Ch 1 - Java Building Blocks

Question 1

Java classes have two primary building blocks, what are they?

Answer 1

methods and fields

Question 2

Methods and fields are the ? of the class

Answer 2

members

Question 3

The full declaration of a method is called a what?

Answer 3

method signature

Question 4

What are the three types of comments?

Answer 4

1. single line:
// comment
2. multi line:
/*
*  comment
*/
3. java doc:
/**
*	java doc comment
*/

Question 5

You can put multiple classes in the same file, but at most ? can be public

Answer 5

one

Question 6

The public class must match what?

Answer 6

…match the file name

Question 7

true/false: a file can contain multiple classes where none of them is public

Answer 7

true

Question 8

What is the lack of any access modifier for a class?

Answer 8

The default package private modifier

Question 9

What does the default package private modifier indicate?

Answer 9

indicates the class can be accessed only by a class within the same package.

Question 10

Give the class signature for the default package private modifer

Answer 10

class Defaultclass {}

Question 11

How many access modifiers are there for classes?

Answer 11

two: public and default

Question 12

To compile java code, the file must have an extension of what?

Answer 12

.java

Question 13

The result of compiling is a bytecode file with a ? extension.

Answer 13

.class

Question 14

What is the name of the one special package in java?

Answer 14

java.lang

Question 15

Why is java.lang special?

Answer 15

it is special because it is automatically imported.

Question 16

How many wildcards can you have in an import statement?

Answer 16

one

Question 17

true/false: In an import, a wildcard matches class names

Answer 17

true

Question 18

true/false: In an import, a wildcard matches sub package class names?

Answer 18

false

Question 19

true/false: In an import, you can import methods

Answer 19

false

Question 20

An object is a ? of a class.

Answer 20

an instance

Question 21

the name of the ? matches the name of the class and there’s no return type.

Answer 21

constructor

Question 22

Is this a constructor:

public void Chick() { }

Answer 22

no, because it has a return type

Question 23

What happens if you do not provide a constructor?

Answer 23

The compiler will supply a do nothing default constructor for you.

Question 24

What is an instance initializer block?

Answer 24

a code block outside of a method.

Question 25

A code block is any code surrounded with what?

Answer 25

{ }

Question 26

What is the order of initialization?

Answer 26

- static variables and static initializers in order - instance variables and instance initializers in order - constructors

Question 27

Name the eight primitive types

Answer 27

``` byte short int long float double char boolean ```

Question 28

When a number is present in the code, what is it called?

Answer 28

it is called a literal.

Question 29

Why won't this compile: | long max = 3123456789;

Answer 29

Need to include the "L" char at the end of the number.

Question 30

When including the "L" char to indicate a long, does it have to be upper or lower case?

Answer 30

It can be either.

Question 31

What does an octal number use as a prefix?

Answer 31

0. For example: 017

Question 32

What does a hexidecimal number use as a prefix?

Answer 32

the number 0 followed by x or X as a prefix, for example 0xFF

Question 33

What does a binary number use as a prefix?

Answer 33

the number 0 followed by b or B as a prefix, for example 0b10

Question 34

Does this compile: | double d = _1000.00

Answer 34

no

Question 35

Does this compile: | double d = 1000.00_;

Answer 35

no

Question 36

Does this compile: | double d = 1000_.00;

Answer 36

no

Question 37

Does this compile: | double d = 1_00_0.0_0;

Answer 37

yes

Question 38

Can you assign null to a primitive type?

Answer 38

no

Question 39

Can you assign null to a reference type?

Answer 39

yes

Question 40

A reference can be assigned to a new object using the ? keyword.

Answer 40

new

Question 41

Reference types can be used to call methods when they do not point to ?

Answer 41

null

Question 42

Do primitives have methods declared on them?

Answer 42

no

Question 43

All primitive types have what case names?

Answer 43

lowercase

Question 44

All reference type classes that come with Java begin with an ? case letter.

Answer 44

upper

Question 45

Is this declaring or initializing a variable: | String zooName;

Answer 45

declaring

Question 46

Is this declaring or initializing a variable: | int numberAnimals;

Answer 46

declaring

Question 47

Is this declaring or initializing a variable: | zooName = "The Best Zoo";

Answer 47

initializing

Question 48

Is this declaring or initializing a variable: | numberAnimals = 100;

Answer 48

initializing

Question 49

true/false: this code compiles: | String s1, s2;

Answer 49

true

Question 50

true/false: this code compiles: | String s3 = "yes", s4 = "no";

Answer 50

true

Question 51

true/false: this code compiles: | int num, String value;

Answer 51

false

Question 52

true/false, this code compiles: | double d1, double d2;

Answer 52

false

Question 53

You can declare many variables in the same declaration as long as they are all ...

Answer 53

of the same type

Question 54

true/false, this code compiles: | int i1; i2;

Answer 54

false

Question 55

Name the rules for identifiers

Answer 55

- must begin with a letter or the symbol $ or _ - subsequent characters may also be numbers - You cannot use the same name as a Java reserved word. Java is case sensitive, so you can use versions of the keywords that only differ in case.

Question 56

``` true/false, this code compiles: public int mymethod() { int y = 10; int x; int reply = x + y; return reply } ```

Answer 56

false. int x isn't initialized.

Question 57

true/false, this code compiles: public void findAnswer(boolean check) { ``` int answer; int onlyOneBranch; if(check) { onlyOneBranch = 1; answer = 1; } else { answer = 2; } System.out.println(answer); System.out.println(onlyOneBranch); } ```

Answer 57

false. int onlyOneBranch has not been initialized.

Question 58

Variables that are not local variables are known as ...

Answer 58

instance or class variables

Question 59

You can tell a variable is a class variable because it has what keyword before it?

Answer 59

static

Question 60

Which variable(s) have default values: instance local class

Answer 60

instance and class

Question 61

``` Give the default initialization values for the given variable types: boolean byte, short, int, long float, double all object references ```

Answer 61

``` false 0 (in the type's bit length) 0.0 (in the type's bit length) null ```

Question 62

When are instance variables in scope?

Answer 62

instance variables are in scope as soon as they are defined and last for the entire lifetime of the object itself.

Question 63

When are static variables in scope?

Answer 63

static variables go into scope when declared, and they stay in scope for the entire lifetime of the program.

Question 64

When are local variables in scope?

Answer 64

in scope from declaration to end of block

Question 65

Name the ordering of elements in a class

Answer 65

``` package declaration - first line in a file imports - immediately after package definition class definition - immediately after the imports field declarations - anywhere inside a class method declarations - anywhere inside a class ```

Question 66

What is the heap?

Answer 66

The heap, which is also known as the free store, represents a large pool of unused memory allocated to your Java application.

Question 67

Is a reference on the heap?

Answer 67

A reference may or may not be created on the heap. All references are the same size, no matter what their data type is and are accessed by their variable name.

Question 68

Are objects on the heap?

Answer 68

Objects are always on the heap.

Question 69

What is garbage collection?

Answer 69

Garbage collection refers to the process of automatically freeing memory on the heap by deleting objects that are no longer reachable in your program.

Question 70

What is the purpose of System.gc()?

Answer 70

It suggests that now might be a good time for Java to kick off a garbage collection run.

Question 71

true/false: System.gc() guarantees that garbage collection will be run

Answer 71

false

Question 72

true/false: finalize() will get called and could get called more than once

Answer 72

false, it might not get called and it definitely will not get called twice

Question 73

Name some of the benefits of java

Answer 73

- Object Oriented - Encapsulation - Platform Independent - if you get asked on the exam, all classes run everywhere. - Robust - Simple - Secure