Chapter 1: Java Building Blocks

Question 1

T or F: A file can contain multiple classes.

Answer 1

True. But at most one public class.

Question 2

T or F: A public class within the file ClassA.java can be named ClassB

Answer 2

False. A public class must be in a file of the same name

Question 3

What is the file extension is used for bytecode files?

Answer 3

.class

Question 4

T or F: Every java file requires a package declaration

Answer 4

False. Package declaration is optional

Question 5

T or F: Constructors can have a return type

Answer 5

False

Question 6

T or F: It is optional to include a constructor in a class

Answer 6

True. There is a default do-nothing constructor

Question 7

Where do you put code initializer blocks?

Answer 7

Within a class, outside of methods.

Question 8

Which runs first, code initializer block or field initialization?

Answer 8

Depends on the order they appear in the class

Question 9

When does a constructor’s code block run?

Answer 9

After field and initializer blocks are done

Question 10

T or F: You can refer to a field before it is initialized

Answer 10

False

Question 11

What type of data does the following primitive hold?

Boolean

Answer 11

True or false

Question 12

What type of data does the following primitive hold?

byte

Answer 12

8-bit integral value

Question 13

What type of data does the following primitive hold?

short

Answer 13

16-bit integral value

Question 14

What type of data does the following primitive hold?

int

Answer 14

32-bit integral value

Question 15

What type of data does the following primitive hold?

long

Answer 15

64-bit integral value

Question 16

What type of data does the following primitive hold?

float

Answer 16

32-bit floating-point value

Question 17

What type of data does the following primitive hold?

double

Answer 17

64-bit floating-point value

Question 18

What type of data does the following primitive hold?

char

Answer 18

16-bit Unicode value

Question 19

T or F: A float literal doesn’t need the ‘f’ after it

Answer 19

False. Floating point literals are assumed to be doubles unless the ‘f’ is present

Question 20

What is the max value of a byte?

Answer 20

127

Question 21

What is the min value of a byte?

Answer 21

-128

Question 22

What does it mean to have a numeric literal followed by an ‘L’?

Answer 22

It’s data type is long

Question 23

How do you write an octal literal?

Answer 23

Prefix with ‘0’

Question 24

How do you write a hex literal?

Answer 24

Prefix with ‘0x’

Question 25

How do you write a binary literal?

Answer 25

Prefix with ‘0b’

Question 26

A numeric literal can contain ‘_’. Where can’t the underscore go?

Answer 26

• At the beginning or end of the literal.

- Immediately before or after a decimal.

Question 27

Can a primitive be null?

Answer 27

No, but a reference variable can be null

Question 28

Can a primitive be used to call methods?

Answer 28

No, but reference variables can

Question 29

Is
String s1, s2 = “s2;
valid?

Answer 29

Yes. Multiple variables of the same type can be declared on the same line. Not all need to be initialized

Question 30

Is
String s1, long l1, l2 = 12L;
valid?

Answer 30

No. You can only declare variables in the same line if they are the same type.

Question 31

What characters can identifiers start with?

Answer 31

Identifiers must start with a letter, $, or _. Subsequent characters can be numbers

Question 32

Is ‘public’ a valid identifier?

Answer 32

No. ‘public’ is a reserved word in Java

Question 33

Is ‘Public’ a valid identifier?

Answer 33

Yes. Although ‘public’ is a reserved word, Java is case sensitive, so ‘Public’ is valid

Question 34

What are the two unused reserved words?

Answer 34

const and goto

Question 35

Do local variables have default initialization?

Answer 35

No

Question 36

What is the default value of a boolean instance variable?

Answer 36

false

Question 37

What is the default value of a integral instance variable?

Answer 37

0

Question 38

What is the default value of a floating point instance variable?

Answer 38

0.0

Question 39

What is the default value of a char instance variable?

Answer 39

‘\u0000’ (NUL)

Question 40

What is the default value of a reference instance variable?

Answer 40

null

Question 41

What is the scope of a local variable?

Answer 41

The method/block in which it is defined

Question 42

What is the correct order of the following elements in a file?

Import statements
package declaration
class declaration

Answer 42

Package declaration
Import statements
class declaration

• Package declaration and import statements are optional

Question 43

Is System.gc() guaranteed to run?

Answer 43

No

Question 44

What makes an object eligible for garbage collection?

Answer 44

It has no references pointing to it.

All references to it are out of scope

Question 45

Is finalize() guaranteed to run?

Answer 45

No

Question 46

T or F: If an object’s finalize method is called and it’s not successfully destroyed, the finalize method could run again later.

Answer 46

False. The finalize method can run at most one time.

Question 47

What are the 6 main benefits of java?

Answer 47

Object oriented
encapsulation
platform independent
robust
simple
secure