Add Singleton example to Design Patterns

dawand · Jan 2, 2021 · fd34d7b · fd34d7b
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diff --git a/Java/Advanced-Java/Advanced-Java.iml → Advanced-Java/Advanced-Java.iml b/Java/Advanced-Java/Advanced-Java.iml → Advanced-Java/Advanced-Java.iml
diff --git a/...rogramming/CompletableFutureExample.class → ...rogramming/CompletableFutureExample.class b/...rogramming/CompletableFutureExample.class → ...rogramming/CompletableFutureExample.class
diff --git a/...n/Advanced-Java/Callbacks/Callbacks.class → ...n/Advanced-Java/Callbacks/Callbacks.class b/...n/Advanced-Java/Callbacks/Callbacks.class → ...n/Advanced-Java/Callbacks/Callbacks.class
diff --git a/...nced-Java/Callbacks/Lambdas$Service.class → ...nced-Java/Callbacks/Lambdas$Service.class b/...nced-Java/Callbacks/Lambdas$Service.class → ...nced-Java/Callbacks/Lambdas$Service.class
diff --git a/...ion/Advanced-Java/Callbacks/Lambdas.class → ...ion/Advanced-Java/Callbacks/Lambdas.class b/...ion/Advanced-Java/Callbacks/Lambdas.class → ...ion/Advanced-Java/Callbacks/Lambdas.class
diff --git a/...ced-Java/CombinatorPattern/Customer.class → ...ced-Java/CombinatorPattern/Customer.class b/...ced-Java/CombinatorPattern/Customer.class → ...ced-Java/CombinatorPattern/Customer.class
diff --git a/...ttern/CustomerRegistrationValidator.class → ...ttern/CustomerRegistrationValidator.class b/...ttern/CustomerRegistrationValidator.class → ...ttern/CustomerRegistrationValidator.class
diff --git a/...torPattern/CustomerValidatorService.class → ...torPattern/CustomerValidatorService.class b/...torPattern/CustomerValidatorService.class → ...torPattern/CustomerValidatorService.class
diff --git a/...dvanced-Java/CombinatorPattern/Main.class → ...dvanced-Java/CombinatorPattern/Main.class b/...dvanced-Java/CombinatorPattern/Main.class → ...dvanced-Java/CombinatorPattern/Main.class
diff --git a/.../CombinatorPattern/ValidationResult.class → .../CombinatorPattern/ValidationResult.class b/.../CombinatorPattern/ValidationResult.class → .../CombinatorPattern/ValidationResult.class
diff --git a/...d-Java/Concurrency/ConditionExample.class → ...d-Java/Concurrency/ConditionExample.class b/...d-Java/Concurrency/ConditionExample.class → ...d-Java/Concurrency/ConditionExample.class
diff --git a/...Java/Concurrency/ThreadLocalExample.class → ...Java/Concurrency/ThreadLocalExample.class b/...Java/Concurrency/ThreadLocalExample.class → ...Java/Concurrency/ThreadLocalExample.class
diff --git a/...ava/Concurrency/ThreadSafeFormatter.class → ...ava/Concurrency/ThreadSafeFormatter.class b/...ava/Concurrency/ThreadSafeFormatter.class → ...ava/Concurrency/ThreadSafeFormatter.class
diff --git a/...rrency/VolatileOrAtomic$FlagChecker.class → ...rrency/VolatileOrAtomic$FlagChecker.class b/...rrency/VolatileOrAtomic$FlagChecker.class → ...rrency/VolatileOrAtomic$FlagChecker.class
diff --git a/...rrency/VolatileOrAtomic$FlagUpdater.class → ...rrency/VolatileOrAtomic$FlagUpdater.class b/...rrency/VolatileOrAtomic$FlagUpdater.class → ...rrency/VolatileOrAtomic$FlagUpdater.class
diff --git a/...d-Java/Concurrency/VolatileOrAtomic.class → ...d-Java/Concurrency/VolatileOrAtomic.class b/...d-Java/Concurrency/VolatileOrAtomic.class → ...d-Java/Concurrency/VolatileOrAtomic.class
diff --git a/...d-Java/DesignPatterns/TaxCalculator.class → ...d-Java/DesignPatterns/TaxCalculator.class b/...d-Java/DesignPatterns/TaxCalculator.class → ...d-Java/DesignPatterns/TaxCalculator.class
diff --git a/...va/DesignPatterns/TaxCalculator2019.class → ...va/DesignPatterns/TaxCalculator2019.class b/...va/DesignPatterns/TaxCalculator2019.class → ...va/DesignPatterns/TaxCalculator2019.class
diff --git a/...va/DesignPatterns/TaxCalculator2020.class → ...va/DesignPatterns/TaxCalculator2020.class b/...va/DesignPatterns/TaxCalculator2020.class → ...va/DesignPatterns/TaxCalculator2020.class
diff --git a/...n/Advanced-Java/DesignPatterns/User.class → ...n/Advanced-Java/DesignPatterns/User.class b/...n/Advanced-Java/DesignPatterns/User.class → ...n/Advanced-Java/DesignPatterns/User.class
diff --git a/...-Java/DesignPatterns/memento/Editor.class → ...-Java/DesignPatterns/memento/Editor.class b/...-Java/DesignPatterns/memento/Editor.class → ...-Java/DesignPatterns/memento/Editor.class
diff --git a/.../DesignPatterns/memento/EditorState.class → .../DesignPatterns/memento/EditorState.class b/.../DesignPatterns/memento/EditorState.class → .../DesignPatterns/memento/EditorState.class
diff --git a/...Java/DesignPatterns/memento/History.class → ...Java/DesignPatterns/memento/History.class b/...Java/DesignPatterns/memento/History.class → ...Java/DesignPatterns/memento/History.class
diff --git a/...ed-Java/DesignPatterns/memento/Main.class → ...ed-Java/DesignPatterns/memento/Main.class b/...ed-Java/DesignPatterns/memento/Main.class → ...ed-Java/DesignPatterns/memento/Main.class
diff --git a/...Java/DesignPatterns/state/BrushTool.class → ...Java/DesignPatterns/state/BrushTool.class b/...Java/DesignPatterns/state/BrushTool.class → ...Java/DesignPatterns/state/BrushTool.class
diff --git a/...ed-Java/DesignPatterns/state/Canvas.class → ...ed-Java/DesignPatterns/state/Canvas.class b/...ed-Java/DesignPatterns/state/Canvas.class → ...ed-Java/DesignPatterns/state/Canvas.class
diff --git a/...nced-Java/DesignPatterns/state/Main.class → ...nced-Java/DesignPatterns/state/Main.class b/...nced-Java/DesignPatterns/state/Main.class → ...nced-Java/DesignPatterns/state/Main.class
diff --git a/...Java/DesignPatterns/state/Selection.class → ...Java/DesignPatterns/state/Selection.class b/...Java/DesignPatterns/state/Selection.class → ...Java/DesignPatterns/state/Selection.class
diff --git a/...nced-Java/DesignPatterns/state/Tool.class → ...nced-Java/DesignPatterns/state/Tool.class b/...nced-Java/DesignPatterns/state/Tool.class → ...nced-Java/DesignPatterns/state/Tool.class
diff --git a/...-Java/DesignPatterns/state/ToolType.class → ...-Java/DesignPatterns/state/ToolType.class b/...-Java/DesignPatterns/state/ToolType.class → ...-Java/DesignPatterns/state/ToolType.class
diff --git a/...d-Java/FunctionalProgramming/Gender.class → ...d-Java/FunctionalProgramming/Gender.class b/...d-Java/FunctionalProgramming/Gender.class → ...d-Java/FunctionalProgramming/Gender.class
diff --git a/...ced-Java/FunctionalProgramming/Main.class → ...ced-Java/FunctionalProgramming/Main.class b/...ced-Java/FunctionalProgramming/Main.class → ...ced-Java/FunctionalProgramming/Main.class
diff --git a/...d-Java/FunctionalProgramming/Person.class → ...d-Java/FunctionalProgramming/Person.class b/...d-Java/FunctionalProgramming/Person.class → ...d-Java/FunctionalProgramming/Person.class
diff --git a/...ava/FunctionalProgramming/_Function.class → ...ava/FunctionalProgramming/_Function.class b/...ava/FunctionalProgramming/_Function.class → ...ava/FunctionalProgramming/_Function.class
diff --git a/...va/FunctionalProgramming/_Predicate.class → ...va/FunctionalProgramming/_Predicate.class b/...va/FunctionalProgramming/_Predicate.class → ...va/FunctionalProgramming/_Predicate.class
diff --git a/...ava/FunctionalProgramming/_Supplier.class → ...ava/FunctionalProgramming/_Supplier.class b/...ava/FunctionalProgramming/_Supplier.class → ...ava/FunctionalProgramming/_Supplier.class
diff --git a/...Java/META-INF/Advanced-Java.kotlin_module → ...Java/META-INF/Advanced-Java.kotlin_module b/...Java/META-INF/Advanced-Java.kotlin_module → ...Java/META-INF/Advanced-Java.kotlin_module
diff --git a/.../Advanced-Java/Optionals/_Optionals.class → .../Advanced-Java/Optionals/_Optionals.class b/.../Advanced-Java/Optionals/_Optionals.class → .../Advanced-Java/Optionals/_Optionals.class
diff --git a/.../Advanced-Java/csv_reader/CSVReader.class → .../Advanced-Java/csv_reader/CSVReader.class b/.../Advanced-Java/csv_reader/CSVReader.class → .../Advanced-Java/csv_reader/CSVReader.class
diff --git a/...duction/Advanced-Java/csv_reader/data.csv → ...duction/Advanced-Java/csv_reader/data.csv b/...duction/Advanced-Java/csv_reader/data.csv → ...duction/Advanced-Java/csv_reader/data.csv
diff --git a/...nced-Java/dsa_koffman_ch2/JUnitTest.class → ...nced-Java/dsa_koffman_ch2/JUnitTest.class b/...nced-Java/dsa_koffman_ch2/JUnitTest.class → ...nced-Java/dsa_koffman_ch2/JUnitTest.class
diff --git a/...ed-Java/dsa_koffman_ch2/OrderedList.class → ...ed-Java/dsa_koffman_ch2/OrderedList.class b/...ed-Java/dsa_koffman_ch2/OrderedList.class → ...ed-Java/dsa_koffman_ch2/OrderedList.class
diff --git a/...ava/dsa_koffman_ch2/TestOrderedList.class → ...ava/dsa_koffman_ch2/TestOrderedList.class b/...ava/dsa_koffman_ch2/TestOrderedList.class → ...ava/dsa_koffman_ch2/TestOrderedList.class
diff --git a/...n/Advanced-Java/interfaces/Employee.class → ...n/Advanced-Java/interfaces/Employee.class b/...n/Advanced-Java/interfaces/Employee.class → ...n/Advanced-Java/interfaces/Employee.class
diff --git a/...ion/Advanced-Java/interfaces/Person.class → ...ion/Advanced-Java/interfaces/Person.class b/...ion/Advanced-Java/interfaces/Person.class → ...ion/Advanced-Java/interfaces/Person.class
diff --git a/...vanced-Java/interfaces/TaxCollector.class → ...vanced-Java/interfaces/TaxCollector.class b/...vanced-Java/interfaces/TaxCollector.class → ...vanced-Java/interfaces/TaxCollector.class
diff --git a/...n/Advanced-Java/interfaces/TaxPayer.class → ...n/Advanced-Java/interfaces/TaxPayer.class b/...n/Advanced-Java/interfaces/TaxPayer.class → ...n/Advanced-Java/interfaces/TaxPayer.class
diff --git a/...java8_features/FunctionalInterfaces.class → ...java8_features/FunctionalInterfaces.class b/...java8_features/FunctionalInterfaces.class → ...java8_features/FunctionalInterfaces.class
diff --git a/...Java/java8_features/GreetingService.class → ...Java/java8_features/GreetingService.class b/...Java/java8_features/GreetingService.class → ...Java/java8_features/GreetingService.class
diff --git a/...Advanced-Java/java8_features/Lambda.class → ...Advanced-Java/java8_features/Lambda.class b/...Advanced-Java/java8_features/Lambda.class → ...Advanced-Java/java8_features/Lambda.class
diff --git a/...java8_features/LocalDateTimeExample.class → ...java8_features/LocalDateTimeExample.class b/...java8_features/LocalDateTimeExample.class → ...java8_features/LocalDateTimeExample.class
diff --git a/...d-Java/java8_features/MathOperation.class → ...d-Java/java8_features/MathOperation.class b/...d-Java/java8_features/MathOperation.class → ...d-Java/java8_features/MathOperation.class
diff --git a/...Java/java8_features/MethodReference.class → ...Java/java8_features/MethodReference.class b/...Java/java8_features/MethodReference.class → ...Java/java8_features/MethodReference.class
diff --git a/...Advanced-Java/java8_features/Stream.class → ...Advanced-Java/java8_features/Stream.class b/...Advanced-Java/java8_features/Stream.class → ...Advanced-Java/java8_features/Stream.class
diff --git a/...vanced-Java/java_gc/FinalizeExample.class → ...vanced-Java/java_gc/FinalizeExample.class b/...vanced-Java/java_gc/FinalizeExample.class → ...vanced-Java/java_gc/FinalizeExample.class
diff --git a/...uction/Advanced-Java/java_gc/Person.class → ...uction/Advanced-Java/java_gc/Person.class b/...uction/Advanced-Java/java_gc/Person.class → ...uction/Advanced-Java/java_gc/Person.class
diff --git a/...dvanced-Java/java_gc/PersonMetaData.class → ...dvanced-Java/java_gc/PersonMetaData.class b/...dvanced-Java/java_gc/PersonMetaData.class → ...dvanced-Java/java_gc/PersonMetaData.class
diff --git a/...ced-Java/java_gc/WeakHashMapExample.class → ...ced-Java/java_gc/WeakHashMapExample.class b/...ced-Java/java_gc/WeakHashMapExample.class → ...ced-Java/java_gc/WeakHashMapExample.class
diff --git a/...d-Java/java_gc/WeakReferenceExample.class → ...d-Java/java_gc/WeakReferenceExample.class b/...d-Java/java_gc/WeakReferenceExample.class → ...d-Java/java_gc/WeakReferenceExample.class
diff --git a/...Programming/CompletableFutureExample.java → ...Programming/CompletableFutureExample.java b/...Programming/CompletableFutureExample.java → ...Programming/CompletableFutureExample.java
diff --git a/...dvanced-Java/src/Callbacks/Callbacks.java → Advanced-Java/src/Callbacks/Callbacks.java b/...dvanced-Java/src/Callbacks/Callbacks.java → Advanced-Java/src/Callbacks/Callbacks.java
diff --git a/.../Advanced-Java/src/Callbacks/Lambdas.java → Advanced-Java/src/Callbacks/Lambdas.java b/.../Advanced-Java/src/Callbacks/Lambdas.java → Advanced-Java/src/Callbacks/Lambdas.java
diff --git a/...-Java/src/CombinatorPattern/Customer.java → ...-Java/src/CombinatorPattern/Customer.java b/...-Java/src/CombinatorPattern/Customer.java → ...-Java/src/CombinatorPattern/Customer.java
diff --git a/...attern/CustomerRegistrationValidator.java → ...attern/CustomerRegistrationValidator.java b/...attern/CustomerRegistrationValidator.java → ...attern/CustomerRegistrationValidator.java
diff --git a/...atorPattern/CustomerValidatorService.java → ...atorPattern/CustomerValidatorService.java b/...atorPattern/CustomerValidatorService.java → ...atorPattern/CustomerValidatorService.java
diff --git a/...nced-Java/src/CombinatorPattern/Main.java → ...nced-Java/src/CombinatorPattern/Main.java b/...nced-Java/src/CombinatorPattern/Main.java → ...nced-Java/src/CombinatorPattern/Main.java
diff --git a/...c/CombinatorPattern/ValidationResult.java → ...c/CombinatorPattern/ValidationResult.java b/...c/CombinatorPattern/ValidationResult.java → ...c/CombinatorPattern/ValidationResult.java
diff --git a/...ava/src/Concurrency/ConditionExample.java → ...ava/src/Concurrency/ConditionExample.java b/...ava/src/Concurrency/ConditionExample.java → ...ava/src/Concurrency/ConditionExample.java
diff --git a/...nced-Java/src/Concurrency/MyRunnable.java → ...nced-Java/src/Concurrency/MyRunnable.java b/...nced-Java/src/Concurrency/MyRunnable.java → ...nced-Java/src/Concurrency/MyRunnable.java
diff --git a/...-Java/src/Concurrency/MyRunnableMain.java → ...-Java/src/Concurrency/MyRunnableMain.java b/...-Java/src/Concurrency/MyRunnableMain.java → ...-Java/src/Concurrency/MyRunnableMain.java
diff --git a/...a/src/Concurrency/ThreadLocalExample.java → ...a/src/Concurrency/ThreadLocalExample.java b/...a/src/Concurrency/ThreadLocalExample.java → ...a/src/Concurrency/ThreadLocalExample.java
diff --git a/...ava/src/Concurrency/VolatileOrAtomic.java → ...ava/src/Concurrency/VolatileOrAtomic.java b/...ava/src/Concurrency/VolatileOrAtomic.java → ...ava/src/Concurrency/VolatileOrAtomic.java
diff --git a/...ava/src/DesignPatterns/TaxCalculator.java → ...ava/src/DesignPatterns/TaxCalculator.java b/...ava/src/DesignPatterns/TaxCalculator.java → ...ava/src/DesignPatterns/TaxCalculator.java
diff --git a/...src/DesignPatterns/TaxCalculator2019.java → ...src/DesignPatterns/TaxCalculator2019.java b/...src/DesignPatterns/TaxCalculator2019.java → ...src/DesignPatterns/TaxCalculator2019.java
diff --git a/...src/DesignPatterns/TaxCalculator2020.java → ...src/DesignPatterns/TaxCalculator2020.java b/...src/DesignPatterns/TaxCalculator2020.java → ...src/DesignPatterns/TaxCalculator2020.java
diff --git a/...dvanced-Java/src/DesignPatterns/User.java → Advanced-Java/src/DesignPatterns/User.java b/...dvanced-Java/src/DesignPatterns/User.java → Advanced-Java/src/DesignPatterns/User.java
diff --git a/...va/src/DesignPatterns/memento/Editor.java → ...va/src/DesignPatterns/memento/Editor.java b/...va/src/DesignPatterns/memento/Editor.java → ...va/src/DesignPatterns/memento/Editor.java
diff --git a/...c/DesignPatterns/memento/EditorState.java → ...c/DesignPatterns/memento/EditorState.java b/...c/DesignPatterns/memento/EditorState.java → ...c/DesignPatterns/memento/EditorState.java
diff --git a/...a/src/DesignPatterns/memento/History.java → ...a/src/DesignPatterns/memento/History.java b/...a/src/DesignPatterns/memento/History.java → ...a/src/DesignPatterns/memento/History.java
diff --git a/...Java/src/DesignPatterns/memento/Main.java → ...Java/src/DesignPatterns/memento/Main.java b/...Java/src/DesignPatterns/memento/Main.java → ...Java/src/DesignPatterns/memento/Main.java
diff --git a/...a/src/DesignPatterns/state/BrushTool.java → ...a/src/DesignPatterns/state/BrushTool.java b/...a/src/DesignPatterns/state/BrushTool.java → ...a/src/DesignPatterns/state/BrushTool.java
diff --git a/...Java/src/DesignPatterns/state/Canvas.java → ...Java/src/DesignPatterns/state/Canvas.java b/...Java/src/DesignPatterns/state/Canvas.java → ...Java/src/DesignPatterns/state/Canvas.java
diff --git a/...d-Java/src/DesignPatterns/state/Main.java → ...d-Java/src/DesignPatterns/state/Main.java b/...d-Java/src/DesignPatterns/state/Main.java → ...d-Java/src/DesignPatterns/state/Main.java
diff --git a/...a/src/DesignPatterns/state/Selection.java → ...a/src/DesignPatterns/state/Selection.java b/...a/src/DesignPatterns/state/Selection.java → ...a/src/DesignPatterns/state/Selection.java
diff --git a/...d-Java/src/DesignPatterns/state/Tool.java → ...d-Java/src/DesignPatterns/state/Tool.java b/...d-Java/src/DesignPatterns/state/Tool.java → ...d-Java/src/DesignPatterns/state/Tool.java
diff --git a/...va/src/DesignPatterns/state/ToolType.java → ...va/src/DesignPatterns/state/ToolType.java b/...va/src/DesignPatterns/state/ToolType.java → ...va/src/DesignPatterns/state/ToolType.java
diff --git a/...ava/src/FunctionalProgramming/Gender.java → ...ava/src/FunctionalProgramming/Gender.java b/...ava/src/FunctionalProgramming/Gender.java → ...ava/src/FunctionalProgramming/Gender.java
diff --git a/...-Java/src/FunctionalProgramming/Main.java → ...-Java/src/FunctionalProgramming/Main.java b/...-Java/src/FunctionalProgramming/Main.java → ...-Java/src/FunctionalProgramming/Main.java
diff --git a/...ava/src/FunctionalProgramming/Person.java → ...ava/src/FunctionalProgramming/Person.java b/...ava/src/FunctionalProgramming/Person.java → ...ava/src/FunctionalProgramming/Person.java
diff --git a/.../src/FunctionalProgramming/_Function.java → .../src/FunctionalProgramming/_Function.java b/.../src/FunctionalProgramming/_Function.java → .../src/FunctionalProgramming/_Function.java
diff --git a/...src/FunctionalProgramming/_Predicate.java → ...src/FunctionalProgramming/_Predicate.java b/...src/FunctionalProgramming/_Predicate.java → ...src/FunctionalProgramming/_Predicate.java
diff --git a/.../src/FunctionalProgramming/_Supplier.java → .../src/FunctionalProgramming/_Supplier.java b/.../src/FunctionalProgramming/_Supplier.java → .../src/FunctionalProgramming/_Supplier.java
diff --git a/...vanced-Java/src/Optionals/_Optionals.java → Advanced-Java/src/Optionals/_Optionals.java b/...vanced-Java/src/Optionals/_Optionals.java → Advanced-Java/src/Optionals/_Optionals.java
diff --git a/...vanced-Java/src/csv_reader/CSVReader.java → Advanced-Java/src/csv_reader/CSVReader.java b/...vanced-Java/src/csv_reader/CSVReader.java → Advanced-Java/src/csv_reader/CSVReader.java
diff --git a/Java/Advanced-Java/src/csv_reader/data.csv → Advanced-Java/src/csv_reader/data.csv b/Java/Advanced-Java/src/csv_reader/data.csv → Advanced-Java/src/csv_reader/data.csv
diff --git a/...d-Java/src/dsa_koffman_ch2/JUnitTest.java → ...d-Java/src/dsa_koffman_ch2/JUnitTest.java b/...d-Java/src/dsa_koffman_ch2/JUnitTest.java → ...d-Java/src/dsa_koffman_ch2/JUnitTest.java
diff --git a/...Java/src/dsa_koffman_ch2/OrderedList.java → ...Java/src/dsa_koffman_ch2/OrderedList.java b/...Java/src/dsa_koffman_ch2/OrderedList.java → ...Java/src/dsa_koffman_ch2/OrderedList.java
diff --git a/.../src/dsa_koffman_ch2/TestOrderedList.java → .../src/dsa_koffman_ch2/TestOrderedList.java b/.../src/dsa_koffman_ch2/TestOrderedList.java → .../src/dsa_koffman_ch2/TestOrderedList.java
diff --git a/...dvanced-Java/src/interfaces/Employee.java → Advanced-Java/src/interfaces/Employee.java b/...dvanced-Java/src/interfaces/Employee.java → Advanced-Java/src/interfaces/Employee.java
diff --git a/.../Advanced-Java/src/interfaces/Person.java → Advanced-Java/src/interfaces/Person.java b/.../Advanced-Java/src/interfaces/Person.java → Advanced-Java/src/interfaces/Person.java
diff --git a/...ced-Java/src/interfaces/TaxCollector.java → ...ced-Java/src/interfaces/TaxCollector.java b/...ced-Java/src/interfaces/TaxCollector.java → ...ced-Java/src/interfaces/TaxCollector.java
diff --git a/...dvanced-Java/src/interfaces/TaxPayer.java → Advanced-Java/src/interfaces/TaxPayer.java b/...dvanced-Java/src/interfaces/TaxPayer.java → Advanced-Java/src/interfaces/TaxPayer.java
diff --git a/.../java8_features/FunctionalInterfaces.java → .../java8_features/FunctionalInterfaces.java b/.../java8_features/FunctionalInterfaces.java → .../java8_features/FunctionalInterfaces.java
diff --git a/...anced-Java/src/java8_features/Lambda.java → Advanced-Java/src/java8_features/Lambda.java b/...anced-Java/src/java8_features/Lambda.java → Advanced-Java/src/java8_features/Lambda.java
diff --git a/.../java8_features/LocalDateTimeExample.java → .../java8_features/LocalDateTimeExample.java b/.../java8_features/LocalDateTimeExample.java → .../java8_features/LocalDateTimeExample.java
diff --git a/...a/src/java8_features/MethodReference.java → ...a/src/java8_features/MethodReference.java b/...a/src/java8_features/MethodReference.java → ...a/src/java8_features/MethodReference.java
diff --git a/...anced-Java/src/java8_features/Stream.java → Advanced-Java/src/java8_features/Stream.java b/...anced-Java/src/java8_features/Stream.java → Advanced-Java/src/java8_features/Stream.java
diff --git a/...ced-Java/src/java_gc/FinalizeExample.java → ...ced-Java/src/java_gc/FinalizeExample.java b/...ced-Java/src/java_gc/FinalizeExample.java → ...ced-Java/src/java_gc/FinalizeExample.java
diff --git a/...-Java/src/java_gc/WeakHashMapExample.java → ...-Java/src/java_gc/WeakHashMapExample.java b/...-Java/src/java_gc/WeakHashMapExample.java → ...-Java/src/java_gc/WeakHashMapExample.java
diff --git a/...ava/src/java_gc/WeakReferenceExample.java → ...ava/src/java_gc/WeakReferenceExample.java b/...ava/src/java_gc/WeakReferenceExample.java → ...ava/src/java_gc/WeakReferenceExample.java
diff --git a/Design-patterns/src/singleton/Captain.java b/Design-patterns/src/singleton/Captain.java
@@ -0,0 +1,21 @@
+package singleton;
+
+// final is to avoid having non-static nested classes subclassing Captain
+final class Captain {
+
+    private static Captain captain;
+
+    private Captain() {}
+
+    // synchronized is for multithreaded purpose
+    public static synchronized Captain getInstance() {
+        if (captain == null) { // lazy initialization
+            captain = new Captain();
+            System.out.println("A new captain is created :)");
+            return captain;
+        } else {
+            System.out.println("You already have a captain!");
+        }
+            return captain;
+    }
+}
diff --git a/Design-patterns/src/singleton/SingletonExample.java b/Design-patterns/src/singleton/SingletonExample.java
@@ -0,0 +1,13 @@
+package singleton;
+
+public class SingletonExample {
+    public static void main(String[] args) {
+        Captain captain1 = Captain.getInstance();
+        Captain captain2 = Captain.getInstance();
+
+        if (captain1 == captain2) {
+            System.out.println("Captain 1 and 2 are same instances");
+        }
+
+    }
+}
diff --git a/interview-preparation.iml b/interview-preparation.iml
@@ -4,6 +4,7 @@
     <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/problems" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/Design-patterns/src" isTestSource="false" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />