集合框架——定义泛型类

/*class Tool{private Worker w;public void setWorker(Worker w){this.w = w;}public Worker getWorker(){return w;}}*/class Worker{}class Student{}//泛型前做法。class Tool{private Object obj;public void setObject(Object obj){this.obj = obj;}public Object getObject(){return obj;}}//泛型类。/*什么时候定义泛型类？当类中要操作的引用数据类型不确定的时候，早期定义Object来完成扩展。现在定义泛型来完成扩展。*/class Utils<QQ>{private QQ q;public void setObject(QQ q){this.q = q;}public QQ getObject(){return q;}}class  GenericDemo3{public static void main(String[] args) {Utils<Worker> u = new Utils<Worker>();u.setObject(new Student());Worker w = u.getObject();;/*Tool t = new Tool();t.setObject(new Student());Worker w = (Worker)t.getObject();*/}}