OptionalExample done (Valerii Burmistrov)

src/test/java/option/OptionalExample.java

@@ -4,7 +4,10 @@
 
 import java.util.Optional;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.function.BiFunction;
 import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
 
 import static org.junit.Assert.assertEquals;
 
@@ -52,7 +55,124 @@ public void map() {
 
     private Optional<String> getOptional() {
         return ThreadLocalRandom.current().nextBoolean()
-            ? Optional.empty()
-            : Optional.of("abc");
+                ? Optional.empty()
+                : Optional.of("abc");
     }
-}
+
+    public static <T1, T2, R> Optional<R> zipMap(Option<T1> o1, Option<T2> o2, BiFunction<T1, T2, R> function) {
+        //dont use isPresent, get, mutable variables// nonstatic - use static
+        //use map, flatMap
+        throw new UnsupportedOperationException();
+    }
+
+    @Test
+    public void orElse() {
+        final Optional<String> optional = getOptional();
+
+        final String string = "someString";
+
+        final String expected = optional.orElse(string);
+
+        final String actual;
+
+        if (optional.isPresent()) {
+            actual = optional.get();
+        } else {
+            actual = string;
+        }
+
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void orElseGet() {
+        final Optional<String> optional = getOptional();
+
+        final Supplier<String> supplier = () -> "someString";
+
+        final String expected = optional.orElseGet(supplier);
+
+        final String actual;
+
+        if (optional.isPresent()) {
+            actual = optional.get();
+        } else {
+            actual = supplier.get();
+        }
+
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void orElseThrow() {
+        final Optional<String> optional = getOptional();
+
+        final Supplier<NullPointerException> supplier = NullPointerException::new;
+
+        String expected = null;
+
+        Throwable exception = new Throwable();
+
+        try {
+            expected = optional.orElseThrow(supplier);
+        } catch (NullPointerException e) {
+            exception = e;
+        }
+
+        String actual = null;
+
+        try {
+            if (optional.isPresent()) {
+                actual = optional.get();
+            } else {
+                supplier.get();
+            }
+        } catch (NullPointerException e) {
+            assertEquals(exception.getClass(), e.getClass());
+        }
+
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void filter() {
+        final Optional<String> optional = getOptional();
+
+        final Predicate<String> predicate = s -> s.equals("someString");
+
+        Optional<String> expected = optional.filter(predicate);
+
+        Optional<String> actual;
+
+        if (optional.isPresent()) {
+            if (predicate.test(optional.get())) {
+                actual = optional;
+            } else {
+                actual = Optional.empty();
+            }
+        } else {
+            actual = Optional.empty();
+        }
+
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void flatMap() {
+        final Optional<String> optional = getOptional();
+
+        final Function<String, Optional<String>> function = s -> Optional.of("someString");
+
+        Optional<String> expected = optional.flatMap(function);
+
+        Optional<String> actual;
+
+        if (optional.isPresent()) {
+            actual = function.apply(optional.get());
+        } else {
+            actual = Optional.empty();
+        }
+
+        assertEquals(expected, expected);
+    }
+}