chapter 3 -revisited

Question 1

what is a class?

Answer 1

blueprint of an object

defines the variables and methods an object contains.

Question 2

what are the parts of the following line of code (class, etc):
Scanner scan = new Scanner(System.in);

Answer 2

Scanner scan = new Scanner(System.in);
__________________________________
Scanner – is the class and the blue print for objects.
scan – is an object being created/
new – is a java operator that is the creator of a new object.
Scanner – this is a constructor and part of the Scanner class.
( )— used after the Scanner as part of its constructor to set the parameters that must be used.
(System.in) — parameters used represents input from the keyboard.

Question 3

if i wanted to create a second scanner object with the same functionality as the first then how would i and what is this called?

Answer 3

Scanner scan2;
^ is a deceleration in itself.
scan2 = scan;
^^ both are the same in functionality.
Aliases of one another: 2 ways to get to the same object.
“when multiple reference variables refer to the same object”.

Question 4

if i wanted to create a second scanner object but have it scan from a different input such as a file then how would i do this?

Answer 4

scan2 = new Scanner(new File ("myData.txt"));
here a new object called scan2 is created and it uses the constructor with parameters that scans in data from a specific file.

Question 5

what is a constructor?

Answer 5

constructor:

a method that sets up a newly created object used to give an initial value to a variable.

Question 6

how to create a random object for generation of random numbers? (random class)

Answer 6

Random generating = new Random();
generating is the object name that we set for random
import java.util.random;

Question 7

int num1 = generating.nextInt(300);

what will this do?

Answer 7

will return a random number in the range between 0 and 299.

Question 8

what code is written to create a random number between 0 and 6?

Answer 8

int num2 = generating.nextINT(5) + 1;

Question 9

what range will the following code give me?

int num3 = generating.nextInt(20) - 10;

Answer 9

int num3 = generating.nextInt(20) - 10;
will produce a range of: -10 and 9
**the (20) produces a range of 0 through 19 then we add the -10 for the final range.

Question 10

are math class methods static or do we use objects to invoke methods of the math class?

Answer 10

math class methods are static.
so what this means:
int num4 = Math.cos(30);
                        ^^ this object was not created by me b/c it is static with the math class and already made.

Question 11

what is the math function to raise a number to a power?

Answer 11

int squared = Math.pow(a, 2);

^ object name ^ a represents the number while 2 represents the exponent (power being raised to)

Question 12

The math function uses what type of input? integer, double, float, String?

Answer 12

Math function always uses a double so do not assign anything else with it otherwise you will have errors.