[add] add example of Stream Operation

brianway · brianway · commit 772c78affcf5 · 2017-03-01T19:49:02.000+08:00
diff --git a/java8/README.md b/java8/README.md
@@ -6,8 +6,11 @@
 
 ## lambda 表达式
 
-- FilteringApples: 传递代码的例子,展示方法引用和Lambda
+- FilteringApples: 传递代码的例子,展示方法引用和 Lambda
 
 
 ## steam API
 
+- Dish: 
+- StreamBasic: 指令式和函数式分别挑选低热量食物名
+- StreamOperation: 流操作:中间操作和终端操作
diff --git a/java8/src/main/java/com/brianway/learning/java8/streamapi/Dish.java b/java8/src/main/java/com/brianway/learning/java8/streamapi/Dish.java
@@ -3,6 +3,9 @@
 import java.util.Arrays;
 import java.util.List;
 
+/**
+ * 菜肴类
+ */
 public class Dish {
 
     private final String name;
@@ -44,6 +47,9 @@ public String toString() {
         return name;
     }
 
+    /**
+     * 菜肴列表
+     */
     public static final List<Dish> menu =
             Arrays.asList(new Dish("pork", false, 800, Dish.Type.MEAT),
                     new Dish("beef", false, 700, Dish.Type.MEAT),
diff --git a/java8/src/main/java/com/brianway/learning/java8/streamapi/StreamOperation.java b/java8/src/main/java/com/brianway/learning/java8/streamapi/StreamOperation.java
@@ -0,0 +1,30 @@
+package com.brianway.learning.java8.streamapi;
+
+import static com.brianway.learning.java8.streamapi.Dish.menu;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Created by brian on 17/2/28.
+ * 流操作:中间操作和终端操作
+ * 流的延迟性质
+ * 1. limit 操作,短路
+ * 2. filter 和 map 操作, 循环合并
+ */
+public class StreamOperation {
+    public static void main(String[] args) {
+        List<String> names = menu.stream()
+                .filter(d -> {
+                    System.out.println("filtering " + d.getName());
+                    return d.getCalories() > 300;
+                })
+                .map(d -> {
+                    System.out.println("mapping " + d.getName());
+                    return d.getName();
+                })
+                .limit(3)
+                .collect(Collectors.toList());
+        System.out.println(names);
+    }
+}
