向上转型把一个子类类型安全的的变为父类类型的赋值，称为向上转型。eg：Student s= new Student(); Person p=s;向下转型把一个父类类型强制转型为子类类型，就是向下转型Person p1 = new Student(); // upcasting, okPerson p2 = new Person();Student s1 = (Student) p1; // okStudent s2 = (Student) p2; // runtime error! C
java
2024-01-12
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