Using Collection as an internal storage for Stream wrappers

Author: Damtev

utbot-framework/src/main/java/org/utbot/engine/overrides/collections/Collection.java

@@ -7,21 +7,13 @@
 
 @UtClassMock(target = java.util.Collection.class, internalUsage = true)
 public interface Collection<E> extends java.util.Collection<E> {
-    @SuppressWarnings("unchecked")
     @Override
-    default Stream<E> parallelStream() {
-        Object[] data = toArray();
-        int size = data.length;
-
-        return new UtStream<>((E[]) data, size);
+    default Stream<E> stream() {
+        return new UtStream<>(this);
     }
 
-    @SuppressWarnings("unchecked")
     @Override
-    default Stream<E> stream() {
-        Object[] data = toArray();
-        int size = data.length;
-
-        return new UtStream<>((E[]) data, size);
+    default Stream<E> parallelStream() {
+        return stream();
     }
 }

utbot-framework/src/main/java/org/utbot/engine/overrides/collections/UtArrayList.java

@@ -64,10 +64,16 @@ public UtArrayList(Collection<? extends E> c) {
     }
 
     public UtArrayList(E[] data) {
+        this(data, 0, data.length);
+    }
+
+    public UtArrayList(E[] data, int startInclusive, int endExclusive) {
         visit(this);
-        int length = data.length;
+
+        int length = endExclusive - startInclusive;
+
         elementData = new RangeModifiableUnlimitedArray<>();
-        elementData.setRange(0, data, 0, length);
+        elementData.setRange(0, data, startInclusive, length);
         elementData.end = length;
     }
 
@@ -372,21 +378,6 @@ public void replaceAll(UnaryOperator<E> operator) {
         }
     }
 
-    @Override
-    public Stream<E> stream() {
-        preconditionCheck();
-
-        int size = elementData.end;
-        E[] data = elementData.toCastedArray(0, size);
-
-        return new UtStream<>(data, size);
-    }
-
-    @Override
-    public Stream<E> parallelStream() {
-        return stream();
-    }
-
     /**
      * Auxiliary method, that should be only executed concretely
      * @return new ArrayList with all the elements from this.

utbot-framework/src/main/java/org/utbot/engine/overrides/collections/UtHashSet.java

@@ -266,21 +266,6 @@ public Iterator<E> iterator() {
         return new UtHashSetIterator();
     }
 
-    @Override
-    public Stream<E> stream() {
-        preconditionCheck();
-
-        int size = elementData.end;
-        E[] data = elementData.toCastedArray(0, size);
-
-        return new UtStream<>(data, size);
-    }
-
-    @Override
-    public Stream<E> parallelStream() {
-        return stream();
-    }
-
     public class UtHashSetIterator implements Iterator<E> {
         int index = 0;
 

utbot-framework/src/main/java/org/utbot/engine/overrides/collections/UtLinkedList.java

@@ -451,22 +451,6 @@ public Iterator<E> descendingIterator() {
         preconditionCheck();
         return new ReverseIteratorWrapper(elementData.end);
     }
-
-    @Override
-    public Stream<E> stream() {
-        preconditionCheck();
-
-        int size = elementData.end;
-        E[] data = elementData.toCastedArray(0, size);
-
-        return new UtStream<>(data, size);
-    }
-
-    @Override
-    public Stream<E> parallelStream() {
-        return stream();
-    }
-
     public class ReverseIteratorWrapper implements ListIterator<E> {
 
         int index;

utbot-framework/src/main/java/org/utbot/engine/overrides/stream/Stream.java

@@ -8,27 +8,24 @@
 
 import static org.utbot.engine.overrides.UtOverrideMock.executeConcretely;
 
-@SuppressWarnings("unused")
 @UtClassMock(target = java.util.stream.Stream.class, internalUsage = true)
 public interface Stream<E> extends BaseStream<E, Stream<E>> {
     @SuppressWarnings("unchecked")
     static <E> java.util.stream.Stream<E> of(E element) {
-        Object[] data = new Object[1];
+        E[] data = (E[]) new Object[1];
         data[0] = element;
 
-        return new UtStream<>((E[]) data, 1);
+        return new UtStream<>(data);
     }
 
     @SuppressWarnings("unchecked")
     static <E> java.util.stream.Stream<E> of(E... elements) {
-        int size = elements.length;
-
-        return new UtStream<>(elements, size);
+        return new UtStream<>(elements);
     }
 
     @SuppressWarnings("unchecked")
     static <E> java.util.stream.Stream<E> empty() {
-        return new UtStream<>((E[]) new Object[]{}, 0);
+        return new UtStream<>((E[]) new Object[]{});
     }
 
     static <E> java.util.stream.Stream<E> generate(Supplier<E> s) {

utbot-framework/src/main/java/org/utbot/engine/overrides/stream/SubCollectionView.java

@@ -0,0 +1,59 @@
+package org.utbot.engine.overrides.stream;
+
+import java.util.AbstractCollection;
+import java.util.Collection;
+import java.util.Iterator;
+
+public class SubCollectionView<E> extends AbstractCollection<E> {
+    private final Collection<E> innerCollection;
+
+    private final int fromInclusive;
+    private final int endExclusive;
+
+    public SubCollectionView(Collection<E> innerCollection, int fromInclusive, int endExclusive) {
+        this.innerCollection = innerCollection;
+        this.fromInclusive = fromInclusive;
+        this.endExclusive = endExclusive;
+    }
+
+    public SubCollectionView(Collection<E> innerCollection, int fromInclusive) {
+        this(innerCollection, fromInclusive, innerCollection.size());
+    }
+
+    @Override
+    public Iterator<E> iterator() {
+        final Iterator<E> iterator = innerCollection.iterator();
+
+        // skip first elements
+        for (int i = 0; i < fromInclusive; i++) {
+            iterator.next();
+        }
+
+        return new SubCollectionViewIterator(iterator);
+    }
+
+    @Override
+    public int size() {
+        return endExclusive - fromInclusive;
+    }
+
+    private class SubCollectionViewIterator implements Iterator<E> {
+        private final Iterator<E> innerIterator;
+
+        private final int index = fromInclusive;
+
+        public SubCollectionViewIterator(Iterator<E> innerIterator) {
+            this.innerIterator = innerIterator;
+        }
+
+        @Override
+        public boolean hasNext() {
+            return index < endExclusive && innerIterator.hasNext();
+        }
+
+        @Override
+        public E next() {
+            return innerIterator.next();
+        }
+    }
+}

utbot-framework/src/main/java/org/utbot/engine/overrides/stream/UtDoubleStream.java

@@ -139,7 +139,7 @@ public <U> Stream<U> mapToObj(DoubleFunction<? extends U> mapper) {
             mapped[i] = mapper.apply(elementData.get(i));
         }
 
-        return new UtStream<>((U[]) mapped, size);
+        return new UtStream<>((U[]) mapped);
     }
 
     @Override
@@ -544,7 +544,7 @@ public Stream<Double> boxed() {
             elements[i] = elementData.get(i);
         }
 
-        return new UtStream<>(elements, size);
+        return new UtStream<>(elements);
     }
 
     @Override

utbot-framework/src/main/java/org/utbot/engine/overrides/stream/UtIntStream.java

@@ -140,7 +140,7 @@ public <U> Stream<U> mapToObj(IntFunction<? extends U> mapper) {
             mapped[i] = mapper.apply(elementData.get(i));
         }
 
-        return new UtStream<>(mapped, size);
+        return new UtStream<>(mapped);
     }
 
     @Override
@@ -586,7 +586,7 @@ public Stream<Integer> boxed() {
             elements[i] = elementData.get(i);
         }
 
-        return new UtStream<>(elements, size);
+        return new UtStream<>(elements);
     }
 
     @Override

utbot-framework/src/main/java/org/utbot/engine/overrides/stream/UtLongStream.java

@@ -140,7 +140,7 @@ public <U> Stream<U> mapToObj(LongFunction<? extends U> mapper) {
             mapped[i] = mapper.apply(elementData.get(i));
         }
 
-        return new UtStream<>((U[]) mapped, size);
+        return new UtStream<>((U[]) mapped);
     }
 
     @Override
@@ -562,7 +562,7 @@ public Stream<Long> boxed() {
             elements[i] = elementData.get(i);
         }
 
-        return new UtStream<>(elements, size);
+        return new UtStream<>(elements);
     }
 
     @Override