Completed Functional Programming Exercise

1-0-java-basics/1-3-0-hello-generics/src/main/java/com/bobocode/basics/Box.java

@@ -7,18 +7,18 @@
  * <p>
  * todo: refactor this class so it uses generic type "T" and run {@link com.bobocode.basics.BoxTest} to verify it
  */
-public class Box {
-    private Object value;
+public class Box<T> {
+    private T value;
 
-    public Box(Object value) {
+    public Box(T value) {
         this.value = value;
     }
 
-    public Object getValue() {
+    public T getValue() {
         return value;
     }
 
-    public void setValue(Object value) {
+    public void setValue(T value) {
         this.value = value;
     }
 }

5-0-functional-programming/5-0-1-lambda-functions-map/src/main/java/com/bobocode/fp/Functions.java

@@ -28,7 +28,12 @@ private Functions() {
     public static FunctionMap<Integer, Integer> intFunctionMap() {
         FunctionMap<Integer, Integer> intFunctionMap = new FunctionMap<>();
 
-        // todo: according to the javadoc add functions using lambda expression
+        intFunctionMap.addFunction("abs", Math::abs);
+        intFunctionMap.addFunction("sgn", x -> Integer.compare(x,0));
+        intFunctionMap.addFunction("increment", x -> x + 1);
+        intFunctionMap.addFunction("decrement", x -> x-1);
+        intFunctionMap.addFunction("square", x -> x*x);
+
 
         return intFunctionMap;
     }

5-0-functional-programming/5-0-2-stream-sum-of-squares/src/main/java/com/bobocode/fp/SumOfSquares.java

@@ -2,6 +2,9 @@
 
 import com.bobocode.fp.exception.InvalidRangeException;
 
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
 /**
  * This class allow to calculate a sum of squares of integer number in a certain range. It was implemented using
  * OO approach. Your job is to refactor it using functional approach. E.g. avoid using mutable variables
@@ -25,11 +28,8 @@ static int calculateSumOfSquaresInRange(int startInclusive, int endInclusive) {
             throw new InvalidRangeException();
         }
 
-        // todo: refactor using functional approach – instead of using for loop, use IntStream.rangeClose()
-        int sumOfSquares = 0;
-        for (int i = startInclusive; i <= endInclusive; i++) {
-            sumOfSquares += i * i;
-        }
-        return sumOfSquares;
+        return IntStream.rangeClosed(startInclusive,endInclusive)
+                .map(i -> i * i)
+                .sum();
     }
 }

5-0-functional-programming/5-1-1-crazy-lambdas/src/main/java/com/bobocode/fp/CrazyLambdas.java

@@ -5,7 +5,10 @@
 import java.math.BigDecimal;
 import java.util.Comparator;
 import java.util.Map;
+import java.util.Random;
 import java.util.function.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * {@link CrazyLambdas} is an exercise class. Each method returns a functional interface and it should be implemented
@@ -20,14 +23,14 @@
  * @author Taras Boychuk
  */
 public class CrazyLambdas {
-
+     private static Random random = new Random();
     /**
      * Returns {@link Supplier} that always supply "Hello"
      *
      * @return a string supplier
      */
     public static Supplier<String> helloSupplier() {
-        throw new ExerciseNotCompletedException();
+        return () -> "Hello";
     }
 
     /**
@@ -36,7 +39,8 @@ public static Supplier<String> helloSupplier() {
      * @return a string predicate
      */
     public static Predicate<String> isEmptyPredicate() {
-        throw new ExerciseNotCompletedException();
+
+        return String::isEmpty;
     }
 
     /**
@@ -46,7 +50,9 @@ public static Predicate<String> isEmptyPredicate() {
      * @return function that repeats Strings
      */
     public static BiFunction<String, Integer, String> stringMultiplier() {
-        throw new ExerciseNotCompletedException();
+        return (str,inter)-> Stream.iterate(str, x->x)
+                .limit(inter)
+                .collect(Collectors.joining(""));
     }
 
     /**
@@ -56,7 +62,7 @@ public static BiFunction<String, Integer, String> stringMultiplier() {
      * @return function that converts adds dollar sign
      */
     public static Function<BigDecimal, String> toDollarStringFunction() {
-        throw new ExerciseNotCompletedException();
+        return dec-> "$" + dec.toString();
     }
 
     /**
@@ -68,7 +74,7 @@ public static Function<BigDecimal, String> toDollarStringFunction() {
      * @return a string predicate
      */
     public static Predicate<String> lengthInRangePredicate(int min, int max) {
-        throw new ExerciseNotCompletedException();
+        return (s) ->  min <= s.length() && s.length()< max  ;
     }
 
     /**
@@ -77,7 +83,7 @@ public static Predicate<String> lengthInRangePredicate(int min, int max) {
      * @return int supplier
      */
     public static IntSupplier randomIntSupplier() {
-        throw new ExerciseNotCompletedException();
+        return random::nextInt;
     }
 
 
@@ -87,7 +93,7 @@ public static IntSupplier randomIntSupplier() {
      * @return int operation
      */
     public static IntUnaryOperator boundedRandomIntSupplier() {
-        throw new ExerciseNotCompletedException();
+        return inter -> random.nextInt(inter);
     }
 
     /**
@@ -96,7 +102,7 @@ public static IntUnaryOperator boundedRandomIntSupplier() {
      * @return square operation
      */
     public static IntUnaryOperator intSquareOperation() {
-        throw new ExerciseNotCompletedException();
+        return inter -> inter * inter;
     }
 
     /**
@@ -105,7 +111,7 @@ public static IntUnaryOperator intSquareOperation() {
      * @return binary sum operation
      */
     public static LongBinaryOperator longSumOperation() {
-        throw new ExerciseNotCompletedException();
+        return Long::sum;
     }
 
     /**
@@ -114,7 +120,7 @@ public static LongBinaryOperator longSumOperation() {
      * @return string to int converter
      */
     public static ToIntFunction<String> stringToIntConverter() {
-        throw new ExerciseNotCompletedException();
+        return Integer::parseInt;
     }
 
     /**
@@ -125,7 +131,7 @@ public static ToIntFunction<String> stringToIntConverter() {
      * @return a function supplier
      */
     public static Supplier<IntUnaryOperator> nMultiplyFunctionSupplier(int n) {
-        throw new ExerciseNotCompletedException();
+        return ()-> x-> n * x;
     }
 
     /**
@@ -134,7 +140,7 @@ public static Supplier<IntUnaryOperator> nMultiplyFunctionSupplier(int n) {
      * @return function that composes functions with trim() function
      */
     public static UnaryOperator<Function<String, String>> composeWithTrimFunction() {
-        throw new ExerciseNotCompletedException();
+        return strFunction -> strFunction.compose(String::trim);
     }
 
     /**
@@ -145,7 +151,11 @@ public static UnaryOperator<Function<String, String>> composeWithTrimFunction()
      * @return a thread supplier
      */
     public static Supplier<Thread> runningThreadSupplier(Runnable runnable) {
-        throw new ExerciseNotCompletedException();
+        return () -> {
+            Thread t = new Thread(runnable);
+            t.start();
+            return t;
+        };
     }
 
     /**
@@ -154,7 +164,7 @@ public static Supplier<Thread> runningThreadSupplier(Runnable runnable) {
      * @return a runnable consumer
      */
     public static Consumer<Runnable> newThreadRunnableConsumer() {
-        throw new ExerciseNotCompletedException();
+        return runnable -> new Thread(runnable).start();
     }
 
     /**
@@ -164,7 +174,11 @@ public static Consumer<Runnable> newThreadRunnableConsumer() {
      * @return a function that transforms runnable into a thread supplier
      */
     public static Function<Runnable, Supplier<Thread>> runnableToThreadSupplierFunction() {
-        throw new ExerciseNotCompletedException();
+        return runnable -> () -> {
+            Thread t = new Thread(runnable);
+            t.start();
+            return t;
+        };
     }
 
     /**
@@ -177,7 +191,7 @@ public static Function<Runnable, Supplier<Thread>> runnableToThreadSupplierFunct
      * @return a binary function that receiver predicate and function and compose them to create a new function
      */
     public static BiFunction<IntUnaryOperator, IntPredicate, IntUnaryOperator> functionToConditionalFunction() {
-        throw new ExerciseNotCompletedException();
+        return (intFunction, condition) -> x -> condition.test(x) ? intFunction.applyAsInt(x) : x;
     }
 
     /**
@@ -188,7 +202,7 @@ public static BiFunction<IntUnaryOperator, IntPredicate, IntUnaryOperator> funct
      * @return a high-order function that fetches a function from a function map by a given name or returns identity()
      */
     public static BiFunction<Map<String, IntUnaryOperator>, String, IntUnaryOperator> functionLoader() {
-        throw new ExerciseNotCompletedException();
+        return (functionMap, functionName) -> functionMap.getOrDefault(functionName, IntUnaryOperator.identity());
     }
 
     /**
@@ -206,7 +220,7 @@ public static BiFunction<Map<String, IntUnaryOperator>, String, IntUnaryOperator
      * @return a comparator instance
      */
     public static <T, U extends Comparable<? super U>> Comparator<T> comparing(Function<? super T, ? extends U> mapper) {
-        throw new ExerciseNotCompletedException();
+        return (o1, o2) -> mapper.apply(o1).compareTo(mapper.apply(o2));
     }
 
     /**
@@ -226,7 +240,13 @@ public static <T, U extends Comparable<? super U>> Comparator<T> comparing(Funct
      */
     public static <T, U extends Comparable<? super U>> Comparator<T> thenComparing(
             Comparator<? super T> comparator, Function<? super T, ? extends U> mapper) {
-        throw new ExerciseNotCompletedException();
+        return (o1, o2) -> {
+            var initialResult = comparator.compare(o1, o2);
+            if (initialResult != 0) {
+                return initialResult;
+            }
+            return mapper.apply(o1).compareTo(mapper.apply(o2));
+        };
     }
 
     /**
@@ -235,7 +255,7 @@ public static <T, U extends Comparable<? super U>> Comparator<T> thenComparing(
      * @return a supplier instance
      */
     public static Supplier<Supplier<Supplier<String>>> trickyWellDoneSupplier() {
-        throw new ExerciseNotCompletedException();
+        return () -> () -> () -> "WELL DONE!";
     }
 }