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..b16aa1fc6
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/App.java
@@ -0,0 +1,108 @@
+/**
+ * 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.ArrayList;
+import java.util.Calendar;
+import java.util.Collections;
+import java.util.Date;
+import java.util.List;
+
+/**
+ * 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 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. These problems are described with the example {@link AppUgly}
+ *
+ */
+public class App {
+ // A list to collect the date values created in the the threads
+ static List dateList = Collections.synchronizedList(new ArrayList());
+
+ // A list to collect Exceptions thrown in the threads (should be none in
+ // this example)
+ static List exceptionList = Collections.synchronizedList(new ArrayList());
+
+ /**
+ * Program entry point
+ *
+ * @param args
+ * command line args
+ */
+ public static void main(String[] args) {
+ int counterDateValues = 0;
+ int counterExceptions = 0;
+
+ // Create a runnable
+ DateFormatRunnable runnableDf = new DateFormatRunnable("dd/MM/yyyy", "15/12/2015");
+ // start 4 threads, each using the same Runnable instance
+ Thread t1 = new Thread(runnableDf);
+ Thread t2 = new Thread(runnableDf);
+ Thread t3 = new Thread(runnableDf);
+ Thread t4 = new Thread(runnableDf);
+ t1.start();
+ t2.start();
+ t3.start();
+ t4.start();
+ try {
+ t1.join();
+ t2.join();
+ t3.join();
+ t4.join();
+ } catch (InterruptedException e) {
+ // Action not coded here
+ }
+ for (Date dt : dateList) {
+ // a correct run should deliver 20 times 15.12.2015
+ counterDateValues++;
+ 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));
+ }
+ for (String ex : exceptionList) {
+ // a correct run shouldn't deliver any exception
+ counterExceptions++;
+ System.out.println(ex);
+ }
+ System.out.println("The List dateList contains " + counterDateValues + " date values");
+ System.out.println("The List exceptionList contains " + counterExceptions + " exceptions");
+ }
+}
diff --git a/tls/src/main/java/com/iluwatar/tls/AppUgly.java b/tls/src/main/java/com/iluwatar/tls/AppUgly.java
new file mode 100644
index 000000000..7025d42b7
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/AppUgly.java
@@ -0,0 +1,112 @@
+/**
+ * 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.ArrayList;
+import java.util.Calendar;
+import java.util.Collections;
+import java.util.Date;
+import java.util.List;
+
+/**
+ *
+ * This App shows an example for problems with global thread variables. A global
+ * thread variable is a variable defined as class variable of a
+ * XyzRunnable-Class. In this example in the class
+ * {@link DateFormatUglyRunnable}
+ *
+ * Example use case: A well known problem with threads are non thread-safe Java
+ * classes. One example is the class SimpleDateFormat.
+ *
+ * In the example an instance of SimpleDateFormat is created in the constructor
+ * of the Runnable. The constructor initializes a class variable with the
+ * instance. The Runnable only does convert a string date to a date format using
+ * the instance of SimpleDateFormat. It does this 5 times.
+ *
+ * In the example 4 threads are started to do the same. If you are lucky
+ * everything works well. But if you try more often you will happen to see
+ * Exceptions. And these Exceptions arise on arbitrary points of the run.
+ *
+ * The reason for this exceptions is: The threads try to use internal instance
+ * variables of the SimpleDateFormat instance at the same time (the date is
+ * stored internal as member variable during parsing and may be overwritten by
+ * another thread during a parse is still running)
+ *
+ * And even without Exceptions the run may not deliver the correct results.
+ * All date values should be the same after the run. Check it
+ *
+ */
+public class AppUgly {
+ // A list to collect the date values created in the the threads
+ static List dateList = Collections.synchronizedList(new ArrayList());
+ // A list to collect Exceptions thrown in the threads
+ static List exceptionList = Collections.synchronizedList(new ArrayList());
+
+ /**
+ * Program entry point
+ *
+ * @param args
+ * command line args
+ */
+ public static void main(String[] args) {
+ int counterDateValues = 0;
+ int counterExceptions = 0;
+
+ // Prepare the Runnable
+ DateFormatUglyRunnable runnableDf = new DateFormatUglyRunnable("dd/MM/yyyy", "15/12/2015");
+
+ // 4 threads using the same Runnable
+ Thread t1 = new Thread(runnableDf);
+ Thread t2 = new Thread(runnableDf);
+ Thread t3 = new Thread(runnableDf);
+ Thread t4 = new Thread(runnableDf);
+ t1.start();
+ t2.start();
+ t3.start();
+ t4.start();
+ try {
+ t1.join();
+ t2.join();
+ t3.join();
+ t4.join();
+ } catch (InterruptedException e) {
+ // Action not coded here
+ }
+ for (Date dt : dateList) {
+ // a correct run should deliver 20 times 15.12.2015
+ counterDateValues++;
+ 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));
+ }
+ for (String ex : exceptionList) {
+ // a correct run shouldn't deliver any exception
+ counterExceptions++;
+ System.out.println(ex);
+ }
+ System.out.println("The List dateList contains " + counterDateValues + " date values");
+ System.out.println("The List exceptionList contains " + counterExceptions + " exceptions");
+ }
+}
diff --git a/tls/src/main/java/com/iluwatar/tls/DateFormatRunnable.java b/tls/src/main/java/com/iluwatar/tls/DateFormatRunnable.java
new file mode 100644
index 000000000..d2009d21b
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/DateFormatRunnable.java
@@ -0,0 +1,84 @@
+/**
+ * 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;
+
+/**
+ * DateFormatRunnable converts string dates to a date format using
+ * SimpleDateFormat The date format and the date value will be passed to the
+ * Runnable 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}
+ *
+ */
+public class DateFormatRunnable implements Runnable {
+ // class variables (members)
+ private ThreadLocal df;
+ private String dateValue; // for date Value 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 DateFormatRunnable(String inDateFormat, String inDateValue) {
+ final String idf = inDateFormat;
+ this.df = new ThreadLocal() {
+ @Override
+ protected DateFormat initialValue() {
+ return new SimpleDateFormat(idf);
+ }
+ };
+ this.dateValue = inDateValue;
+ }
+
+ /**
+ * @see java.lang.Runnable#run()
+ */
+ @Override
+ public void run() {
+ System.out.println(Thread.currentThread() + " started executing...");
+
+ // 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
+ App.dateList.add(this.df.get().parse(this.dateValue));
+ } catch (Exception e) {
+ // write the Exception to a list and continue work
+ App.exceptionList.add(e.getClass() + ": " + e.getMessage());
+ }
+
+ }
+
+ System.out.println(Thread.currentThread() + " finished executing");
+ }
+}
diff --git a/tls/src/main/java/com/iluwatar/tls/DateFormatUglyRunnable.java b/tls/src/main/java/com/iluwatar/tls/DateFormatUglyRunnable.java
new file mode 100644
index 000000000..ca883a913
--- /dev/null
+++ b/tls/src/main/java/com/iluwatar/tls/DateFormatUglyRunnable.java
@@ -0,0 +1,76 @@
+/**
+ * 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;
+
+/**
+ * DateFormatUglyRunnable converts string dates to a date format using
+ * SimpleDateFormat. The date value and the date format will be passed to the
+ * Runnable by the constructor. The constructor creates an instance of
+ * SimpleDateFormat and stores it in a class variable. For the complete
+ * description of the example see {@link AppUgly}
+ *
+ */
+public class DateFormatUglyRunnable implements Runnable {
+ // class variables (members)
+ private DateFormat df;
+ private String dateValue;
+
+ /**
+ * 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 DateFormatUglyRunnable(String inDateFormat, String inDateValue) {
+ this.df = new SimpleDateFormat(inDateFormat);
+ this.dateValue = inDateValue;
+ }
+
+ /**
+ * @see java.lang.Runnable#run()
+ */
+ @Override
+ public void run() {
+ System.out.println(Thread.currentThread() + " started executing...");
+
+ // Convert date value to date 5 times
+ for (int i = 1; i <= 5; i++) {
+ try {
+ // Create the date value and store it in dateList
+ AppUgly.dateList.add(this.df.parse(this.dateValue));
+ } catch (Exception e) {
+ // write the Exception to a list and continue work
+ AppUgly.exceptionList.add(e.getClass() + ": " + e.getMessage());
+ }
+
+ }
+
+ System.out.println(Thread.currentThread() + " finished executing");
+ }
+}