单例里面怎么设计一个map对象！真心求代码

package test;import java.util.HashMap;import java.util.Map;public class SingleTon {    private Map<Object,Object> map;        private static SingleTon singleTon;        private SingleTon(){        map = new HashMap<Object,Object>();    }        public static SingleTon getSingleTon(){        if(singleTon == null){            singleTon = new SingleTon();        }        return singleTon;    }        public void put(Object key, Object value){        map.put(key, value);    }        public Object get(Object key){        return map.get(key);    }}