Nowcoder (5 choices)

 

1、 Which of the following is the advantage of array over linked list ？

• right key : D   

A  Convenient deletion 

B  Convenient insertion 

C  Variable length 

D  Small storage space 

analysis ：

1： The memory space of array is less than that of linked list .

2： Array supports random access , Linked list does not have the property of random access .

3： Insert and delete are linked lists better than arrays , The array needs to move the element after the deleted or inserted position .

2、 Array  A[0…5 , 0…6]  Each element of accounts for  5  Bytes , Store it in column priority at the starting address of  1000  In the memory unit of , The element  A[5 , 5]  The address for ？

• right key A

 

A 1175

B 1180

C 1205

D 1210

analysis ：

1： Note that it is stored by column . So the address should be ： ( Line length * ( Column - 1) + Place of action - 1) * Unit length + Initial address (6 * (6 - 1) + 6 - 1) * 5 + 1000 = 1175 It's about replacing , The row is the position of the element in the row or column .

2：a[5][5] It's No 6 Xing di 6 Elements （ Subscript from 0 At the beginning ） The row and column are 6. Don't remember the formula , The first 6 Xing di 6 Elements are stored in columns, with 5 Columns complete columns , Add the number 6 There is 5 Elements . So there are 6 * (6 - 1) + 6 - 1 Elements .

3、10. class Line {
11. public class Point { public int x,y;}
12. public Point getPoint() { return new Point(); }
13. }
14. class Triangle {
15. public Triangle() {
16. // insert code here
17. }
18. }
In the 16 Line insert which code can get a Point Coordinates of objects ?(  )

• right key D

A Point p = Line.getPoint();

B Line.Point p = Line.getPoint();

C Point p = (new Line()).getPoint();

D Line.Point p = (new Line()).getPoint();

analysis ：

1： Define another class in the class , Call it an inner class .

2： In the inner class , You can access the properties and methods of internal classes at any time , But external classes need to create objects to access .

3： The classification of internal classes are 1 Member inner class 2 Local inner classes 3 Anonymous inner class

4： Member internal class access rules
Member inner class is not static ：
External class name . Internal class name Object name = new External class name ().new Internal class name ();
Member inner classes are static ：

External class name . Internal class name Object name = new External class name . Internal class name ();

5： Local inner classes
A: Local internal classes must add... To access local variables final modification .
B: Why? ?
Because local variables disappear when they are used , And the data in the heap doesn't immediately disappear .
therefore , Heap memory still uses this variable , And the change variable is gone .
In order for the value to still exist , Just add final modification .
Through the decompilation tool, we see , Join in final after , Heap memory stores values directly , Not variable names .
:6： Anonymous inner class ( master )
A: Is a simplified form of a local inner class
B: Premise
There is a class or interface
C: Format :
new Class name or interface name () {
Rewriting methods ;
}
D: The essence ： In fact, it is an anonymous object that inherits the class or implements the interface .

4、 What modifiers can local inner classes use to decorate ？

• right key ：CD

A public

B private

C abstract

D final

This picture is made by others , It is of great help to this problem .

5、 In the length of n Of the sequence table i（1≤i≤n+1） Insert an element at a location , The number of moves of the element is ？

• right key A

A n-i+1

B n-i

C i

D i-1

analysis ：

Because in i Insert an element at , That is to say, the original linked list i Position plus all elements behind yourself move back once , That is to say n+1-i Time .