java 学习泛型遇到的问题

泛型的子类继承问题：

泛型子类无法赋值给其泛型父类

package agenericity;class Info<T> {private T var;public T getVar() {return var;}public void setVar(T var) {this.var = var;}}public class GenericityTest {public static void main(String[] args) {Info<String> ln = new Info<String>();Info<Object> ol = null;ol = ln;}}

错误提示：Type mismatch: cannot convert from Info<String> to Info<Object>