list map初始化是否需要赋值

public class test {
    public static void main(String[] args) {
        List a  = new ArrayList();
        System.out.println(a.toString());
//        System.out.println(a.get(0)); //报错空指针

        Map m = new HashMap();
        System.out.println(m.toString());
        System.out.println(m.get(0)); //正常，不报错

    }
}