ap comp sci unit 2 test

Question 1

state/attributes

Answer 1

instance variables in java

Question 2

behavior

Answer 2

methods in Java

Question 3

Class

Answer 3

Blueprint for objects

Question 4

Overloading

Answer 4

Having many constructors with same name but different constructor signatures (parameters)

Question 5

non static methids

Answer 5

objectName.method();

Question 6

NullPointerException

Answer 6

Creating a non static method on a null object = error

Question 7

name.concat(“value”)

Answer 7

Returns a new String with “value” appended to the end of name

Question 8

name.replace(“a”, “p”)

Answer 8

Returns a new STring will all instances of “a” replaced with “p”

Question 9

Strings are immutable

Answer 9

They cannot be changed but we can reassign it

Question 10

"

Answer 10

Allows for quotation marks
““\monkey/””

Question 11

\

Answer 11

Includes a backlash
At the end
Ex: Includes a backlash\

Question 12

\n

Answer 12

“This creates \na line break
This creates
a line break

Question 13

\t

Answer 13

“This adds a \ttab space”
“This adds a tab st[ace

Question 14

name.length

Answer 14

Returns the number of characters in a String object ( returns an int)

Question 15

name.substring(4)

Answer 15

Returns the substring beginning at index 4 and ending at the last index

Question 16

name.subString(2,6)

Answer 16

Returns the substring at index 2 and ends at 5

Question 17

name.equals(“Hello”)

Answer 17

Returns trye if name is equal to Hello
Returns false otherwise

Question 18

name.CompareTo(“Hello”)

Answer 18

Returns a value < 0 if name is less than Hello
Returns 0 if name is equal to Hello
Returns a value > - if name is greater than Hello

Question 19

numerical value

Answer 19

Starts from A is 65, Z is 90, ends at 126. 6 spaces between “Z’ and “a’

Question 20

name.IndexOf(“d”)

Answer 20

Returns the index of the first occurence of d (returns an int)
Returns -1 if not found

Question 21

Primitive

Answer 21

Most basic type in java, primitive variables store primitive values, don’t have associated methods

Question 22

Reference

Answer 22

Instantiable classes made by programmers that often use primitive types, reference variables store the address of the value, has associated methods

Question 23

Ex of primtive types

Answer 23

boolean, char, int double (anythign lowercase)

Question 24

ex of reference types

Answer 24

Interger, Double (anythign with uppercase)

Question 25

Integer.intValue();

Answer 25

converts Integer into int value

Question 26

wrapping purpose

Answer 26

Double > double > int > Integer
(Java already knows how to change int into Integer)

Question 27

Autoboxing

Answer 27

Java knows how to
int > Integer
double > Double

Question 28

Unboxing

Answer 28

Integer > int
Double > double

Question 29

Unboxing and Autoboxing purpose

Answer 29

Allows objects to be ised interchangeably without having to perform any casting explicitly.

Question 30

Non static method

Answer 30

Needs to be called with an object
objectName.methodName();

Question 31

Instance method

Answer 31

public int getWidth()

Question 32

Static method

Answer 32

Doesn’t need any objects
Classname.methodName();

Question 33

General formula for generating any number from start to num

Answer 33

int rand = (int)(Math.random() * (range + 1)):

Question 34

If we are not starting from 0, we add numbers to the random

Answer 34

int rand = (int)(Math.random() * (range + 1) + start)