optional

data/3.Java高阶/1.行为抽象和Lambda/6.分区/config.json

@@ -2,5 +2,5 @@
   "node_id": "java-05498c81f6be42a2a44ddb4de0178420",
   "keywords": [],
   "children": [],
-  "export": []
+  "export": ["partition_by.json"]
 }
\ No newline at end of file

data/3.Java高阶/1.行为抽象和Lambda/6.分区/partition_by.json

+{
+  "type": "code_options",
+  "author": "刘鑫",
+  "source": "partition_by.md",
+  "notebook_enable": false,
+  "exercise_id": "0fdf50ac2303468090d036e7fc0ee726"
+}
\ No newline at end of file

data/3.Java高阶/1.行为抽象和Lambda/6.分区/partition_by.md

+# 二分
+
+现有一个数据流 `Stream<Integer> stream`， 下列代码尝试把它按正负号分为两部分（不拘于某种结果类型，能够区分两类数据即可），其中有错的是？
+
+## 答案
+
+```java
+Stream<Integer> upstream=stream.filter(x->x>=0);
+Stream<Integer> downstream=stream.filter(x->x< 0);
+```
+
+## 选项
+
+### 常规方法
+
+```java
+Collectors.partitionBy(x->x>=0,stream);
+```
+
+### 常规方法
+
+```java
+Collector<Integer, ?, Map<Boolean, List<Integer>>>collector=Collectors.partitioningBy(x->x>0);
+stream.collect(collector);
+```
+
+### 朴素方法
+
+```java
+List<Integer> upstream=new ArrayList<>();
+List<Integer> downstream=new ArrayList<>();
+
+stream.foreach(x->{
+    if(x>=0){
+        upstream.add(x);
+    }else{
+        downstream.add(x);
+    }
+})
+```
\ No newline at end of file

data/3.Java高阶/2.Optional/1.Optional与Null/config.json

+{
+  "node_id": "java-36a3b51a36624ee8930794d64da6b22a",
+  "keywords": [],
+  "children": [],
+  "export": ["optional.json"]
+}
\ No newline at end of file

data/3.Java高阶/3.Optional/optional.json → data/3.Java高阶/2.Optional/1.Optional与Null/optional.json

@@ -2,5 +2,6 @@
   "type": "code_options",
   "author": "刘鑫",
   "source": "form.md",
-  "notebook_enable": false
+  "notebook_enable": false,
+  "export": ["optional.json"]
 }
\ No newline at end of file

data/3.Java高阶/2.Optional/1.Optional与Null/optional.md

+# Optional 应用
+
+现有一个 `String content` 字符串，它有可能是 NULL ，也有可能是字符串，那么下列将其转为 Optional 的操作，哪个是错的？
+
+## 答案
+
+```java
+var opt = Optional.of(content);
+```
+
+## 选项
+
+### 常规方法
+
+```java
+var opt = Optional.ofNullable(content);
+```
+
+### 平凡方法，不推荐，但可用
+
+```java
+Optional<String> opt;
+if(content == null){
+    opt = Optional.empty();
+} else {
+    opt = Optional.of(content);
+}
+```
+
+### C
+
+以上全都可用，没有错误代码

data/3.Java高阶/2.Optional/2.一致性/config.json

+{
+  "node_id": "java-6a0ad22b08cd4520b453904d832936ea",
+  "keywords": [],
+  "children": [],
+  "export": ["optional.json"]
+}
\ No newline at end of file

data/3.Java高阶/2.Optional/2.一致性/optional.json

+{
+  "type": "code_options",
+  "author": "刘鑫",
+  "source": "form.md",
+  "notebook_enable": false,
+  "export": ["optional.json"]
+}
\ No newline at end of file

data/3.Java高阶/3.Optional/config.json → data/3.Java高阶/2.Optional/config.json

@@ -2,6 +2,5 @@
   "node_id": "java-c3a2ef586dd7449788102b631419992f",
   "keywords": [],
   "children": [],
-  "export": ["optional.json"],
-  "title": "用Optional取代null"
+  "export": []
 }
\ No newline at end of file

data/tree.json

@@ -2756,7 +2756,9 @@
                   {
                     "类型转换前先做检查": {
                       "node_id": "java-48593d705752415e95c42b09d36bc2a4",
-                      "keywords": [],
+                      "keywords": [
+                        "instanceof"
+                      ],
                       "children": [
                         {
                           "使用类字面常量": {
@@ -2802,7 +2804,9 @@
                   {
                     "反射：运行时类信息": {
                       "node_id": "java-42b26ca8a2384dcfb02fca6e159ace67",
-                      "keywords": [],
+                      "keywords": [
+                        "annotation"
+                      ],
                       "children": [
                         {
                           "类方法抽取器": {
@@ -4009,9 +4013,6 @@
                       "keywords": [],
                       "children": []
                     }
-                  }
-                ]
-              }
                   },
                   {
                     "分区": {
@@ -4019,14 +4020,32 @@
                       "keywords": [],
                       "children": []
                     }
+                  }
+                ]
+              }
             },
             {
               "Optional": {
                 "node_id": "java-c3a2ef586dd7449788102b631419992f",
                 "keywords": [],
+                "children": [
+                  {
+                    "Optional与Null": {
+                      "node_id": "java-36a3b51a36624ee8930794d64da6b22a",
+                      "keywords": [],
                       "children": []
                     }
                   },
+                  {
+                    "一致性": {
+                      "node_id": "java-6a0ad22b08cd4520b453904d832936ea",
+                      "keywords": [],
+                      "children": []
+                    }
+                  }
+                ]
+              }
+            },
             {
               "Java模块系统": {
                 "node_id": "java-81c079af472746fc838268974b43dc55",