AP

Question 1

WHEN GIVEN A METHOD USE THE METHOD MAKE UR CODE EFFICIENT PLEASE GOOD GOLLY GOD GOSH JEEZ LoUIS

Question 2

can you use == for doubles?

Answer 2

NAHHHH, only for ints and booleans (because giant doubles are approximations of real numbers)

Question 3

point of wrappers

Answer 3

such as arrraylists, to put ints and doubles into an object-only area

Question 4

if you fail to initalize a local variable in a method, this is the only case where…

Answer 4

the variable does NOT get initalized to null/default automatically

Question 5

4/23/24 camera roll

Question 6

“removed.add(memberList.get(i))

memberList.remove(i)
“
can be simplified down to:

Answer 6

remove.add(memberList.remove(i));

Question 7

super.method or method.super?

Answer 7

super.method(PARAMETER(s))

Question 8

can you overload an inherited method?

Answer 8

yes!

Question 9

you can declare variables in a loop and have it just keep getting redeclared and adjust for every object buster

Question 10

what do you use for a boolean, .equals or ==?

Answer 10

==

Question 11

why cant you edit a for each loop?

Answer 11

because such as in for ( int num : nums), num is a variable declared in the header, or a COPY of nums. editing num edits the instance variable

Question 12

modifier methods are what make an object…

Answer 12

mutable (integer class is immutable)

Question 13

lists can be mutable if youre in a class and you have a _____ via a for each loop

Answer 13

modifer method

Question 14

true/false: subclasses inherit the constructors of superclasses

Answer 14

false, they need to specify their own constructors (unless the subclass has no constructors, in which java creates an automatic no args)

Question 15

12-2-10: When will the method stringRecursion produce a run time error?

public void stringRecursion(String s)
{

if (s.length() < 16)
{
System.out.println(s);
}
stringRecursion(s + “*”);
}
A. It will never produce a run time error.
B. It will always produce a run time error.
C. Only when the length of the input string is greater than or equal to 16.
D. Only when an empty string is input.
E. Whenever the input string length is less than 16.

Answer 15

B, the length conditional is within the if but the increases in length via extra *’s are outside the if

Question 16

12-2-17: Consider the following method. Assume that String s = “rain”; and int b = 4; have been executed. What are the values of s and b after test(s,b) is executed?

public static void test(String str, int y)
{
str = str + “bow”;
y = y * 2;
}
A. s=”rainbow”; b=8;
B. s=”rain”; b=8;
C. s=”rainbow”; b=4;
D. s=”rain”; b=4;
E. s=”bow”; b=4;

Answer 16

D, strings are immutable so changes mean you create a new string, s is unaffected. primitive types are COPIED, and nothing is done to b as they are PASSED BY VALUE (only the value is passed to the method, not the reference variable)

Question 17

when is pass by value used?

Answer 17

in method calls, wherein the VALUE of the PRIMITIVE parameters, not the actual reference/memory location itself are used. methods use a copy basically

Question 18

when is pass by reference used?

Answer 18

while java technically never uses pass by reference, the pass by value of objects is effectively the same thing

an object reference is passed as a method parameter and can be altered OUTSIDE the confines of that method by something within the method

Question 19

12-2-18: Which of the following is/are true about using insertion sort versus using merge sort?

I. Insertion sort requires more storage space than mergesort.
II. Insertion sort is only more efficient than mergesort in the case that we have a very small and nearly sorted array.
III. Insertion sort is almost always less efficient than mergesort.
A. I only
B. II only
C. III only
D. I and III
E. II and III

Answer 19

E✔️ Merge sort uses the “divide and conquer” approach to sort an array. This will end up being more efficient than insertion sort in the case where we have long unordered array. However if we have a very small almost sorted array, then insertion sort will outperform merge sort.

Question 20

rank the sort types in order of efficiency

Answer 20

merge > insertion > selection

Question 22

how do == and .equals() differ?

Answer 22

FOR STRINGS:
== determines whether or not the names refer to the same OBJECT, whereas .equals() determines whether the VALUE is the same (same vs. equivalent) (cannot use keyword new in the second reference variable)

for everything else:

Question 23

can .super() be used to call a grandparent class’s method?

Answer 23

not unless the parent has a super of that same overridden method

Question 24

given:

int q = 4;
changeN(q);
System.out.println(q);

SEP METHOD:

public static in changeN(int q)

q++;
return q;

what will the code print?

Answer 24

4

Question 25

13-2-11: Assume the following classes.

public class Animal
{
// constructors not shown
public void eat()
{ // code not shown
}
}

public class Bear extends Animal
{
// constructors not shown
public void growl()
{ // code not shown
}
}

Assume that the following declaration is in a different class.
Animal b = new Bear();

Which of the following will compile without error?
I. b.eat();
II. b.growl;
III. ((Bear) b).growl();

Answer 25

1 and 3:

I works since the declared type is Animal and Animal has an eat method. III works because the cast tells the compiler to treat b is a Bear and Bear has a growl method.

II does NOT work because java looks for methods based on the DECLARATION type, and as such will not be able to find specific methods only found in bear.

Question 26

declared type vs actual type

Answer 26

the declared type (the left side of the = statement) is the type at declaration, and the type which java will parse, looking for the methods used in code. if found, the code will compile, but if not, the code will NOT compile (see bear notecard)

the actual type/type at RUN TIME is the type that the object actually, well, is (right side of the = sign). at run time, as the code managed to compile, java will either find the method or keep going up all the way to the object class to find a method (but it WILL find one!)

if there is a method in the declared type that allows the code to compile, but that same method is overridden in the actual type, then it uses the ACTUAL type duringe execution! (thus, RUN TIME type!)

Question 27

9-6-4: Given the following class definitions and a declaration of Book b = new Dictionary() which of the following will cause a compile-time error?

public class Book
{
public String getISBN()
{
// implementation not shown
}

// constructors, fields, and other methods not shown }

public class Dictionary extends Book
{
public String getDefinition()
{
// implementation not shown
}
}
A. b.getISBN();
B. b.getDefintion();
C. ((Dictionary) b).getDefinition();

Answer 27

B - ✔️ At compile time the declared type is Book and the Book class does not have or inherit a getDefintion method.

Question 28

how does static play into polymorphism?

Answer 28

in an instance like
Animal eshanTanseer = new Dog();
you would call
Animal.makeSound();

or if you called

eshanTanseer.makeSound();

it would give the same result as the animal static makesound method, NOT the dog one, as it was declared as an animal. as the static methods are tied to classes,

it doesn’t actually matter what this individual instance is as static methods are tied to the CLASSES, when java sees animal declaration, it goes for an animal static method, regardless of whether this INDIVIDUAL INSTANCE ( N O T CL A S S ) of animal is ALSO a dog during runtime

Question 29

private int j;

public constructor(int j)
j = j

what happens here?

Answer 29

in the scope of the constructor the PARAMETER takes precedence. thus, the copy of the PARAMETER gets set equal to the field, the default value of which

Question 30

insertion sort (shifts/swaps), selection sort (shifts/swaps)

Answer 30

shifts
swaps

Question 31

null values are compared by…

Answer 31

== (treat it like a primitive, it is the value therefore must be the same thing)

Question 32

object1 = object2
int[]1 = int[]2

vs.

int1 = int2

Answer 32

int1 gets a copy of int2

object1 now references the same memory location of object2

object2’s changes will affect object1 and vise versa, whereas the ints will not do so

int[]s are objects so same things ith them

Question 33

what are the only things that cannot be called with this.?

Answer 33

static stuff, because, yk, no actual object that is “this”, only classes

Question 34

true/false: static methods can change instances

Answer 34

no, but instances can change static stuff (and I do mean all static “stuff”)

Question 35

13-4-9: Consider the following method and if int[] a = {8, 3, 1}, what is the value in a[1] after m1(a); is run?

public int m1(int[] a)
{
a[1]–;
return (a[1] * 2);
}
A. 4
B. 16
C. 7
D. 2
E. 3

Answer 35

D, the return doesn’t actually effect it