lambda and high order

data/3.Java高阶/1.通过行为参数化传递代码/1.行为参数化/config.json

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data/3.Java高阶/1.通过行为参数化传递代码/2.简写/config.json

-{
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-  ],
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data/3.Java高阶/1.通过行为参数化传递代码/3.高序函数/config.json

-{
-  "node_id": "java-db33d9c7f2004cdbbc058254fe536ace",
-  "keywords": [],
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-  "title": "真实的例子"
-}
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data/3.Java高阶/1.通过行为参数化传递代码/config.json

@@ -2,6 +2,9 @@
   "node_id": "java-fb711fb0dfbb40db974476ea2d9faf9d",
   "keywords": [],
   "children": [],
-  "export": [],
+  "export": [
+    "map.json",
+    "sum.json"
+  ],
   "title": "通过行为参数化传递代码"
 }
\ No newline at end of file

data/3.Java高阶/1.通过行为参数化传递代码/filter.json

+{
+  "type": "code_options",
+  "author": "刘鑫",
+  "source": "double.md",
+  "notebook_enable": false
+}
\ No newline at end of file

data/3.Java高阶/1.通过行为参数化传递代码/filter.md

+# 过滤
+
+Stream API支持 filter 方法，接受一段过滤代码，使得调用者可以传入过滤规则，返回过滤后的新的 Stream，那么下列调用代码不正确的是：
+
+## 答案
+
+```java
+    IntStream stream=IntStream.range(0,100);
+        return stream.filter(x%2==0);
+```
+
+## 选项
+
+### 标准的 lambda 调用
+
+```java
+    IntStream stream=IntStream.range(0,100);
+    return stream.filter(x->x%2==0);
+```
+
+### lambda 的完整形式
+
+```java
+    IntStream stream=IntStream.range(0,100);
+        return stream.filter(x->{
+        return x%2==0;
+    });
+```
+
+### 对象方法引用
+
+```java
+    IntStream stream=IntStream.range(0,100);
+    return stream.filter(this::isEven);
+```
+
+### 类型方法引用
+
+```java
+    IntStream stream=IntStream.range(0,100);
+    return stream.filter(App::isEven);
+```
+
+### 可以显式使用完整的函数对象定义
+
+```java
+    IntStream stream=IntStream.range(0,100);
+    IntPredicate filter = new IntPredicate() {
+            @Override
+            public boolean test(int value) {
+                    return value % 2 == 0;
+            }
+        };
+    return stream.filter(filter);
+```
\ No newline at end of file

data/3.Java高阶/1.通过行为参数化传递代码/map.md

+# 翻倍操作
+
+下面哪个选项可以从 `Stream<Integer> stream` 构造一个新的 List<Ineger> 对象，使其包含stream中每个元素翻倍后的结果：
+
+## template
+
+```java
+import java.util.stream.Stream;
+import java.util.stream.IntStream;
+
+public class App{
+    public void main(String[] args){
+        Stream<Integer> stream = IntStream.range(0, 100).boxed();
+        $code
+        for(var item : result){
+            System.out.println(item);
+        }
+    }
+}
+```
+
+## 答案
+
+```java
+List<Integer> result = stream.map(x->x*2).collect(Collectors.toList());
+```
+
+## 选项
+
+### 没有变换为 List
+
+```java
+List<Integer> result = stream.map(x->x*2);
+```
+
+### lambda 格式错误
+
+```java
+List<Integer> result = stream.map(* 2).collect(Collectors.toList());
+```
+
+###  错误的使用了 foreach
+
+```java
+List<Integer> result = stream.foreach(item -> {
+    return item * 2
+});
+```
+

data/3.Java高阶/1.通过行为参数化传递代码/sum.json

+{
+  "type": "code_options",
+  "author": "刘鑫",
+  "source": "sum.md",
+  "notebook_enable": false
+}
\ No newline at end of file

data/3.Java高阶/1.通过行为参数化传递代码/sum.md

+# 求和
+
+下面代码对整数流求和，其中有错的是
+
+## 答案
+
+```java
+Stream<Integer> stream = IntStream.range(0,100).boxed();
+return stream.mapToInt(x -> x);
+```
+
+## 选项
+
+### 标准库方法
+
+```java
+Stream<Integer> stream = IntStream.range(0,100).boxed();
+return stream.sum();
+```
+
+### 显式调用 simmingInt 方法，可以定义一些复杂的处理逻辑
+
+```java
+var collector = Collectors.<Integer>summingInt(x->x);
+return stream.collect(collector);
+```
+
+### 也可以封装到一个朴素的方法中，作为隐式简写
+
+```java
+var collector = Collectors.<Integer>summingInt(this::identity);
+return stream.collect(collector);
+```
+
+### 也可以封装到一个朴素的方法中，作为隐式简写
+
+```java
+var collector = Collectors.<Integer>summingInt(App::identity);
+return stream.collect(collector);
+```
\ No newline at end of file

data/3.Java高阶/2.Lambda表达式/config.json

@@ -2,6 +2,9 @@
   "node_id": "java-a3b60740abe74bb8a6c16dec381d31c4",
   "keywords": [],
   "children": [],
-  "export": [],
+  "export": [
+    "lambda.json",
+    "sam.json"
+  ],
   "title": "Lambda表达式"
 }
\ No newline at end of file

data/3.Java高阶/2.Lambda表达式/handler.json

+{
+  "type": "code_options",
+  "author": "刘鑫",
+  "source": "handler.md",
+  "notebook_enable": false
+}
\ No newline at end of file

data/3.Java高阶/2.Lambda表达式/handler.md

+# 函数式的参数
+
+下面这个代码所定义的函数，用哪一种代码调用会出错？
+
+```java
+import java.util.function.Function;
+        
+public class App {
+    public <T, R> product(Function<T, R> consumer) {
+        // 这里有一段代码生成了 T value 变量 
+        return consumer(value);
+    }
+    // 省略其它代码
+}
+```
+
+## 答案
+
+```java
+Predicate<Float> checker = value -> {
+    return this.exp(value) < 1;
+}
+```
+
+## 选项
+
+### lambda 形式
+
+```java
+app.product(value -> {
+    return sigmod(value);
+});
+```
+
+### 对象方法
+
+```java
+app.product(this::sigmod)
+```
+
+### 类型方法
+
+```java
+app.product(App::sigmod)
+```
+
+### Function 对象
+
+```java
+Function<Float, Float> checker = value -> {
+    if(this.exp(value) < 1){
+        retrun 1/value;
+    } else {
+        return sigmod(value);
+    }
+}
+```
\ No newline at end of file

data/3.Java高阶/2.Lambda表达式/lambda.json

+{
+  "type": "code_options",
+  "author": "刘鑫",
+  "source": "lambda.md",
+  "notebook_enable": false
+}
\ No newline at end of file

data/3.Java高阶/2.Lambda表达式/lambda.md

+# Lambda 表达式
+
+下面这个 lambda 表达式，它的类型不可能是什么？ 
+
+```java
+x -> {
+    return x %2 == 0;
+}
+```
+
+## 答案
+
+```java
+Function<int, bool>
+```
+
+## 选项
+
+### 可以是 Function
+
+```java
+Function<Integer, Boolean>
+```
+
+### 可以是 Predicate
+
+```java
+Predicate<Integer>
+```
+
+### 可以是自定义的 SAM
+
+```java
+public interface Parsec{
+    Boolean ask(Integer value);
+}
+```
+
+### 可以是泛型的 SAM
+
+```java
+public interface Parsec<T, R>{
+    R ask(T value);
+}
+```