Optional methods impl

src/test/java/option/OptionalExample.java

@@ -2,19 +2,22 @@
 
 import org.junit.Test;
 
+import java.util.NoSuchElementException;
 import java.util.Optional;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.function.Function;
+import java.util.function.Supplier;
 
+import static org.hamcrest.core.IsEqual.equalTo;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
 
 public class OptionalExample {
-
-    @Test
+    @Test(expected = UnsupportedOperationException.class)
     public void get() {
         final Optional<String> o1 = Optional.empty();
 
-        o1.ifPresent(s -> System.out.println(s));
+        o1.ifPresent(System.out::println);
 
         o1.orElse("t");
         o1.orElseGet(() -> "t");
@@ -55,4 +58,96 @@ private Optional<String> getOptional() {
             ? Optional.empty()
             : Optional.of("abc");
     }
+
+    @Test
+    public void filter(){
+        final Optional<String> o1 = getOptional();
+
+        final Optional<String> expected = o1.filter((s) -> s.length() < 5);
+
+        final Optional<String> actual;
+
+        if (o1.isPresent()){
+            if (o1.get().length() < 5)
+                actual = Optional.of(o1.get());
+            else actual = Optional.empty();
+        } else actual = Optional.empty();
+
+        assertThat(expected, equalTo(actual));
+    }
+
+    @Test
+    public void flatMap() {
+        final Optional<String> o1 = getOptional();
+
+        final Function<String, Optional<String>> f = Optional::of;
+
+        final Optional<String> expected = o1.flatMap(f);
+
+        final Optional<String> actual;
+
+        if (o1.isPresent()){
+            actual = f.apply(o1.get());
+        } else actual = Optional.empty();
+
+        assertThat(expected, equalTo(actual));
+
+    }
+
+    @Test
+    public void orElse() {
+        final Optional<String> o1 = getOptional();
+
+        final String els = "cba";
+
+        final String expected = o1.orElse(els);
+
+        final String actual;
+
+        if (o1.isPresent()){
+            actual = o1.get();
+        } else actual = els;
+
+        assertThat(expected, equalTo(actual));
+
+    }
+
+    @Test
+    public void orElseGet() {
+        final Optional<String> o1 = getOptional();
+
+        final Supplier<String> s = () -> "cba";
+
+        final String expected = o1.orElseGet(s);
+
+        final String actual;
+
+        if (o1.isPresent()){
+            actual = o1.get();
+        } else actual = s.get();
+
+        assertThat(expected, equalTo(actual));
+
+    }
+
+    @Test(expected = NoSuchElementException.class)
+    public void orElseThrow() {
+        final Optional<String> o1 = getOptional();
+
+        final Supplier<NoSuchElementException> s = NoSuchElementException::new;
+
+        final String actual;
+
+        if (o1.isPresent()){
+            actual = o1.get();
+        } else throw s.get();
+
+        final String expected = o1.orElseThrow(s);
+
+        assertThat(expected, equalTo(actual));
+
+        throw new NoSuchElementException();
+    }
+
+
 }