Merge branch '__rultor'

src/main/java/org/cactoos/scalar/Folded.java

@@ -0,0 +1,87 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.scalar;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import org.cactoos.BiFunc;
+import org.cactoos.Scalar;
+
+/**
+ * Folds iterable via BiFunc
+ *
+ * <p>There is no thread-safety guarantee.
+ *
+ * <p>This class implements {@link Scalar}, which throws a checked
+ * {@link Exception}. This may not be convenient in many cases. To make
+ * it more convenient and get rid of the checked exception you can
+ * use {@link UncheckedScalar} or {@link IoCheckedScalar} decorators.</p>
+ *
+ * @author Alexander Dyadyushenko (gookven@gmail.com)
+ * @author Eduard Balovnev (bedward70@mail.ru)
+ * @version $Id$
+ * @param <T> Scalar type
+ * @since 0.9
+ */
+public final class Folded<T> implements Scalar<T> {
+
+    /**
+     * Items.
+     */
+    private final Iterable<Scalar<T>> items;
+
+    /**
+     * Folding function.
+     */
+    private final BiFunc<T, T, T> function;
+
+    /**
+     * Ctor.
+     * @param fold Folding function
+     * @param scalars The scalars
+     */
+    public Folded(
+        final BiFunc<T, T, T> fold,
+        final Iterable<Scalar<T>> scalars
+    ) {
+        this.items = scalars;
+        this.function = fold;
+    }
+
+    @Override
+    public T value() throws Exception {
+        final Iterator<Scalar<T>> iter = this.items.iterator();
+        if (!iter.hasNext()) {
+            throw new NoSuchElementException(
+                "Can't find first element in an empty iterable"
+            );
+        }
+        T acc = iter.next().value();
+        while (iter.hasNext()) {
+            final T next = iter.next().value();
+            acc = this.function.apply(acc, next);
+        }
+        return acc;
+    }
+}

src/test/java/org/cactoos/scalar/FoldedTest.java

@@ -0,0 +1,103 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.scalar;
+
+import java.util.Collections;
+import java.util.NoSuchElementException;
+import org.cactoos.Scalar;
+import org.cactoos.iterable.IterableOf;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+/**
+ * Test case for {@link Folded}.
+ *
+ * @author Eduard Balovnev (bedward70@mail.ru)
+ * @version $Id$
+ * @since 1.0
+ * @checkstyle JavadocMethodCheck (500 lines)
+ */
+public final class FoldedTest {
+
+    @Test(expected = NoSuchElementException.class)
+    public void failsForEmptyIterable() throws Exception {
+        new Folded<>(
+            (first, last) -> first,
+            Collections.emptyList()
+        )
+            .value();
+    }
+
+    @Test
+    public void singleAtSingleIterable() throws Exception {
+        final Integer single = 10;
+        MatcherAssert.assertThat(
+            "Can't find the single",
+            new Folded<>(
+                (first, last) -> first,
+                new IterableOf<Scalar<Integer>>(() -> single)
+            ).value(),
+            Matchers.equalTo(single)
+        );
+    }
+
+    @Test
+    public void firstAtIterable() throws Exception {
+        final String one = "Apple";
+        final String two = "Banana";
+        final String three = "Orange";
+        MatcherAssert.assertThat(
+            "Can't find the first",
+            new Folded<>(
+                (first, last) -> first,
+                new IterableOf<Scalar<String>>(
+                    () -> one,
+                    () -> two,
+                    () -> three
+                )
+            ).value(),
+            Matchers.equalTo(one)
+        );
+    }
+
+    @Test
+    public void lastAtIterable() throws Exception {
+        final Character one = 'A';
+        final Character two = 'B';
+        final Character three = 'O';
+        MatcherAssert.assertThat(
+            "Can't find the last",
+            new Folded<>(
+                (first, last) -> last,
+                new IterableOf<Scalar<Character>>(
+                    () -> one,
+                    () -> two,
+                    () -> three
+                )
+            ).value(),
+            Matchers.equalTo(three)
+        );
+    }
+}