Add methods $.checkNotNull(), Optional.map(function1) and Optional.orThrow(function).

Author: javadev

src/main/java/com/github/underscore/$.java

@@ -2457,6 +2457,20 @@ public static int lastIndex(final int[] array) {
         return array.length - 1;
     }
 
+    public static <T> T checkNotNull(T reference) {
+        if (reference == null) {
+            throw new NullPointerException();
+        }
+        return reference;
+    }
+
+    public static <T> T checkNotNull(T reference, Object errorMessage) {
+        if (reference == null) {
+            throw new NullPointerException(String.valueOf(errorMessage));
+        }
+        return reference;
+    }
+
     @SuppressWarnings("unchecked")
     protected static <T> List<T> newArrayList() {
         return new ArrayList<T>();

src/main/java/com/github/underscore/Optional.java

@@ -54,6 +54,23 @@ public boolean isPresent() {
         return !absent;
     }
 
+    public <U> Optional<U> map(Function1<? super T, ? extends U> mapper) {
+        $.checkNotNull(mapper);
+        if (!isPresent()) {
+            return absent();
+        } else {
+            return Optional.fromNullable(mapper.apply(arg));
+        }
+    }
+
+    public <X extends Throwable> T orThrow(Function<? extends X> exceptionFunction) throws X {
+        if (absent) {
+            throw exceptionFunction.apply();
+        } else {
+            return arg;
+        }
+    }
+
     @Override
     public boolean equals(final Object o) {
         if (this == o) {

src/test/java/com/github/underscore/UnderscoreTest.java

@@ -263,13 +263,61 @@ public void optional() {
         assertEquals("1", Optional.of(1).or(2).toString());
         assertEquals(null, Optional.absent().orNull());
         assertEquals("1", Optional.of(1).orNull().toString());
+        assertFalse(Optional.<Integer>absent().map(new Function1<Integer, String>() {
+                public String apply(Integer arg) {
+                    return "" + arg;
+                }
+            }).isPresent());
+        assertEquals("1", Optional.of(1).map(new Function1<Integer, String>() {
+                public String apply(Integer arg) {
+                    return "" + arg;
+                }
+            }).get().toString());
         try {
             Optional.absent().get();
             fail("IllegalStateException expected");
         } catch (IllegalStateException ex) {
         }
     }
 
+    @Test(expected = Exception.class)
+    public void optionalOrThrow() throws RuntimeException {
+        Optional.absent().orThrow(new Function<RuntimeException>() {
+            public RuntimeException apply() {
+                return new RuntimeException();
+            }
+        });
+    }
+
+    @Test
+    public void optionalOrThrowWithValue() {
+        assertEquals("1", Optional.of(1).orThrow(new Function<RuntimeException>() {
+            public RuntimeException apply() {
+                return new RuntimeException();
+            }
+        }).toString());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void checkNotNull() {
+        $.checkNotNull(null);
+    }
+
+    @Test
+    public void checkNotNullWithObject() {
+        assertEquals("123", $.checkNotNull("123"));
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void checkNotNullWithMessage() {
+        $.checkNotNull(null, "Error message");
+    }
+
+    @Test
+    public void checkNotNullWithObjectAndMessage() {
+        assertEquals("123", $.checkNotNull("123", "Error message"));
+    }
+
     @Test
     @SuppressWarnings("unchecked")
     public void stackoverflow() {