feat

Author: CodePrometheus

JMM/src/singleton/lazyman/SingletonEnum.java

@@ -1,5 +1,8 @@
 package singleton.lazyman;
 
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+
 /**
  * 单例之八 -> 枚举（生产实践推荐使用）
  * -> 单元素的枚举类型已经成为实现Singleton的最佳方法
@@ -12,7 +15,30 @@ public enum SingletonEnum {
 
     INSTANCE;
 
-    public void whatever() {
+    public SingletonEnum getInstance() {
+        return INSTANCE;
+    }
 
+    /**
+     * 检查反射攻击
+     *
+     * @param args
+     */
+    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {
+        SingletonEnum singleton1 = SingletonEnum.INSTANCE;
+        SingletonEnum singleton2 = SingletonEnum.INSTANCE;
+        System.out.println("正常情况下，实例化两个实例是否相同：" + (singleton1 == singleton2));
+        Constructor<SingletonEnum> constructor;
+        // 一旦一个类声明为枚举，实际上就是继承了 Enum，所以会有（String.class,int.class）的构造器
+        constructor = SingletonEnum.class.getDeclaredConstructor(String.class, int.class); // 其父类的构造器
+        constructor.setAccessible(true);
+        SingletonEnum singleton3;
+        singleton3 = constructor.newInstance("testInstance", 66);
+        System.out.println(singleton1 + "\n" + singleton2 + "\n" + singleton3);
+        /**
+         * if ((clazz.getModifiers() & Modifier.ENUM) != 0)
+         *             throw new IllegalArgumentException("Cannot reflectively create enum objects");
+         */
+        System.out.println("通过反射攻击单例模式情况下，实例化两个实例是否相同：" + (singleton1 == singleton3));
     }
 }

Thread/src/importantmethod/waitnotify/WaitNotifyReleaseOwnMonitor.java

@@ -11,7 +11,7 @@ public class WaitNotifyReleaseOwnMonitor {
     private static volatile Object resource2 = new Object();
 
     public static void main(String[] args) {
-        var thread1 = new Thread(() -> {
+        Thread thread1 = new Thread(() -> {
             synchronized (resource1) {
                 System.out.println("Thread1 got resource1 lock");
                 synchronized (resource2) {