Homework option

src/test/java/option/OptionalExample.java

@@ -1,10 +1,18 @@
 package option;
 
+import org.apache.commons.lang3.ObjectUtils;
+import org.junit.Assert;
 import org.junit.Test;
 
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
 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 +60,117 @@ public void map() {
 
     private Optional<String> getOptional() {
         return ThreadLocalRandom.current().nextBoolean()
-            ? Optional.empty()
-            : Optional.of("abc");
+                ? Optional.empty()
+                : Optional.of("abc");
+    }
+
+    @Test
+    public void filter() {
+        final Optional<String> o1 = getOptional();
+        final Predicate<String> predicate = s -> s.equals("test");
+        Optional<String> expected = o1.filter(predicate);
+        Optional<String> actual;
+        if (o1.isPresent()) {
+            if (predicate.test(o1.get())) {
+                actual = o1;
+            } else {
+                actual = o1.empty();
+            }
+        } else {
+            actual = o1.empty();
+        }
+
+        assertEquals(expected, actual);
+
+    }
+
+    @Test
+    public void flatMap() {
+        final Optional<String> o1 = getOptional();
+
+        final Function<String, Optional<String>> function = s -> Optional.of("test");
+        Optional<String> expected = o1.flatMap(function);
+        Optional<String> actual;
+        if (o1.isPresent()) {
+            actual = function.apply(o1.get());
+        } else {
+            actual = Optional.empty();
+        }
+
+        assertEquals(expected, actual);
+
+    }
+
+    @Test
+    public void orElse() {
+        final Optional<String> o1 = getOptional();
+        String expected = o1.orElse("other");
+        String actual;
+        if (o1.isPresent()) {
+            actual = o1.get();
+        } else {
+            actual = "other";
+        }
+
+        assertEquals(expected, actual);
+
+    }
+
+    @Test
+    public void orElseThrow() {
+        final Optional<String> o1 = getOptional();
+        final Supplier<NullPointerException> supplier = NullPointerException::new;
+        String expected = null;
+        String actual = null;
+        Throwable exception = new Throwable();
+
+        try {
+            expected = o1.orElseThrow(supplier);
+        } catch (NullPointerException e) {
+            exception = e;
+        }
+
+        try {
+            if (o1.isPresent()) {
+                actual = o1.get();
+            } else {
+                supplier.get();
+            }
+        } catch (NullPointerException e) {
+            assertEquals(exception.getClass(), e.getClass());
+        }
+
+        assertEquals(expected, actual);
+
+    }
+
+    @Test
+    public void orElseGet() {
+        final Optional<String> o1 = getOptional();
+        final Supplier<String> supplier = () -> "test";
+        final String expected = o1.orElseGet(supplier);
+        String actual;
+
+        if(o1.isPresent()){
+            actual = o1.get();
+        }else{
+            actual = supplier.get();
+        }
+
+        assertEquals(expected,actual);
+
+    }
+
+
+    //TODO method zip
+    public static <T1, T2, R> Optional<R> zipMap(Optional<T1> o1, Optional<T2> o2, BiFunction<T1, T2, R> f) {
+        return o1.flatMap(x -> o2.map(y -> f.apply(x,y)));
+    }
+
+    @Test
+    public void testZipMap(){
+        final BiFunction<Integer,Integer,Integer> f = Integer::max;
+        assertEquals(zipMap(Optional.of(0), Optional.of(1), f),  Optional.of(1));
+        assertEquals(zipMap(Optional.empty(), Optional.of(1), f), Optional.empty());
     }
 }