饿汉模式

//饿汉模式class Bank{    private Bank(){         }    private static Bank bank = new Bank();        public static Bank hugger(){        return bank;    }}

懒汉模式

class Bank1{    private Bank1(){            }    private static Bank1 bank = null;        public static  Bank1 lazse(){                if(bank == null){            synchronized(Bank1.class){                if(bank == null){                    bank = new Bank1();                }            }        }        return bank;    }