class Single
{
private Single(){}
private static Single s = null;
public static Single getInstance(){
if(s == null){
synchronized(Single.class){
if(s == null){
s = new Single();
}
}
}
return s;
}
}
public class Single{
//私有化构造器
private Sigle(){
}
//用一个静态内部类holder一个静态成员。
private static class SingleHolder{
private static Single instance =
new Single();
}
public Single getInstance(){
return SingleHolder.instance;
}
}