Java的23设计模式学习(课时一)单例模式

package coms.Design.Mode.single;
//静态内部类的定义
public class Hoder {
    //私有的方法
    private Hoder(){
    }
    public  static  Hoder getInstance(){
        return InnerClass.HODER;
    }
    public  static  class  InnerClass{
        private static  final Hoder HODER =new Hoder();
    }
    public static void main(String[] args) {
        Hoder hoder = new Hoder();
    }
}

package coms.Design.Mode.single;
public class LazyMan1 {
    private LazyMan1() {
        System.out.println(Thread.currentThread().getName()+"ok");
    }
    //volatile
    private  volatile  static LazyMan1 lazyMan;
    /**
     * 两重查看模式(Dcl)
     * @return
     */
    public static LazyMan1 getLazyMan() {
        if (lazyMan == null) {
            synchronized (LazyMan1.class) {
                if (lazyMan == null) {
                    lazyMan = new LazyMan1();
                }
            }
            //第二次查看
//        if(lazyMan==null){
//            lazyMan=new LazyMan();
//        }
        }
        //多线程
//    public static void main(String[] args) {
//        for (int i = 0; i < 10; i++) {
//            new Thread(()->{
//                lazyMan.getLazyMan();
//            }).start();
//        }
//    }
        return lazyMan;//此时lazyMan 还没有完成构造
    }
}

package coms.Design.Mode.single;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
/**
 * 道高一尺
 */
public class LazyMan {
    private  static  boolean we=false;
    private LazyMan() {
        synchronized (LazyMan.class){
            if(we==false){
                we=true;
            }else
                throw  new RuntimeException("不要破坏异常");
            }
//            if(lazyMan!=null){
//                throw  new RuntimeException("不要破坏异常");
//            }
        }
//        System.out.println(Thread.currentThread().getName()+"ok");
//    }
    //volatile
    private  volatile  static LazyMan lazyMan;
    /**
     * 两重查看模式(Dcl)
     * @return
     */
    public static LazyMan getLazyMan() {
        if (lazyMan == null) {
            synchronized (LazyMan.class) {
                if (lazyMan == null) {
                    lazyMan = new LazyMan();
                    /**
                     * 1 分配内存空间
                     * 2 执行构造方法
                     * 3 把这个对象指向这个空间
                     *
                     */
                }
            }
            //第二次查看
//        if(lazyMan==null){
//            lazyMan=new LazyMan();
//        }
        }
        //多线程
//    public static void main(String[] args) {
//        for (int i = 0; i < 10; i++) {
//            new Thread(()->{
//                lazyMan.getLazyMan();
//            }).start();
//        }
//    }
        return lazyMan;//此时lazyMan 还没有完成构造
    }
    //反射
    public static void main(String[] args) throws Exception {
//        LazyMan intance=LazyMan.getLazyMan();
        //私有的破坏
        Field we = LazyMan.class.getDeclaredField("we");
        we.setAccessible(true);
        Constructor<LazyMan> declaredConstructor = LazyMan.class.getDeclaredConstructor();
        //无视私有
        declaredConstructor.setAccessible(true);
        //俩个都是用了反射来new
        LazyMan intance=declaredConstructor.newInstance();
        we.set(intance,false);
        LazyMan intance2=declaredConstructor.newInstance();
        System.out.println(intance);
        System.out.println(intance2);
    }
}

package coms.Design.Mode.single;
import org.omg.CORBA.PUBLIC_MEMBER;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
//  是一个什么  本身也是一个类
public enum   EnumSingle {
    INSTANSINGLE;
    public  EnumSingle getInstansingle(){
        return INSTANSINGLE;
    }
}
/**
 * Exception in thread "main" java.lang.IllegalArgumentException: Cannot reflectively create enum objects
 *  at java.lang.reflect.Constructor.newInstance(Constructor.java:417)
 *  at coms.Design.Mode.single.Test.main(EnumSingle.java:22)
 *
 *  没据 不能 破坏 单例
 */
class Test{
    public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        EnumSingle instanSingle1 =EnumSingle.INSTANSINGLE;
        Constructor<EnumSingle> declaredConstructor = EnumSingle.class.getDeclaredConstructor(String.class,int.class);
        declaredConstructor.setAccessible(true);
        EnumSingle instanSingle2 = declaredConstructor.newInstance();
        //没有空参构造
        System.out.println(instanSingle1);
        System.out.println(instanSingle2);
    }
}