public class singleton {
private static singleton instance =new singleton();
private singleton(){
}
public static singleton getInstance(){
return instance;
}
}
class singleton2{
private static singleton2 s;
private singleton2(){
}
public static synchronized singleton2 getInstance(){
if(s==null){
s=new singleton2();
}
return s;
}
}
class singleton3{
private static class singletoninstance{
private static final singleton3 instance =new singleton3();
}
public static singleton3 getInstance(){
return singletoninstance.instance;
}
private singleton3(){}
}
enum singleton4{
INSTANCE;
}