代码训练营——泛型实例

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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;
    }
}

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class GenericDemo3
{
    public static void main(String[] args)
    {
        Tool t = new Tool();
        t.setObject(new Student());
        Student stu = (Student)t.getObject();
    }
}

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Tool t = new Tool();
t.setObject(new Student());
Worker work = (Worker)t.getObject();

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Exception in thread "main" java.lang.ClassCastException: Student cannot be cast to Worker

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//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<Temp>
{
    private Temp t;
    public void setObject(Temp t)
    {
        this.t = t;
    }
    public Temp getObject()
    {
        return t;
    }
}
class GenericDemo3
{
    public static void main(String[] args)
    {
        Utils<Worker> u = new Utils<Worker>();
        u.setObject(new Worker());
        Worker w = u.getObject();
    }
}

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Utils<Worker> u = new Utils<Worker>();
u.setObject(new Student());
Worker w = u.getObject();