- add contains #25

Author: brunovinicius

src/main/java/br/com/zbra/androidlinq/AbstractStream.java

@@ -250,6 +250,26 @@ public boolean any(Predicate<T> predicate) {
         return where(predicate).any();
     }
 
+    @Override
+    public boolean contains(final T element) {
+        return contains(element, new EqualityComparator<T>() {
+            @Override
+            public boolean compare(T value1, T value2) {
+                return value1.equals(value2);
+            }
+        });
+    }
+
+    @Override
+    public boolean contains(final T element, final EqualityComparator<T> comparator) {
+        return any(new Predicate<T>() {
+            @Override
+            public boolean apply(T value) {
+                return comparator.compare(value, element);
+            }
+        });
+    }
+
     @Override
     public int count() {
         return aggregate(0, new Aggregator<T, Integer>() {

src/main/java/br/com/zbra/androidlinq/Stream.java

@@ -336,6 +336,23 @@ interface Stream<T> extends Iterable<T> {
      */
     boolean any(Predicate<T> predicate);
 
+    /**
+     * Determines whether a sequence contains a specific element.
+     *
+     * @param element element for checking
+     * @return {@code true} if the source sequence contains the given element; otherwise, {@code false}.
+     */
+    boolean contains(T element);
+
+    /**
+     * Determines whether a sequence contains a specific element.
+     *
+     * @param element element for checking
+     * @param comparator expression defining how to compare elements
+     * @return {@code true} if the source sequence contains the given element; otherwise, {@code false}.
+     */
+    boolean contains(T element, EqualityComparator<T> comparator);
+
     /**
      * Returns the number of elements in a sequence.
      *

src/main/java/br/com/zbra/androidlinq/delegate/EqualityComparator.java

@@ -0,0 +1,5 @@
+package br.com.zbra.androidlinq.delegate;
+
+public interface EqualityComparator<T> {
+    boolean compare(T value1, T value2);
+}

src/test/groovy/br/com/zbra/androidlinq/StreamTest.groovy

@@ -399,6 +399,22 @@ class StreamTest extends GroovyTestCase {
         assert stream(integers).any({ n -> n == 100 } as Predicate) == false
     }
 
+    @SuppressWarnings("GroovyPointlessBoolean")
+    void testContains() {
+        def integers = 0..9
+
+        // contains passing element
+        assert stream(new int[0]).contains(1) == false
+        assert stream(integers).contains(99) == false
+        assert stream(integers).contains(7) == true
+
+        // contains passing element and compare function
+        assert stream([]).contains(9, { n1, n2 -> n1 == n2 }) == false
+        assert stream([1]).contains(1, { n1, n2 -> n1 == n2 }) == true
+        assert stream(integers).contains(9, { n1, n2 -> n1 == n2 }) == true
+        assert stream(integers).contains(100, { n1, n2 -> n1 == n2 }) == false
+    }
+
     void testCount() {
         assert stream([]).count() == 0
         assert stream(0..9).count() == 10