[W6D4] (ArndtED) Adds classes

testproject/src/main/java/com/nisum/ImprovedRandomSpliterator.java

+package com.nisum;
+
+//all credit to https://stackoverflow.com/users/2229438/grzegorz-piwowarek
+//https://stackoverflow.com/questions/45981964/how-to-get-a-random-element-from-a-list-with-stream-api/45982130
+
+import java.util.List;
+import java.util.Random;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class ImprovedRandomSpliterator<T> implements Spliterator<T> {
+
+    private final Random random;
+    private final T[] source;
+    private int size;
+
+    ImprovedRandomSpliterator(List<T> source, Supplier<? extends Random> random) {
+        if (source.isEmpty()) {
+            throw new IllegalArgumentException("RandomSpliterator can't be initialized with an empty collection");
+        }
+        this.source = (T[]) source.toArray();
+        this.random = random.get();
+        this.size = this.source.length;
+    }
+
+    @Override
+    public boolean tryAdvance(Consumer<? super T> action) {
+        if (size > 0) {
+            int nextIdx = random.nextInt(size);
+            int lastIdx = size - 1;
+
+            action.accept(source[nextIdx]);
+            source[nextIdx] = source[lastIdx];
+            source[lastIdx] = null; // let object be GCed
+            size--;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    @Override
+    public Spliterator<T> trySplit() {
+        return null;
+    }
+
+    @Override
+    public long estimateSize() {
+        return source.length;
+    }
+
+    @Override
+    public int characteristics() {
+        return SIZED;
+    }
+}
+
+

testproject/src/main/java/com/nisum/WhoIsTheBest.java

+package com.nisum;
+
+import java.util.*;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import static java.util.stream.Collectors.toCollection;
+
+
+
+public class WhoIsTheBest {
+
+    private List<String> theGreats;
+    private List<String> theNotSoGreats;
+    
+    public WhoIsTheBest(){
+        this.theGreats = Arrays.asList("Alex P", "Alex S", "Ben", "Chef", "Chris", "Darrick",
+                "Deep", "Joe", "John", "Julius", "Kevin", "Khai", "Kyle",
+                "Nikitha", "Philippe", "Shanelle", "Sumaiyya", "Vishal");
+        this.theNotSoGreats = Arrays.asList("Eric");
+    }
+
+    public List<String> getTheGreats() {
+        return theGreats;
+    }
+
+    public List<String> getTheNotSoGreats() {
+        return theNotSoGreats;
+    }
+    
+    public Optional<String> gimmeAGreat(){
+        return theGreats.stream().collect(toShuffledStream()).findAny();
+    }
+
+    public Optional<String> gimmeANotSoGreat(){
+        return theNotSoGreats.stream().findAny();
+    }
+
+    public static <T> Collector<T, ?, Stream<T>> toShuffledStream() {
+        return Collectors.collectingAndThen(
+                toCollection(ArrayList::new),
+                list -> !list.isEmpty()
+                        ? StreamSupport.stream(new ImprovedRandomSpliterator<>(list, Random::new), false)
+                        : Stream.empty());
+    };
+
+};
+