Variables (Head First Java Ch.3)

Question 1

Why isn’t it possible to store an int into a byte:
int x = 24;
byte b = x;

Answer 1

a byte is 8 bits, while an int is 32 bits. So it is not possible to store something large into something smaller

Question 2

What are the rules for naming variables?

Answer 2

1. It cannot START with a number. It can contain numbers afterwards
2. It cannot be one of Java’s reserved names (keywords, primitive types)

Question 3

What is stored in Stack?

Answer 3

local primitive data variables, and references to objects

Question 4

What is stored in Heap?

Answer 4

objects themselves

Question 5

How do we access a method through an object?

Answer 5

Using the dot operator(.) followed by the method name we wish to access . We can include arguments to pass to the method if applicable.

Question 6

Book b = new Book() ;
Book c = new Book() ;

b = c;

Are these variables pointing to different objects?

Answer 6

Because of the last line of code, b and c are pointing the same “Book object”

Question 7

How can we declare an array of objects?

Answer 7

1. Declare array variable and set length:

Dog[] pets = new Dog[7];

2. create new Dog objects and set them to array elements

pets[0] = new Dog();
pets[1] = new Dog();