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‎01jvm/out/production/01jvm/README.md‎

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@@ -113,6 +113,36 @@ java -Xmx2g -Xms2g -XX:+UseG1GC -verbose:gc -XX:+PrintGCDateStamps -XX:+PrintGCD
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其中 [GCLogAnalysis.java](./GCLogAnalysis.java) 文件也可以从课件资料zip中找到.
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## 几个命令用法
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### 1、十六进制方式查看文件
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`hexdump -C Hello.class`
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输出：`00000000 ca fe ba be 00 00 00 34 00 1c 0a 00 06 00 0e 09`
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可以看到magic number： `cafe babe`，
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以及`00 00 00 34`，十六进制34=十进制3*16+4=52，这是jdk8，如果是jdk11则是55，十六进制37.
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### 2、Base64方式编码文件
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`base64 Hello.class`
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### 3、显示JVM默认参数
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```
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java -XX:+PrintFlagsFinal -version
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java -XX:+PrintFlagsFinal -version | grep -F " Use" | grep -F "GC "
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java -XX:+PrintFlagsFinal -version | grep MaxNewSize
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```
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### 4、切换不同jdk
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```
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jenv shell 1.8
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jenv shell 11
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```
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显示所有jdk
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```
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jenv versions
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```
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## 更多资料
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更多中英文的技术文章和参考资料: <https://github.com/cncounter/translation>

‎01jvm/subinterface/Mapper.java‎

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package subinterface;
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public interface Mapper<T> {
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void insert(T t);
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}

‎01jvm/subinterface/User.java‎

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package subinterface;
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public class User {
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private int id;
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public User(int id) {
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this.id = id;
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}
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public int getId() {
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return id;
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}
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public void setId(int id) {
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this.id = id;
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}
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}

‎01jvm/subinterface/UserDAO.java‎

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package subinterface;
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public class UserDAO implements UserMapper {
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@Override
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public void insert(User user) {
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System.out.println("Insert user id: " + user.getId());
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}
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}

‎01jvm/subinterface/UserMain.java‎

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package subinterface;
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public class UserMain {
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public static void main(String[] args) {
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UserDAO dao = new UserDAO();
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dao.insert(new User(123));
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}
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}

‎01jvm/subinterface/UserMapper.java‎

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package subinterface;
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public interface UserMapper extends Mapper<User> {
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@Override
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void insert(User user);
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}

‎04fx/java8/src/main/java/io/kimmking/java8/ResourceLoader.java‎

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package io.kimmking.java8;
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import lombok.SneakyThrows;
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import java.io.BufferedReader;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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public class ResourceLoader {
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static String file = "conf/a.properties";
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public static void main(String[] args) {
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// testClassLoaderRootPath(); // classloader方式不能加根路径，否则文件路径会直接被替换掉最终成了 /conf/a.properties
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testClassLoader(); // 从当前的classpath，不管是 文件夹，还是jar里去找 资源
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testClassRootPath(); // 判断第一个字符是根路径，去掉根，转成 testClassLoader 调用
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// testClass(); // class 方式必须加根路径，不加根会根据类路径io.kimmking.java8.ResourceLoader 去拼成 io/kimmking/java8/conf/a.properties
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}
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private static void testClassLoader() {
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System.out.println("====> testClassLoader");
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loadStream(ResourceLoader.class.getClassLoader().getResourceAsStream(file));
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}
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private static void testClassLoaderRootPath() {
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System.out.println("====> testClassLoader");
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loadStream(ResourceLoader.class.getClassLoader().getResourceAsStream("/"+file));
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}
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private static void testClass() {
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System.out.println("====> testClass");
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loadStream(ResourceLoader.class.getResourceAsStream(file));
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}
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private static void testClassRootPath() {
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System.out.println("====> testClassRootPath");
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loadStream(ResourceLoader.class.getResourceAsStream("/"+file));
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}
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@SneakyThrows
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private static void loadStream(InputStream in) {
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BufferedReader reader = new BufferedReader(new InputStreamReader(in));
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StringBuffer buffer = new StringBuffer();
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String line = null;
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while ((line = reader.readLine()) != null) {
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buffer.append(line);
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}
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System.out.println(buffer.toString());
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reader.close();
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in.close();
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}
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}

‎04fx/java8/src/main/resources/conf/a.properties‎

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a=1
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b=2

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