Góc học tập
23/01/2018 02:26:19 PM

Các câu hỏi phỏng vấn và câu trả lời về phần "Core Java - OOPs concepts: Initial OOPs" - Phần 2: Thuộc tính và phương thức tĩnh (static)

STATIC INTERVIEW QUESTIONS

1) What is static variable?

  • static variable is used to refer the common property of all objects (that is not unique for each object) e.g. company name of employees,college name of students etc.
  • static variable gets memory only once in class area at the time of class loading.

2) What is static method?

  • A static method belongs to the class rather than object of a class.
  • A static method can be invoked without the need for creating an instance of a class.
  • static method can access static data member and can change the value of it.

3) Why main method is static?

Because object is not required to call static method if It were non-static method,jvm creats object first then call main() method that will lead to the problem of extra memory allocation

4) What is static block?

  • Is used to initialize the static data member.
  • It is excuted before main method at the time of classloading.

5) Can we execute a program without main() method?

Yes, one of the way is static block

6) What if the static modifier is removed from the signature of the main method?

Program compiles. But at runtime throws an error "NoSuchMethodError".

7) What is difference between static (class) method and instance method?

static or class method

instance method

1)A method i.e. declared as static is known as static method.

A method i.e. not declared as static is known as instance method.

2)Object is not required to call static method.

Object is required to call instance methods.

3)Non-static (instance) members cannot be accessed in static context (static method, static block and static nested class) directly.

static and non-static variables both can be accessed in instance methods.

4)For example: public static int cube(int n){ return n*n*n;}

For example: public void msg(){...}.

 

» Các tin khác: