2 代码演练
2 代码演练
2.1 代码演练
package com.geely.design.pattern.creational.singleton; import java.io.*; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; public class Test { /*public static void main(String [] args){ //这样写异常,因为构造方法私有 // LazySingleton lazySingleton = new LazySingleton(); LazySingleton lazySingleton = LazySingleton.getInstance(); System.out.println(lazySingleton); }*/ /* public static void main(String [] args){ Thread thread1 = new Thread(new T()); Thread thread2 = new Thread(new T()); thread1.start(); thread2.start(); System.out.println("结束了!!!"); }*/ /** * 序列化代码演练 * 将 HungrySingleton对象放入文件,再从文件读取该对象,还是同一个对象吗? * 实际应用:在从文件存入后读取,用equals时需要注意(equals比较的是hash码) * @param args */ public static void main(String [] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException { /* try { //将singleton对象写入到输出流中 HangrySingleton instance = HangrySingleton.getInstance(); ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("singleton_file")); oos.writeObject(instance); //从输入流中读取到该对象 File file = new File("singleton_file"); ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file)); HangrySingleton instance2 = (HangrySingleton) ois.readObject(); System.out.println(instance); System.out.println(instance2); System.out.println(instance==instance2); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } */ //反射攻击 Class objectClass = HangrySingleton.class; // Class.forName(HangrySingleton.class.getName()); //通过反射拿到构造器 Constructor constructor = objectClass.getDeclaredConstructor(); //设置权限为true,不设置的话,私有权限反射报错 constructor.setAccessible(true); //通过单例拿到对象 HangrySingleton instance = HangrySingleton.getInstance(); //通过反射拿到对象 HangrySingleton instance2 = (HangrySingleton)constructor.newInstance(); System.out.println(instance); System.out.println(instance2); System.out.println(instance==instance2); } }
打印日志:
"C:\Program Files\Java\jdk1.7.0_79\bin\java.exe" "-javaagent:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar=27494:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.7.0_79\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jce.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfxrt.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\resources.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\design_pattern\target\classes" com.geely.design.pattern.creational.singleton.Test com.geely.design.pattern.creational.singleton.HangrySingleton@6cff7cd8 com.geely.design.pattern.creational.singleton.HangrySingleton@795d80cf false Process finished with exit code 0