Ch. 17-18-19

Question 1

compareTo()

• return type
• definition
• explanation of the format
• static or not

Answer 1

• returns an int
• compares the ASCII values of any object, returning a negative int if the object is less that the compared value, a positive if it is more, and zero if they are equal.
• s.compareTo(“this is what I compare to”);
• not static

Question 2

what is the version of compareTo() that is not case sensitive

Answer 2

.compareToIgnoreCase

Question 3

how many versions of indexOf are there? What do they all do if the search comes up empty?

Answer 3

6, and they all would return -1

Question 4

indexOf(String str)

• return type
• definition
• explanation of the format
• static or not

Answer 4

• returns an int
• returns the index of the segment within the String
• s.indexOf(“thing i want index of”);
• not static

Question 5

indexOf(String s, int from)

Answer 5

does the same thing as indexOf(String s) but starts checking from the index of the int parameter (from).

Question 6

indexOf(char ch)

Answer 6

searches from left to right for the first occurrence of the char.

Question 7

indexOf(int ascii)

Answer 7

similar to ch, except instead of giving a char it gives the ascii code of a char

Question 8

indexOf(char ch, int from)

Answer 8

starting from the index ‘from’, checking for char ch.

Question 9

indexOf(int ascii, int from)

Answer 9

similar to indexOf(char ch, int from) except the char is gotten from the character’s ascii code.

Question 10

lastIndexOf()

Answer 10

with six versions, it is exactly the same as indexOf except it starts searching right to left rather than left to right

Question 11

charAt(int indx)

• return type
• definition
• explanation of the format
• static or not

Answer 11

• returns a char
• returns the char that is at the specified index
• s.charAt(3); This returns the character that is at index 3 of the string s.
• not static

Question 12

replace(char old, char new)

Answer 12

replaces all occurrences of the old char with the new char

Question 13

replace(String old, String new)

Answer 13

replaces all occurrences of the old string with the new string

Question 14

s.trim()

not static

Answer 14

removes the whitespace from both ENDS of the String while leaving the interior whitespaces alone.

Question 15

contains(String ss)

• return type
• definition
• explanation of the format
• static or not

Answer 15

• returns a boolean
• returns true if the String contains the String ss
• “something”.contains(“some”); or s.contains(“hay”);
• not static

Question 16

startsWith(String ss)

• return type
• definition
• explanation of the format
• static or not

Answer 16

• return a boolean
• returns true if the string starts with String ss.
• s.startsWith(“something”); or “something”.startsWith(“some”);
• not static

Question 17

delimiters

Answer 17

a series of characters that separates the text presented to a scanner object into separate tokens

Question 18

position of scanner

Answer 18

always BETWEEN two characters (like a cursor) never on top of one

Question 19

what is the default delimeter

Answer 19

whitespace

Question 20

sc.next()

Answer 20

moves position of scanner to right and returns the next complete token.

Question 21

sc.findInLine(“ri”);

Answer 21

returns “ri” and places position right after “ri” in the string.

Question 22

what is the code for whitespace and more than one whitespace

Answer 22

\s and \s+

Question 23

sc.useDelimiter(“xxs”);

Answer 23

delimeter used is now “xxs”

Question 24

what is the code for zero or more whitespace characters

Answer 24

\s*

Question 25

sc.skip(“skipthis”);

Answer 25

advances the position by skipping over “skipthis”. The substring skipped over must occur directly after the current position

Question 26

what is a complete token in Scanner?

Answer 26

a token inbetween two instances of the current delimiter

Question 27

what will be returned if two delimiters are right next to each other?

Answer 27

an empty string, which was “between” the two delimiters.

Question 28

sc.hasNext()

Answer 28

returns true if the String still has a next character for the Scanner position to move over, else it has reached the end of the String

Question 29

was does a * after a delimiter mean?

Answer 29

zero or more occurrences of this delimiter

Question 30

symbol for non-word characters

Answer 30

\W

Question 31

what is the difference between passing arrays to methods and passing say integers.

Answer 31

Integers and other types only transfer copies to the method (the original stays unchanged) while arrays actually physically pass the array, meaning that anything changed changes the original array.

Question 32

s.split(“a”)

not static

Answer 32

CREATES ARRAY by splitting the string into elements between the defined regex, in this case “a”

Question 33

what does | mean when used with split (ex: a|g)

Answer 33

split on a OR g

Question 34

how can split() be used to count the number of occurrences in a string

Answer 34

the length of the split array minus 1 will yield the number of occurrences of whatever regex was defined, though if the regex is at very end, array.length is the number of occurrences.

Question 35

why can’t for-each loops be used to initialize objects in an array?

Answer 35

because the loop uses a local variable to represent each individual element rather than the element itself.

Question 36

what would you use to compare objects that are elements of the array?

Answer 36

.equals

Question 37

what does NullPointerException mean?

Answer 37

the array has not been initialized yet, ergo is pointing to nothing

Question 38

what does null do?

Answer 38

sets all elements of the array to null, so that assigning values after the nullification only yields a NullPointerException

Question 39

System.arraycopy(fromArray, startIndex, endArray, toIndex, howMany)
STATIC: SYSTEM

Answer 39

copies a portion from one array to another array, and is STATIC to the System class.

Question 40

s.toCharArray()

Answer 40

turns a string into an array of chars.

Question 41

String.copyValueOf(ch)

STATIC VARIABLE FOR STRING CLASS

Answer 41

takes the char parameter and copies that into the String. It is a static variable for the String class.

Question 42

what is the logical size

Answer 42

the number of actual element in the array, as opposed to it’s initialized maximum value.

Question 43

what is the physical size?

Answer 43

myArray.length, since it is the initialized length of the array.

Question 44

Arrays.sort(myArray)

Answer 44

sorts the array in ascending order. STATIC meth

Question 45

Arrays.binarySearch(myArray, 2);

Answer 45

STATIC METHOD that returns the index of the last element that contains the value of the key.

Question 46

what has to happen to the array before binarySearch can occur?

Answer 46

it must be sorted in ascending order

Question 47

what does binary search return if it cannot find the key?

Answer 47

it returns the negated index of the element that would have come after the key, if it had been there.

Question 48

Arrays.equals(x, y)

Answer 48

compares two arrays. STATIC

Question 49

Arrays.fill(myArray, value)

Answer 49

static method; fills all spots in the array with the value.

Question 50

Arrays.toString(myArray)

Answer 50

turns it into a String

Question 51

enhanced for loop and read-only

Answer 51

the variable representing values in the for-each loop is local and cannot change the values of the elements.