String/Builder/Array/List methods

Question 1

charAt

Answer 1

(int)
returns char at index int.
String/StringBuilder.

Question 2

String.indexOf

Answer 2

(int(char) | String, ~ | int)

returns first matching index of char or string, -1 otherwise. Second int can be used to set starting point of search.

Question 3

substring

Answer 3

(int, ~ | int )
returns substring from index first int to either the end of the string or point second int, exclusive.
String/StringBuilder.

Question 4

trim

Answer 4

()
returns string with surrounding white space (new lines, spaces, tabs) removed.
String.

Question 5

String.replace

Answer 5

(char, char)|(string, string)

returns string with second char or string wherever first char or string is found.

Question 6

length

Answer 6

()
returns the natural length of the string.
String/StringBuilder.

Question 7

startsWith

Answer 7

(String, ~ | int)
returns boolean telling whether or not the string begins with the first string either at the beginning or at the index second int.
String.

Question 8

endsWith

Answer 8

(String)
returns boolean telling whether or not the string ends with the specified string, starting from the bottom now we’re here.
String.

Question 9

String Operators

Answer 9

+, +=, ==, !=. + may add numbers before strings.

Question 10

StringBuilder Constructors

Answer 10

StringBuilder() - creates empty string builder with capacity of 16.
StringBuilder(int) - creates empty string builder with capacity of int.
StringBuilder(String) - created string builder with capacity of string + 16.

Question 11

append

Answer 11

(*)
returns and mutates StringBuilder with * attached at the end. * can literally be anything. If it is an object whose class has not overridden toString(), classname@hashtag string will be used.
StringBuilder.

Question 12

insert

Answer 12

(int, *) | (int, String | StringBuilder | char[], int, int)
returns and mutates StringBuilder with * (see append) inserted at first int index position. two ints can be added to specify a substring of the string-like second argument from index second int to the third int, exclusive if String or StringBuilder. if char[], the ints stand for starting position and length of substring.
StringBuilder.

Question 13

reverse

Answer 13

()
returns and mutates string builder to its reverse.
StringBuilder.

Question 14

StringBuilder.replace

Answer 14

(int, int, String)
mutates and returns StringBuilder: replaces index positions int to int exclusive with the string. There’s no problem if the second int is over the index; actually, it starts to knock off some of the StringBuilder’s characters without adding white white space.

Question 15

subSequence

Answer 15

(int, int)
returns a string object wrapped around CharSequence reference from first index int to second, exclusive. does not mutate the string builder.
StringBuilder.

Question 16

Array Initializations

Answer 16

Object[] aThing = {reference, reference};

Object[] aThing2= new Object[] {reference};

Object[] aThing3;
aThing3 = new Object[] {reference, reference};

Object[] aThing4= new Object[0];
aThing4[0] = reference;

Question 17

Array.length

Answer 17

array int length accessor.

Question 18

clone

Answer 18

()
returns a shallow cop: array of the same type with references to the same objects inside. ArrayList clone returns Object reference.
Array, ArrayList.

Question 19

ArrayList Creation

Answer 19

import java.util.ArrayList; or util.*;
ArrayList<type> aThing = new ArrayList<type>();
ArrayList<type> aThing2 = new ArrayList<>();
ArrayList<type> aThing3 = new ArrayList();
ArrayList aThing4 = new ArrayList<type>();
ArrayList aThing5 = new ArrayList();
you can place an argument int to specify capacity. default 10.

Question 20

add

Answer 20

(rightReference) | (int index, object)
add an item to the list and return true.
or
adds item to specified location and returns nothing.
ArrayList

Question 21

addAll

Answer 21

(rightArrayList) | (int index, rightArrayList)
These methods add all the references from one array list to the other, at a specified int index.
They return true.
Arraylist is really any collections but for the purposes of test 1, it’s array.
The argument array list type can be something that extends the type of the array list.
ArrayList.

Question 22

remove

Answer 22

(int) | (reference)
removes object at specified int index. returns the removed object. or removes first occurrence of object. returns true if accomplished, false otherwise. uses .equals()
ArrayList.

Question 23

contains

Answer 23

(reference)
returns true if reference is in there or false otherwise. uses .equals().
ArrayList.

Question 24

ArrayList.indexOf

Answer 24

(reference)

returns the index of the first occurrence of the element or -1. uses .equals().

Question 25

lastIndexOf

Answer 25

(reference) returns the index of the final occurrence of the element or -1. uses .equals(). ArrayList.

Question 26

set

Answer 26

(int, rightReference) replaces the object at index int with the reference. returns object which was replaced. ArrayList.

Question 27

clear

Answer 27

() clears all the elements of an array list. returns nothing. ArrayList

Question 28

get

Answer 28

(int) returns the element at the position in the list. ArrayList.

Question 29

size

Answer 29

() returns the number of elements in the list. ArrayList.

Question 30

toArray

Answer 30

() returns an array with references to the objects in the array list. ArrayList.

Question 30

StringBuilder.indexOf

Answer 30

(String, ~ | int) | returns first matching index of string, -1 otherwise. Second int can be used to set starting point of search.

Question 31

concat

Answer 31

(String) + operator in method form String

Question 32

delete

Answer 32

(int, int) mutates and returns StringBuilder, removes characters inbetween indexes, exclusively. StringBuilder

Question 33

deleteCharAt

Answer 33

(int) mutates and returns StringBuilder, removes character at specified index. StringBuilder