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Commit 070ada1

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GP-24 add CrazyLambdas, CrazyStreams and CrazyOptionals to functional-programming module
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‎6-0-functional-programming/pom.xml‎

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<maven.compiler.source>11</maven.compiler.source>
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</properties>
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<dependencies>
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<dependency>
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<groupId>com.bobocode</groupId>
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<artifactId>java-fundamentals-util</artifactId>
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<version>1.0-SNAPSHOT</version>
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</dependency>
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</dependencies>
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</project>
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package com.bobocode.lambdas;
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import com.bobocode.util.ExerciseNotCompletedException;
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import java.math.BigDecimal;
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import java.util.Map;
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import java.util.function.*;
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public class CrazyLambdas {
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/**
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* Returns {@link Supplier} that always supply "Hello"
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*
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* @return a string supplier
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*/
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public static Supplier<String> helloSupplier() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link Predicate} of string that checks if string is empty
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*
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* @return a string predicate
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*/
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public static Predicate<String> isEmptyPredicate() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Return a {@link Function} that accepts {@link String} and returns that string repeated n time, where n is passed
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* as function argument
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*
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* @return function that repeats Strings
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*/
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public static BiFunction<String, Integer, String> stringMultiplier() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link Function} that converts a {@link BigDecimal} number into a {@link String} that start with
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* a dollar sign and then gets a value
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*
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* @return function that converts adds dollar sign
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*/
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public static Function<BigDecimal, String> toDollarStringFunction() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Receives two parameter that represent a range and returns a {@link Predicate<String>} that verifies if string
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* length is in the specified range. E.g. min <= length < max
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*
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* @param min min length
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* @param max max length
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* @return a string predicate
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*/
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public static Predicate<String> lengthInRangePredicate(int min, int max) {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link Supplier} of random integers
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*
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* @return int supplier
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*/
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public static IntSupplier randomIntSupplier() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns an {@link IntUnaryOperator} that receives an int as a bound parameter, and returns a random int
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*
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* @return int operation
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*/
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public static IntUnaryOperator boundedRandomIntSupplier() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns {@link IntUnaryOperator} that calculates an integer square
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*
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* @return square operation
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*/
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public static IntUnaryOperator intSquareOperation() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link LongBinaryOperator} sum operation.
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*
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* @return binary sum operation
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*/
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public static LongBinaryOperator longSumOperation() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link ToIntFunction<String>} that converts string to integer.
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*
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* @return string to int converter
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*/
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public static ToIntFunction<String> stringToIntConverter() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Receives int parameter n, and returns a {@link Supplier} that supplies {@link IntUnaryOperator}
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* that is a function f(x) = n * x
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*
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* @param n a multiplier
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* @return a function supplier
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*/
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public static Supplier<IntUnaryOperator> nMultiplyFunctionSupplier(int n) {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link UnaryOperator} that accepts str to str function and returns the same function composed with trim
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*
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* @return function that composes functions with trim() function
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*/
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public static UnaryOperator<Function<String, String>> composeWithTrimFunction() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Receives a {@link Runnable} parameter, and returns a {@link Supplier<Thread>}. The thread will be started only
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* when you call supplier method {@link Supplier#get()}
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*
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* @param runnable the code you want to tun in new thread
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* @return a thread supplier
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*/
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public static Supplier<Thread> runningThreadSupplier(Runnable runnable) {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link Consumer} that accepts {@link Runnable} as a parameter and runs in in a new thread.
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*
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* @return a runnable consumer
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*/
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public static Consumer<Runnable> newThreadRunnableConsumer() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link Function} that accepts an instance of {@link Runnable} and returns a {@link Supplier} of a
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* started {@link Thread} that is created from a given {@link Runnable}
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*
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* @return a function that transforms runnable into a thread supplier
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*/
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public static Function<Runnable, Supplier<Thread>> runnableToThreadSupplierFunction() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link BiFunction} that has two parameters. First is {@link IntUnaryOperator} which is some integer function.
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* Second is {@link IntPredicate} which is some integer condition. And the third is {@link IntUnaryOperator} which is
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* a new composed function that uses provided predicate (second parameter of binary function) to verify its input
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* parameter. If predicate returns {@code true} it applies a provided integer function
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* (first parameter of binary function) and returns a result value, otherwise it returns an element itself.
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*
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* @return a binary function that receiver predicate and function and compose them to create a new function
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*/
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public static BiFunction<IntUnaryOperator, IntPredicate, IntUnaryOperator> functionToConditionalFunction() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns a {@link BiFunction} which first parameter is a {@link Map} where key is a function name, and value is some
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* {@link IntUnaryOperator}, and second parameter is a {@link String} which is a function name. If the map contains a
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* function by a given name then it is returned by high order function otherwise an identity() is returned.
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*
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* @return a high-order function that fetches a function from a function map by a given name or returns identity()
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*/
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public static BiFunction<Map<String, IntUnaryOperator>, String, IntUnaryOperator> functionLoader() {
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throw new ExerciseNotCompletedException();
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}
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/**
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* Returns {@link Supplier} of {@link Supplier} of {@link Supplier} of {@link String} "WELL DONE".
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*
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* @return a supplier instance
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*/
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public static Supplier<Supplier<Supplier<String>>> trickyWellDoneSupplier() {
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throw new ExerciseNotCompletedException();
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}
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}
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# <img src="https://raw.githubusercontent.com/bobocode-projects/resources/master/image/logo_transparent_background.png" height=50/>Crazy lambda exercise :muscle:
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Improve your lambda skills
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### Task
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`CrazyLambdas` class consists of static methods that return various functions, operations and predicates.
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Your job is to implement the *todo* section of that class using **Lambda expressions** and **method reference**.
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To verify your implementation, run `CrazyLambdasTest.java`
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### Pre-conditions :heavy_exclamation_mark:
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You're supposed to be familiar with Java 8
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### How to start :question:
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* Just clone the repository and start implementing the **todo** section, verify your changes by running tests
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* If you don't have enough knowledge about this domain, check out the [links below](#related-materials-information_source)
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* Don't worry if you got stuck, checkout the **exercise/completed** branch and see the final implementation
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### Related materials :information_source:
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* [Lambda tutorial](https://github.com/bobocode-projects/java-8-tutorial/tree/master/lambdas) <img src="https://raw.githubusercontent.com/bobocode-projects/resources/master/image/logo_transparent_background.png" height=20/>
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* [State of lambda (JSR 335)](http://htmlpreview.github.io/?https://github.com/bobocode-projects/resources/blob/master/java8/lambda/sotl.html)
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package com.bobocode.optionals;
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public class AccountNotFoundException extends RuntimeException {
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public AccountNotFoundException(String message) {
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super(message);
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}
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}
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package com.bobocode.optionals;
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import com.bobocode.model.Account;
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import java.util.Optional;
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@FunctionalInterface
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public interface AccountProvider {
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Optional<Account> getAccount();
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}
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package com.bobocode.optionals;
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import com.bobocode.model.Account;
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@FunctionalInterface
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public interface AccountService {
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void processAccount(Account account);
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default void processWithNoAccount(){
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/* No operation */
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}
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}

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