Java 14 更新

Author: BestBurning

README.md

@@ -109,11 +109,14 @@
 - ZGC 增强 - 释放未使用内存
 - SocketAPI 重构
 
-### JDK 14
+### [JDK 14](java-14)
 
 ---
 
-- instanceof模式识别
-- Records
-- 启用Parallel Scavenge+Serial GC组合
-- 删除CMS GC
+- [instanceof模式识别 增强](java-14/src/main/java/com/di1shuai/java14/instance/InstanceOfDemo.java)
+- [Record 类型](java-14/src/main/java/com/di1shuai/java14/record/RecordDemo.java)
+- [异常信息提示改进](java-14/src/main/java/com/di1shuai/java14/nullexception/NullPointerExceptionDemo.java)
+- 其他 
+  - G1 的 NUMA 可识别内存分配
+  - 删除 CMS GC
+  - GC 支持 MacOS 和 Windows 系统

java-14/README.md

@@ -0,0 +1,11 @@
+### JDK 14
+
+---
+
+- [instanceof模式识别 增强](src/main/java/com/di1shuai/java14/instance/InstanceOfDemo.java)
+- [Record 类型](src/main/java/com/di1shuai/java14/record/RecordDemo.java)
+- [异常信息提示改进](src/main/java/com/di1shuai/java14/nullexception/NullPointerExceptionDemo.java)
+- 其他
+    - G1 的 NUMA 可识别内存分配
+    - 删除 CMS GC
+    - GC 支持 MacOS 和 Windows 系统

java-14/pom.xml

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>java-versions</artifactId>
+        <groupId>com.di1shuai</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>java-14</artifactId>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>15</source>
+                    <target>15</target>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>14</maven.compiler.source>
+        <maven.compiler.target>14</maven.compiler.target>
+    </properties>
+
+</project>

java-14/src/main/java/com/di1shuai/java14/instance/InstanceOfDemo.java

@@ -0,0 +1,25 @@
+package com.di1shuai.java14.instance;
+
+/**
+ * @author Shea
+ * @date 2021-01-22
+ * @description
+ */
+public class InstanceOfDemo {
+
+    public static void main(String[] args) {
+        Object obj = "  hello Java 14  ";
+        // < 14
+        if (obj instanceof String) {
+            System.out.println(((String) obj).strip());
+        }
+
+        // 14
+        if (obj instanceof String str) {
+            System.out.println(str.strip());
+        }
+
+
+    }
+
+}

java-14/src/main/java/com/di1shuai/java14/nullexception/NullPointerExceptionDemo.java

@@ -0,0 +1,32 @@
+package com.di1shuai.java14.nullexception;
+
+/**
+ * @author Shea
+ * @date 2021-01-23
+ * @description
+ *
+ *  before 14
+ *
+ * java.lang.NullPointerException
+ * 	at com.di1shuai.java14.nullexception.NullPointerExceptionDemo.main(NullPointerExceptionDemo.java:21)
+ *
+ *
+ *  14 默认开启 -XX:+ShowCodeDetailsInExceptionMessages
+ *
+ * Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.toString()" because "str" is null
+ * 	at com.di1shuai.java14.nullexception.NullPointerExceptionDemo.main(NullPointerExceptionDemo.java:12)
+ *
+ */
+public class NullPointerExceptionDemo {
+
+    public static void main(String[] args) {
+        String str = null;
+        try {
+            str.toString();
+        }catch (NullPointerException e){
+            e.printStackTrace();
+        }
+
+    }
+
+}

java-14/src/main/java/com/di1shuai/java14/record/RecordDemo.java

@@ -0,0 +1,41 @@
+package com.di1shuai.java14.record;
+
+/**
+ * @author Shea
+ * @date 2021-01-22
+ * @description
+ *
+ *
+ */
+public class RecordDemo{
+
+    public static void main(String[] args) {
+        Student s = new Student("shea",18);
+        System.out.println(
+                """
+                getName  -> %s        
+                getAge   -> %s
+                toString -> %s
+                hashCode -> %s        
+                """.formatted(
+                        s.name(),
+                        s.age(),
+                        s.toString(),
+                        s.hashCode()
+                )
+        );
+    }
+
+
+}
+
+/**
+ * 构造方法
+ * hashCode() 方法
+ * euqals() 方法
+ * toString() 方法
+ * 类对象被final 关键字修饰，不能被继承。
+ */
+record Student(String name,int age){
+
+}

pom.xml

@@ -18,6 +18,7 @@
         <module>java-10</module>
         <module>java-12</module>
         <module>java-13</module>
+        <module>java-14</module>
     </modules>
 
     <dependencyManagement>