diff --git a/tls/src/main/java/com/iluwatar/tls/App.java b/tls/src/main/java/com/iluwatar/tls/App.java
new file mode 100644
index 000000000..80e87042c
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/App.java
@@ -0,0 +1,146 @@
+/**
+ * The MIT License
+ * Copyright (c) 2016 Thomas Bauer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.tls;
+
+import java.util.Calendar;
+import java.util.Date;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+/**
+ * ThreadLocal pattern
+ *
+ * This App shows how to create an isolated space per each thread. In this
+ * example the usage of SimpleDateFormat is made to be thread-safe. This is an
+ * example of the ThreadLocal pattern.
+ *
+ * By applying the ThreadLocal pattern you can keep track of application
+ * instances or locale settings throughout the handling of a request. The
+ * ThreadLocal class works like a static variable, with the exception that it is
+ * only bound to the current thread! This allows us to use static variables in a
+ * thread-safe way.
+ *
+ * In Java, thread-local variables are implemented by the ThreadLocal class
+ * object. ThreadLocal holds a variable of type T, which is accessible via get/set
+ * methods.
+ *
+ * SimpleDateFormat is one of the basic Java classes and is not thread-safe. If
+ * you do not isolate the instance of SimpleDateFormat per each thread then
+ * problems arise.
+ *
+ * App converts the String date value 15/12/2015 to the Date format using the
+ * Java class SimpleDateFormat. It does this 20 times using 4 threads, each doing
+ * it 5 times. With the usage of as ThreadLocal in DateFormatCallable everything
+ * runs well. But if you comment out the ThreadLocal variant (marked with "//TLTL")
+ * and comment in the non ThreadLocal variant (marked with "//NTLNTL") you can
+ * see what will happen without the ThreadLocal. Most likely you will get incorrect
+ * date values and / or exceptions.
+ *
+ * This example clearly show what will happen when using non thread-safe classes
+ * in a thread. In real life this may happen one in of 1.000 or 10.000 conversions
+ * and those are really hard to find errors.
+ *
+ * @author Thomas Bauer, 2017
+ */
+public class App {
+ /**
+ * Program entry point
+ *
+ * @param args
+ * command line args
+ */
+ public static void main(String[] args) {
+ int counterDateValues = 0;
+ int counterExceptions = 0;
+
+ // Create a callable
+ DateFormatCallable callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
+ // start 4 threads, each using the same Callable instance
+ ExecutorService executor = Executors.newCachedThreadPool();
+
+ Future futureResult1 = executor.submit(callableDf);
+ Future futureResult2 = executor.submit(callableDf);
+ Future futureResult3 = executor.submit(callableDf);
+ Future futureResult4 = executor.submit(callableDf);
+ try {
+ Result[] result = new Result[4];
+ result[0] = futureResult1.get();
+ result[1] = futureResult2.get();
+ result[2] = futureResult3.get();
+ result[3] = futureResult4.get();
+
+ // Print results of thread executions (converted dates and raised exceptions)
+ // and count them
+ for (int i = 0; i < result.length; i++) {
+ counterDateValues = counterDateValues + printAndCountDates(result[i]);
+ counterExceptions = counterExceptions + printAndCountExceptions(result[i]);
+ }
+
+ // a correct run should deliver 20 times 15.12.2015
+ // and a correct run shouldn't deliver any exception
+ System.out.println("The List dateList contains " + counterDateValues + " date values");
+ System.out.println("The List exceptionList contains " + counterExceptions + " exceptions");
+
+ } catch (Exception e) {
+ // no action here
+ }
+ executor.shutdown();
+ }
+
+ /**
+ * Print result (date values) of a thread execution and count dates
+ *
+ * @param res contains results of a thread execution
+ */
+ private static int printAndCountDates(Result res) {
+ // a correct run should deliver 5 times 15.12.2015 per each thread
+ int counter = 0;
+ for (Date dt : res.getDateList()) {
+ counter++;
+ Calendar cal = Calendar.getInstance();
+ cal.setTime(dt);
+ // Formatted output of the date value: DD.MM.YYYY
+ System.out.println(
+ cal.get(Calendar.DAY_OF_MONTH) + "." + cal.get(Calendar.MONTH) + "." + +cal.get(Calendar.YEAR));
+ }
+ return counter;
+ }
+
+ /**
+ * Print result (exceptions) of a thread execution and count exceptions
+ *
+ * @param res contains results of a thread execution
+ * @return number of dates
+ */
+ private static int printAndCountExceptions(Result res) {
+ // a correct run shouldn't deliver any exception
+ int counter = 0;
+ for (String ex : res.getExceptionList()) {
+ counter++;
+ System.out.println(ex);
+ }
+ return counter;
+ }
+}
diff --git a/tls/src/main/java/com/iluwatar/tls/DateFormatCallable.java b/tls/src/main/java/com/iluwatar/tls/DateFormatCallable.java
new file mode 100644
index 000000000..a28e24d4e
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/DateFormatCallable.java
@@ -0,0 +1,98 @@
+/**
+ * The MIT License
+ * Copyright (c) 2016 Thomas Bauer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.tls;
+
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.concurrent.Callable;
+
+/**
+ * DateFormatCallable converts string dates to a date format using
+ * SimpleDateFormat. The date format and the date value will be passed to the
+ * Callable by the constructor. The constructor creates a instance of
+ * SimpleDateFormat and stores it in a ThreadLocal class variable. For the
+ * complete description of the example see {@link App}
+ *
+ * You can comment out the code marked with //TLTL and comment in the
+ * code marked //NTLNTL. Then you can see what will happen if you do not
+ * use the ThreadLocal. For details see the description of {@link App}
+ *
+ * @author Thomas Bauer, 2017
+ */
+public class DateFormatCallable implements Callable {
+ // class variables (members)
+ private ThreadLocal df; //TLTL
+ // private DateFormat df; //NTLNTL
+
+ private String dateValue; // for dateValue Thread Local not needed
+
+
+ /**
+ * The date format and the date value are passed to the constructor
+ *
+ * @param inDateFormat
+ * string date format string, e.g. "dd/MM/yyyy"
+ * @param inDateValue
+ * string date value, e.g. "21/06/2016"
+ */
+ public DateFormatCallable(String inDateFormat, String inDateValue) {
+ final String idf = inDateFormat; //TLTL
+ this.df = new ThreadLocal() { //TLTL
+ @Override //TLTL
+ protected DateFormat initialValue() { //TLTL
+ return new SimpleDateFormat(idf); //TLTL
+ } //TLTL
+ }; //TLTL
+ // this.df = new SimpleDateFormat(inDateFormat); //NTLNTL
+ this.dateValue = inDateValue;
+ }
+
+ /**
+ * @see java.util.concurrent.Callable#call()
+ */
+ @Override
+ public Result call() {
+ System.out.println(Thread.currentThread() + " started executing...");
+ Result result = new Result();
+
+ // Convert date value to date 5 times
+ for (int i = 1; i <= 5; i++) {
+ try {
+ // this is the statement where it is important to have the
+ // instance of SimpleDateFormat locally
+ // Create the date value and store it in dateList
+ result.getDateList().add(this.df.get().parse(this.dateValue)); //TLTL
+// result.getDateList().add(this.df.parse(this.dateValue)); //NTLNTL
+ } catch (Exception e) {
+ // write the Exception to a list and continue work
+ result.getExceptionList().add(e.getClass() + ": " + e.getMessage());
+ }
+
+ }
+
+ System.out.println(Thread.currentThread() + " finished processing part of the thread");
+
+ return result;
+ }
+}
diff --git a/tls/src/main/java/com/iluwatar/tls/Result.java b/tls/src/main/java/com/iluwatar/tls/Result.java
new file mode 100644
index 000000000..951a02a2f
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/Result.java
@@ -0,0 +1,40 @@
+/*
+ * Fiducia IT AG, All rights reserved. Use is subject to license terms.
+ */
+
+package com.iluwatar.tls;
+
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+
+/**
+ * Result object that will be returned by the Callable {@link DateFormatCallable}
+ * used in {@link App}
+ *
+ * @author Thomas Bauer, 2017
+ */
+public class Result {
+ // A list to collect the date values created in one thread
+ private List dateList = new ArrayList();
+
+ // A list to collect Exceptions thrown in one threads (should be none in
+ // this example)
+ private List exceptionList = new ArrayList();
+
+ /**
+ *
+ * @return List of date values collected within an thread execution
+ */
+ public List getDateList() {
+ return dateList;
+ }
+
+ /**
+ *
+ * @return List of exceptions thrown within an thread execution
+ */
+ public List getExceptionList() {
+ return exceptionList;
+ }
+}