Java SE 11: Encapsulation

Question 1

static is a ______ that we apply to a method or a variable

Answer 1

modifier

Question 2

_____ means that the method or variable belongs to the class and is shared by all objects in that class

Answer 2

static

Question 3

a static modifier means it’s not unique to an object instance, and it can be accessed without _________ the class. So we don’t need to use the ___ keyword, and no constructor gets called when we access static methods or variables

Answer 3

a static modifier means it’s not unique to an object instance, and it can be accessed without instantiating the class. So we don’t need to use the NEW keyword.

Question 4

A constructor gets called when we access static methods or variables.

True or False

Answer 4

False

You don’t need to use the new keyword, and no constructor gets called when we access static methods or variables

Question 5

An _______ vairable is unique to an individial object

Answer 5

Instance

Question 6

In the following ItemSizes class does a ItemSizes object need to be instatied in order to access it’s members?

Yes or No

public class ItemSizes {

public static String mSmall = “Mens Small”

}

}

Answer 6

No

since the member is static it can be accessed without having to create the ItemSizes class

Question 7

an ______ _____ is a non-static method

Answer 7

instance method

Question 8

Is the setSize() method an instance method or static method?

public class Item {

public String size;

public void setSize(String sizeArg) {

size = sizeArg;

}

}

Answer 8

Instance method

Question 9

How do you make a variable a constant?

Answer 9

using the final keyword before the variable type name

ex. final int COLUMNS

Question 10

constant variables can be changed after they have been initialized.

True or False

Answer 10

False

Constants cannot be changed after they have been initialzed.

Question 11

The name of variables declared class ______ should always be uppercase

Answer 11

constants

Question 12

What is called when the compiler changes the type of variable to a type that supports a larger size?

Answer 12

Promotion

Question 13

Some promotions are done automatically by the compiler

True or False

Answer 13

True

Question 14

Feature of promotion is to avoid ________ values.

Answer 14

Truncated

Question 15

We use ____ _______ to lower the range of a value

Answer 15

type casting

Question 16

Type casting a value has no effect on the amount of memory the value consumes.

True or False

Answer 16

False

Type casting reduces the amount of memory used by the value. Ex. change and long value to an int

Question 17

is the example below a promotion or type casting?

int i = 3;

long l = i;

double d = 3;

Answer 17

Promotion

Question 18

In the example below will the num3 value be truncated?

Yes or No

int num1 = 55555;

int num2 = 66666;

long num3 = num1 * num2;

Answer 18

Yes

Question 19

In the example below the result num3 is 3.7 billion which is too large to fit in an int type. What do i need to change to ensure the final number is truncated.

int num1 = 55555;

int num2 = 66666;

long num3 = num1 * num2;

Answer 19

Either num1 or num2 needs to be changed to a long type.

Question 20

How would you convert the number represented as a string to a primitive type?

String sNum = “150”;

int intNum = ________________ ;

Answer 20

int nNum = Integer.parseInt(sNum);

Question 21

How would you convert the boolean represented as a string to a boolean type?

String nNum = “true”;

boolean b = ______________;

Answer 21

boolean b = Boolean.parseBoolean(sNum);

Question 22

How would you modify the code below to make the setID method private but still accessible?

public class item {

print int id;

print String desc;

public item () {

desc= “–description required–”;

}

public void setId() {

id = Item.nextId++;

}

Answer 22

public class item {

print int id;

print String desc;

public item () {

setID();

desc= “–description required–”;

}

private void setId() {

id = Item.nextId++;

}

Question 23

In encapsulation, the variables of a class will be _____ from other classes, and can be accessed only through the methods of their current class.

Answer 23

Hidden

Question 24

Encapsulation uses access control to hide the fields, so we can provide safe access through ______ and ______ methods.

Answer 24

….. getter and setter methods.

Question 25

Encapsulation encourages good _____ ______design

Answer 25

object-oriented

Question 26

If you make attributes private, how can another object access them?

Answer 26

One object can access the private attributes of a second object. If the second object provides public methods for each of the operations that are to be performed on the value of an attribute.

IE. Getter and setter methods

Question 27

The below is an example of a Setting Method with ________

public void setColorCode(char newCode) {

if (newCode == ‘R’) {

colorCode = newCode;

return;

}

if (newCode == ‘G’) {

colorCode = newCode;

return;

}

if (newCode == ‘B’) {

colorCode = newCode;

return;

}

System.out.println(“Invalid colorCode. Use R, G, or B”);

}

Answer 27

Checking