+class ThreadB extends Thread {
+    int sum;
+
+    @Override
+    public void run() {
+        synchronized (this) {
+            int i = 0;
+            while (i < 100000) {
+                sum += i;
+                i++;
+            }
+            notify();
+        }
+    }
+}

core-java/src/main/java/com/baeldung/concurrent/sleepwait/WaitSleepExample.java

@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.sleepwait;
+
+/***
+ * Example of wait() and sleep() methods
+ */
+public class WaitSleepExample {
+    private static final Object LOCK = new Object();
+
+    public static void main(String... args) throws InterruptedException {
+        sleepWaitInSyncronizedBlocks();
+    }
+
+    private static void sleepWaitInSyncronizedBlocks() throws InterruptedException {
+        Thread.sleep(1000); // called on the thread
+        System.out.println("Thread '" + Thread.currentThread().getName() + "' is woken after sleeping for 1 second");
+
+        synchronized (LOCK) {
+            LOCK.wait(1000); // called on the object, synchronization required
+            System.out.println("Object '" + LOCK + "' is woken after waiting for 1 second");
+        }
+    }
+    
+}