Chuvakhin Ivan, Optional

src/test/java/option/OptionalExample.java

@@ -5,6 +5,8 @@
 import java.util.Optional;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
 
 import static org.junit.Assert.assertEquals;
 
@@ -32,6 +34,101 @@ public void ifPresent() {
         }
     }
 
+    @Test
+    public void filter() {
+        final Optional<String> o1 = getOptional();
+
+        final Predicate<String> isEmpty = String::isEmpty;
+
+        final Optional<String> expected = o1.filter(isEmpty);
+
+        final Optional<String> actual;
+        if (o1.isPresent()) {
+            if (isEmpty.test(o1.get())) {
+                actual = Optional.of(o1.get());
+            } else {
+                actual = Optional.empty();
+            }
+        } else {
+            actual = Optional.empty();
+        }
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void flatMap() {
+        final Optional<String> o1 = getOptional();
+
+        final Function<String, Optional<String>> optionalFunction = (g) -> Optional.of(g + "abc");
+
+        final Optional<String> expected = o1.flatMap(optionalFunction);
+
+        final Optional<String> actual;
+        if (o1.isPresent()) {
+            actual = optionalFunction.apply(o1.get());
+        } else {
+            actual = Optional.empty();
+        }
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void orElse() {
+        final Optional<String> o1 = getOptional();
+
+        final String abc = "abc";
+
+        final Optional<String> expected = Optional.of(o1.orElse(abc));
+
+        final Optional<String> actual;
+
+        if (o1.isPresent()) {
+            actual = Optional.of(o1.get());
+        } else {
+            actual = Optional.of(abc);
+        }
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void orElseGet() {
+        final Optional<String> o1 = getOptional();
+
+        final Supplier<String> supplier = () -> "abc";
+
+        final Optional<String> expected = Optional.of(o1.orElseGet(supplier));
+
+        final Optional<String> actual;
+
+        if (o1.isPresent()) {
+            actual = Optional.of(o1.get());
+        } else {
+            actual = Optional.of(supplier.get());
+        }
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void orElseThrow() {
+        final Optional<String> o1 = getOptional();
+
+        final Supplier<RuntimeException> supplier = () -> new NullPointerException("Another NPE");
+        try {
+            final Optional<String> expected = Optional.of(o1.orElseThrow(supplier));
+
+            final Optional<String> actual;
+
+            if (o1.isPresent()) {
+                actual = Optional.of(o1.get());
+            } else {
+                throw supplier.get();
+            }
+            assertEquals(expected, actual);
+        } catch (NullPointerException e) {
+            assertEquals(e.getClass(), NullPointerException.class);
+        }
+    }
+
     @Test
     public void map() {
         final Optional<String> o1 = getOptional();
@@ -52,7 +149,7 @@ public void map() {
 
     private Optional<String> getOptional() {
         return ThreadLocalRandom.current().nextBoolean()
-            ? Optional.empty()
-            : Optional.of("abc");
+                ? Optional.empty()
+                : Optional.of("abc");
     }
 }