Changming Li

src/main/java/cn/nextop/rxjava/share/practices/Practice1.java

@@ -1,35 +1,36 @@
-/*
- * Copyright 2016-2017 Leon Chen
- *
- * 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 cn.nextop.rxjava.share.practices;
-
-import cn.nextop.rxjava.share.util.type.Tuple2;
-import io.reactivex.Observable;
-
-/**
- * @author Baoyi Chen
- */
-public class Practice1 {
-
-    /*
-     * 举例如下:
-     * 参数 Observable["a","b","c"]
-     * 返回值 Observable[(1, "a"), (2, "b"), (3, "c")] 注意index从1开始
-     */
-    public Observable<Tuple2<Integer, String>> indexable(Observable<String> observable) {
-        throw new UnsupportedOperationException("implementation");
-    }
-}
+/*
+ * Copyright 2016-2017 Leon Chen
+ *
+ * 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 cn.nextop.rxjava.share.practices;
+
+import cn.nextop.rxjava.share.util.Tuples;
+import cn.nextop.rxjava.share.util.type.Tuple2;
+import io.reactivex.Observable;
+
+/**
+ * @author Baoyi Chen
+ */
+public class Practice1 {
+
+    /*
+     * 举例如下:
+     * 参数 Observable["a","b","c"]
+     * 返回值 Observable[(1, "a"), (2, "b"), (3, "c")] 注意index从1开始
+     */
+    public Observable<Tuple2<Integer, String>> indexable(Observable<String> observable) {
+        return Observable.zip(observable, Observable.range(1, Integer.MAX_VALUE), (a, b) -> Tuples.of(b, a));
+    }
+}

src/main/java/cn/nextop/rxjava/share/practices/Practice2.java

@@ -1,49 +1,53 @@
-/*
- * Copyright 2016-2017 Leon Chen
- *
- * 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 cn.nextop.rxjava.share.practices;
-
-
-import cn.nextop.rxjava.share.util.type.Tuple2;
-import io.reactivex.Observable;
-import io.reactivex.Single;
-
-import java.util.Map;
-
-/**
- * @author Baoyi Chen
- */
-public class Practice2 {
-
-    /*
-     * 举例:
-     * words = Observable["a", "a", "b", "c", "c"]
-     * 返回: Observable[("a", 2), ("b", 1), ("c", 2)]
-     */
-    public Observable<Tuple2<String, Integer>> wordCount1(Observable<String> words) {
-        throw new UnsupportedOperationException("implementation");
-    }
-
-    /*
-     * 举例:
-     * words = Observable["a", "a", "b", "c", "c"]
-     * 返回: Single[Map{a=2, b=1, c=2}]
-     */
-    public Single<Map<String, Integer>> wordCount2(Observable<String> words) {
-        throw new UnsupportedOperationException("implementation");
-    }
-
-}
+/*
+ * Copyright 2016-2017 Leon Chen
+ *
+ * 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 cn.nextop.rxjava.share.practices;
+
+
+import cn.nextop.rxjava.share.util.Tuples;
+import cn.nextop.rxjava.share.util.type.Tuple2;
+import io.reactivex.*;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author Baoyi Chen
+ */
+public class Practice2 {
+
+    /*
+     * 举例:
+     * words = Observable["a", "a", "b", "c", "c"]
+     * 返回: Observable[("a", 2), ("b", 1), ("c", 2)]
+     */
+    public Observable<Tuple2<String, Integer>> wordCount1(Observable<String> words) {
+        return words.groupBy(string -> string).flatMap(observable-> observable.count().toObservable().map(count-> Tuples.of(observable.getKey(),count.intValue())));
+    }
+
+    /*
+     * 举例:
+     * words = Observable["a", "a", "b", "c", "c"]
+     * 返回: Single[Map{a=2, b=1, c=2}]
+     */
+    public Single<Map<String, Integer>> wordCount2(Observable<String> words) {
+        return words.reduce(new HashMap<>(), (map, s) -> {
+            map.put(s, map.get(s) == null ? 1 : map.get(s) +1);
+            return map;
+        });
+    }
+
+}

src/main/java/cn/nextop/rxjava/share/practices/Practice3.java

@@ -1,60 +1,64 @@
-/*
- * Copyright 2016-2017 Leon Chen
- *
- * 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 cn.nextop.rxjava.share.practices;
-
-import io.reactivex.Maybe;
-import io.reactivex.Observable;
-
-/**
- * @author Baoyi Chen
- */
-public class Practice3 {
-
-    /*
-     * 根据iterate的结果求和
-     */
-    public Maybe<Integer> sum(Observable<Node> observable) {
-        throw new UnsupportedOperationException("implementation");
-    }
-
-    /*
-     * 举例:
-     *                 5
-     *                / \
-     *               6   7
-     *              / \   \
-     *             4   3  nil
-     *
-     * return Observable[4, 3, 6, 7, 5] 顺序无关
-     */
-    public Observable<Integer> iterate(Observable<Node> observable) {
-        throw new UnsupportedOperationException("implementation");
-    }
-
-    public static class Node {
-        public Node left;
-        public Node right;
-        public int value;
-
-        public Node(Node left, Node right, int value) {
-            this.left = left;
-            this.right = right;
-            this.value = value;
-        }
-    }
-
-}
+/*
+ * Copyright 2016-2017 Leon Chen
+ *
+ * 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 cn.nextop.rxjava.share.practices;
+
+import io.reactivex.*;
+
+/**
+ * @author Baoyi Chen
+ */
+public class Practice3 {
+
+    /*
+     * 根据iterate的结果求和
+     */
+    public Maybe<Integer> sum(Observable<Node> observable) {
+        return iterate(observable).reduce((x, y) -> x + y);
+    }
+
+    /*
+     * 举例:
+     *                 5
+     *                / \
+     *               6   7
+     *              / \   \
+     *             4   3  nil
+     *
+     * return Observable[4, 3, 6, 7, 5] 顺序无关
+     */
+    public Observable<Integer> iterate(Observable<Node> observable) {
+        return observable.flatMap(e -> {
+            Observable<Integer> left = e.left == null ? Observable.empty() : iterate(Observable.just(e.left));
+            Observable<Integer> right = e.right == null ? Observable.empty() : iterate(Observable.just(e.right));
+            Observable<Integer> value = Observable.just(e.value);
+            return Observable.merge(left, right, value);
+        });
+    }
+
+    public static class Node {
+        public Node left;
+        public Node right;
+        public int value;
+
+        public Node(Node left, Node right, int value) {
+            this.left = left;
+            this.right = right;
+            this.value = value;
+        }
+    }
+
+}