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类Teacher和Student是类Person的子类;     Person p;     Teacher t;     Student s;     //p, t and s are all non-null.     if(t instanceof Person) { s = (Student)t; }   最后一句语句的结果是:()

A.将构造一个Student对象;

B.表达式是合法的;

C.表达式是错误的;

D.编译时正确,但运行时错误。


参考答案和解析
表达式是错误的
更多 “类Teacher和Student是类Person的子类;     Person p;     Teacher t;     Student s;     //p, t and s are all non-null.     if(t instanceof Person) { s = (Student)t; }   最后一句语句的结果是:()A.将构造一个Student对象;B.表达式是合法的;C.表达式是错误的;D.编译时正确,但运行时错误。” 相关考题
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