jdk learn

.idea/misc.xml

@@ -3,7 +3,7 @@
   <component name="ProjectKey">
     <option name="state" value="project://e2804f05-5315-4fc6-a121-c522a6c26470" />
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="17" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="17" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file

src/com/newJDK/jdk10/VarLearn.java

+package com.newJDK.jdk10;
+
+import java.util.List;
+
+/**
+ * 10  var  学习
+ * @author lx
+ * @date 2021/11/30 16:41
+ * https://mp.weixin.qq.com/s/6yBUSfDCP_cqJAm0uRBFvQ
+ **/
+public class VarLearn {
+    public static void main(String[] args) {
+
+    }
+
+
+    public static void var(){
+        var a = "555";
+        System.err.println(a.getClass().getTypeName());
+    }
+}

src/com/newJDK/jdk9/OptionalLearn.java

+package com.newJDK.jdk9;
+
+import java.util.Optional;
+
+/**
+ * 9 对于 Optional 的学习
+ *
+ * @author lx
+ * @date 2021/11/30 14:31
+ **/
+public class OptionalLearn {
+
+    public static void main(String[] args) {
+        System.out.println(ProcessHandle.current().pid());
+        System.out.println(ProcessHandle.current().info());
+    }
+
+    public static void isEmptyIsPresent() {
+        // Optional.ofNullable(null);  == Optional.empty();
+        Optional<Object> empty = Optional.empty();
+        // 非空 = true      空  = false
+        System.out.println(empty.isPresent());
+        // 空  = true
+        System.out.println(empty.isEmpty());
+
+        Optional<String> s = Optional.ofNullable("5");
+        System.out.println(s.isPresent());
+        System.out.println(s.isEmpty());
+    }
+
+
+    public static void ifPresentOrElse() {
+        Optional<String> s = Optional.ofNullable(null);
+        //空 就不执行
+        s.ifPresent(System.out::println);
+        //空不空在方法内区分
+        s.ifPresentOrElse(
+                y -> System.out.println("不是空的" + y),
+                () -> System.out.println("空的")
+        );
+    }
+
+    public static void or() {
+        Optional<Object> s = Optional.ofNullable("4444");
+
+        // s空的 就返回else里面的，s非空就返回s的值
+        Object s1 = s.orElse("6");
+        System.err.println(s1);
+
+        // s空的 就验证or是不是空的， s非空就返回
+        Optional<Object> or = s.or(() -> Optional.ofNullable("5555"));
+        System.err.println(or.get());
+    }
+}

src/com/newJDK/jdk9/StreamLearn.java

+package com.newJDK.jdk9;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+/**
+ * 9 对于 stream 流的学习
+ * @author lx
+ * @date 2021/11/30 14:31
+ **/
+public class StreamLearn {
+
+    public static void takeWhile(){
+        // 依次寻找直至不符合条件，找到一个向下传递一个
+        List<Integer> integerList = List.of(11, 33, 66, 8, 9, 13);
+        integerList.stream().takeWhile(x -> x < 50).forEach(System.out::println);
+    }
+
+    public static void dropWhile(){
+        // 依次寻找直至不符合条件，找打一个删除一个，剩下的向下传递
+        List<Integer> integerList = List.of(11, 33, 66, 8, 9, 13);
+        integerList.stream().takeWhile(x -> x < 50).forEach(System.out::println);
+    }
+
+    public static void iterate(){
+        // 使用原始 iterate() 方法输出数字 1~10
+        Stream.iterate(1, i -> i + 1).limit(10).forEach(System.out::println);
+
+        // 使用新的 iterate() 重载方法输出数字 1~10
+        Stream.iterate(1, i -> i <= 10, i -> i + 1).forEach(System.out::println);
+    }
+
+
+}

src/com/pattern/PatternApplication.java

@@ -3,11 +3,21 @@ package com.pattern;
 import com.pattern.BuilderPattern.materials.BuilderMain;
 import com.pattern.CompositePattern.materials.CompositeMain;
 
+import java.io.Serializable;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
 /**
  * @author lx
  */
 public class PatternApplication {
 
+    /**
+     * 请确保您的JDK版本是最新版本哦   jdk.17
+     *
+     * @param args main
+     */
     public static void main(String[] args) {
 
         /*
@@ -106,11 +116,24 @@ public class PatternApplication {
          */
 
 
-        new CompositeMain().main();
         /*
         12.组合模式
+        new CompositeMain().main();
         2021-11-25:一个实体包含了小规模业务
          */
+
+
+        List<String> list = List.of("x", "www", "yy", "zz");
+        Map<Integer, List<String>> result = list.stream()
+                .collect(Collectors.groupingBy(
+                        String::length,
+                        Collectors.filtering(
+                                s -> s.contains("z"),
+                                Collectors.toList())
+                        )
+                );
+
+        System.err.println(result.toString());
     }
 
 }