Merge pull request #47 from alexengrig/fix/36

Fixes #36

Author: alexengrig

README.md

@@ -28,6 +28,53 @@ This library contains utility classes with useful lambdas.
 *   Writing code in [declarative](https://en.wikipedia.org/wiki/Declarative_programming) style.
 *   Writing code in chaining style.
 
+## Examples
+
+Get the value from `Map` and print it on the console:
+
+```java
+    Map<Integer, String> map = new HashMap<>();
+    map.put(1, "one");
+    Holder<Map<Integer, String>> holder = new Holder<>(map);
+// Plain Java
+    Map<Integer, String> map = holder.get();
+    String actual = map.get(key);
+    System.out.println(actual);
+// Chaining Style
+    Optional.of(holder)
+            .map(Holder::get)
+            .map(m -> m.get(key))
+            .ifPresent(System.out::println);
+// LambdaX
+    String actual = Optional.of(holder)
+             .map(Holder::get)
+             .map(MapX.get(key))
+             .ifPresent(System.out::println);
+```
+
+Insert the value into `Collection` if it does not contain it:
+
+```java
+    Collection<Integer> numbers = new ArrayList<>();
+    Holder<Collection<Integer>> holder = new Holder<>(numbers);
+    int value = 1;
+// Plain Java
+    Collection<Integer> target = holder.get();
+    if (!target.contains(value)) {
+        target.add(value);
+    }
+// Chaining Style  
+    Optional.of(holder)
+            .map(Holder::get)
+            .filter(collection -> !collection.contains(value))
+            .ifPresent(collection -> collection.add(value));
+// LambdaX
+    Optional.of(holder)
+            .map(Holder::get)
+            .filter(CollectionX.contains(value).negate())
+            .ifPresent(CollectionX.onlyAdd(value));
+```
+
 ## Installation
 
 Releases are available in [Maven Central](https://repo1.maven.org/maven2/io/github/alexengrig/lambdax/).

src/test/java/io/github/alexengrig/lambdax/example/CollectionExampleTest.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2019 LambdaX contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.alexengrig.lambdax.example;
+
+import io.github.alexengrig.lambdax.collection.CollectionX;
+import io.github.alexengrig.lambdax.collection.MapX;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Abbreviations:
+ * <pre>
+ *     PS - Plain Style
+ *     CS - Chaining Style
+ *     LX - LambdaX
+ * </pre>
+ */
+public class CollectionExampleTest {
+    private Holder<Map<Integer, String>> mapHolder;
+    private Holder<Collection<Integer>> collectionHolder;
+
+    @Before
+    public void before() {
+        HashMap<Integer, String> numbers = new HashMap<>();
+        numbers.put(1, "one");
+        numbers.put(2, "two");
+        numbers.put(3, "three");
+        mapHolder = new Holder<>(numbers);
+        collectionHolder = new Holder<>(new ArrayList<>());
+    }
+
+    @Test
+    public void checkMapGettingInPS() {
+        int value = 1;
+        Map<Integer, String> map = mapHolder.get();
+        String actual = map.get(value);
+        assertEquals("one", actual);
+    }
+
+    @Test
+    public void checkMapGettingInCS() {
+        int value = 1;
+        String actual = Optional.of(mapHolder)
+                .map(Holder::get)
+                .map(m -> m.get(value))
+                .orElseThrow(IllegalStateException::new);
+        assertEquals("one", actual);
+    }
+
+    @Test
+    public void checkMapGettingInLX() {
+        int value = 1;
+        String actual = Optional.of(mapHolder)
+                .map(Holder::get)
+                .map(MapX.get(value))
+                .orElseThrow(IllegalStateException::new);
+        assertEquals("one", actual);
+    }
+
+    @Test
+    public void checkInsertItemInPS() {
+        int value = 2;
+        Collection<Integer> collection = collectionHolder.get();
+        if (!collection.contains(value)) {
+            collection.add(value);
+        }
+        assertTrue(collectionHolder.get().contains(value));
+    }
+
+    @Test
+    public void checkInsertItemInCS() {
+        int value = 2;
+        Optional.of(collectionHolder)
+                .map(Holder::get)
+                .filter(collection -> !collection.contains(value))
+                .ifPresent(collection -> collection.add(value));
+        assertTrue(collectionHolder.get().contains(value));
+    }
+
+    @Test
+    public void checkInsertItemInLX() {
+        int value = 2;
+        Optional.of(collectionHolder)
+                .map(Holder::get)
+                .filter(CollectionX.contains(value).negate())
+                .ifPresent(CollectionX.onlyAdd(value));
+        assertTrue(collectionHolder.get().contains(value));
+    }
+}

src/test/java/io/github/alexengrig/lambdax/example/Holder.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2019 LambdaX contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.alexengrig.lambdax.example;
+
+final class Holder<T> {
+    private T t;
+
+    Holder(T t) {
+        this.t = t;
+    }
+
+    T get() {
+        return t;
+    }
+
+    void set(T t) {
+        this.t = t;
+    }
+}