\`\`\`java import java.io.Serializable; // 修改后的单例模式 // 使用线程同步创建，防止进程切换重复创建线程， // 设置volatile关键字修饰，使读取singleton对象时能够获取最新状态 // 修改构造方法，防止反射创建对象 // 修改readResolve方法，防止反序列化对象时重新创建对象 // 重写克隆方法，防止对象克隆 public class Singleton2 implements Serializable, Cloneable { private static volatile Singleton2 singleton; private Singleton2() { if (singleton != null) { throw new RuntimeException("对象已被创建"); } } public static Singleton2 getInstance() { if (singleton == null) { synchronized (singleton) { if (singleton == null) singleton = new Singleton2(); } } return singleton; } private Object readResolve() { return singleton; } @Override protected Object clone() throws CloneNotSupportedException { return getInstance(); } } \`\`\` \`\`\`java // 还可以创建 Constructor con = Singleton2.class.getDeclaredConstructor(null); con.setAccessible(true); Singleton2 s1 = con.newInstance(); Singleton2 s2 = con.newInstance(); System.out.println(s1); System.out.println(s2); \`\`\` \`\`\`java // 枚举方式,可以完全防止反射 enum Singleton2 implements Serializable,Cloneable{ Singleton2; public Singleton2 getInstance(){ return Singleton2; } } \`\`\`