public class ReadWriteTextFile {
    
    private static ReadWriteTextFile rwt;
    public static ReadWriteTextFile getRWT(){
        if(null==rwt){
            rwt=new ReadWriteTextFile();
        }
        return rwt;
    }
}

------解决方案--------------------
Java code
public enum ReadWriteTextFile {
    Instance;
}

------解决方案--------------------
static {
 ....
}

这样就行了，何必非得需要时才new呢？我只关注结果。现在内存那么便宜。

------解决方案--------------------
单例模式应该是只返回一次一个类的实例   static静态块如何返回一个类的实例呢  因为不能把所有代码方法都写在静态块里吧

------解决方案--------------------
接分得

------解决方案--------------------
Java code
public class SingleTon {
    private static SingleTon singleTon = new SingleTon();
    private SingleTon(){};
    
    public static SingleTon getInstance() {
        return singleTon;
    }
}

------解决方案--------------------
Java code
class SingleTon2 {
    private static SingleTon2 singleTon;
    static {
        singleTon = new SingleTon2();
    }
    private SingleTon2(){};
    
    public static SingleTon2 getInstance() {
        return singleTon;
    }
}

------解决方案--------------------
Java code
class SingleTon3 {
    private static SingleTon3 singleTon3 = null;
    
    public synchronized SingleTon3 getInstance() {
        if (singleTon3 == null) {
            singleTon3 = new SingleTon3();
        }
        return singleTon3;
    }
    
}

------解决方案--------------------
if (instance == null) {
 synchronized (instance) {
   if (instance == null) {
     instance = new XXX();
   }
 }
}
return instance;

大概这么写  没写过  看人家差不多是这么写得

双重检查是啥。。。

------解决方案--------------------
探讨


Java code
public class ReadWriteTextFile {
    
    private static ReadWriteTextFile rwt;
    public static ReadWriteTextFile getRWT(){
        if(null==rwt){
            rwt=new ReadWriteTextFile()……


------解决方案--------------------
探讨


static {
  ....
}

这样就行了，何必非得需要时才new呢？我只关注结果。现在内存那么便宜。


------解决方案--------------------
synchronized  我不懂什么双重检查

------解决方案--------------------

╭︿︿︿╮  


------解决方案--------------------

A：单线程下单例模式；

Java code
public class Singleton {

    private static Singleton instance;

    private Singleton(){}

    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}