1.懒汉式

public class jetlag{

        private static Jetlag jetllag = null;

        priavte Jetlag(){}

         private static Jetlag getJetlag(Jetlag jetllag){

            if(jetllag == null){

                    jetlag = new Jetlag();

}

return jetlag;

}

}

2.饿汉式

public class Jetlag{

        private static Jetlag  jetlag= new Jetlag();

        private Jetlag(){}

        public static Jetlag(){

        return jetlag;

}

}

3.变种的饿汉式

public class Jetlag{

private statci Jetlag jetlag = null;

static {    

jetlag = new Jetlag();

}

private Jetlag(){}

public static Jetlag(){

return this.jetlag;

}

}