(yegor256#1349) Add ScalarOfCallable

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

@@ -0,0 +1,44 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2020 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.concurrent.Callable;
+
+/**
+ * ScalarOfCallable.
+ *
+ * @param <T> Element type.
+ * @since 0.47
+ */
+public final class ScalarOfCallable<T> extends ScalarEnvelope<T> {
+
+    /**
+     * Ctor.
+     *
+     * @param callable The callable
+     */
+    public ScalarOfCallable(final Callable<T> callable) {
+        super(callable::call);
+    }
+}

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

@@ -0,0 +1,46 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2020 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 org.cactoos.func.CallableOf;
+import org.junit.jupiter.api.Test;
+import org.llorllale.cactoos.matchers.Assertion;
+import org.llorllale.cactoos.matchers.ScalarHasValue;
+
+/**
+ * Test case for {@link ScalarOfCallable}.
+ *
+ * @since 0.47
+ */
+final class ScalarOfCallableTest {
+    @Test
+    void worksWithCallable() {
+        final Object o = new Object();
+        new Assertion<>(
+            "must hold the same value",
+            new ScalarOfCallable<>(new CallableOf<>(() -> {}, o)),
+            new ScalarHasValue<>(o)
+        ).affirm();
+    }
+}