Character and string Methods Flashcards by Nasrifa A. Manda

A ___________ is not a simple data type but a reference—it holds a memory address, not the actual
value.

String variable

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A String variable is _____________ but a reference—it holds a memory address, not the actual
value.

not a simple data type

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A String variable is not a simple data type but a _________—it holds a memory address, not the actual
value.

reference

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A String variable is not a simple data type but a reference—it holds a _____________, not the___________.

memory address
actual value

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When you use __ to compare two
Strings, you’re comparing their _____________, not their ________.

==
memory addresses
actual values

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_________ usually want to compare the values
of Strings, not their memory addresses.

Programmers

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Programmers usually want to compare the ___________, not their___________.

values of Strings
memory addresses

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______________:
Holds a single character

Character Class

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Character Class:
Holds a _________

single character

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______________:
Provides methods to manipulate and inspect
single-character data.

Character Class

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Character Class:
Holds a single character (e.g., ‘A’, ‘8’, ‘$’).
Provides methods to ________ and ______________.

manipulate
inspect single-character data

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___________:
Used for fixed (unchanging) text data made
up of one or more characters.
Offers many methods to simplify working with
Strings.

String Class

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String Class:
Used for_______________ made
up of _______________.
Offers many methods to simplify working with
Strings.

fixed (unchanging) text data
one or more characters

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The _____________:
Used to store a single character, such as a
letter, digit, or punctuation mark.

char Data Type

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The char Data Type:
Used to _____________, such as a
letter, digit, or punctuation mark.

store a single character

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The char Data Type:
Used to store a single character, such as a
_______,________, or_____________.

letter
digit
punctuation mark

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char literals are written inside_______________

single quotation
marks

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Since char is a _____________, it holds
actual values (not memory addresses).

primitive data type

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Since char is a primitive data type, it holds
___________ (_________).

actual values
not memory addresses

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You can compare char values using _______________ like == and >.

relational operators

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Comparisons are based on the ________ value of
each character.

Unicode

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These comparisons work as you’d expect—
_____________.

alphabetically

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Java also provides a _________ for working
with characters.

Character class

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This class includes useful methods for_______ and
__________ character values.

testing
manipulating

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This __________ includes useful methods for testing and manipulating character values.

class

The ____________ is part of the____________, which is automatically imported into every Java program.

Character class java.lang package

Checks if the given character is a letter (uppercase or lowercase).

isLetter(char ch)

Checks if the given character is a digit

isDigit(char ch)

Checks if the given character is a whitespace (space, tab, newline, etc.).

isWhitespace(char ch)

Converts the given character to its uppercase equivalent.

toUpperCase(char ch)

Converts the given character to its lowercase equivalent.

toLowerCase(char ch)

Checks if the given character is an uppercase letter.

isUpperCase(char ch)

Checks if the given character is a lowercase letter.

isLowerCase(char ch)

Converts the given character to a String.

toString(char ch)

Checks if the given character is a letter or a digit.

isLetterOrDigit(char ch)

Compares two characters numerically based on their Unicode values.

compare(char x, char y)

Compares two characters numerically based on their _______________.

Unicode values

_____________ are one of the most common dataType in Java.

Strings

Strings are one of the most common ______ in Java.

dataType

Primitive Types (e.g., int): When you declare int x = 10;, the __________ of x holds the value 10. If you update x to 45, the _____ replaces the old one at the same memory address.

memory address new value

When you declare String aGreeting = "Hello";, aGreeting holds the ____________ of the String "Hello", not the ________.

memory address actual characters

You cannot choose _________; they are assigned by the __________.

memory addresses operating system

Strings are ____________they are never changed. Instead, new Strings are created, and references are updated to point to the new memory addresses.

immutable

Strings are immutable—they are never changed. Instead, ________ are created, and _________ are updated to point to the ______________.

new Strings references new memory addresses

Comparing Strings with < or > will cause a ________________. These operators cannot be used with Strings.

compilation error

Use the + operator to combine (concatenate) Strings.

Concatenating Strings

Created using double quotes with no characters inside.

Empty Strings

Refers to a memory address where no characters are stored.

Empty String

Refers to a_________ where _________ are stored. Can be used with String methods like ________.

memory address no characters .equals()

_________: Created by assigning null to a String.

Null Strings

A _________ does not reference any memory address.

null String

Cannot be used with String methods like___________ —it will cause an error.

.equals()

Others find it ________ since unassigned Strings are null by default.

redundant

Returns the number of characters in a String.

length()

Finds the position of a character or substring in a String.

indexOf()

Returns the character at a specific position.

charAt()

Extracts part of a String.

substring()

The __________ method takes_______________—a start position and an end position—that are both based on the fact that a String’s first position is position zero.

substring() two integer arguments

The_________________ is the difference between the second integer and the first integer; if you call the method without a second integer argument, the substring extends to the end of the original string.

length of the extracted substring

The length of the extracted substring is the difference between the _________________; if you call the method without a second integer argument, the substring extends to the end of the original string.

second integer and the first integer

Checks if a String starts with a specific substring.

startsWith()

Checks if a String ends with a specific substring

endsWith()

Replaces all occurrences of a character or String/substring.

replace()

Checks if a String contains a specific substring.

contains()

Converts current dataType to a String (implicitly used in print() and println()).

toString()

Finds the position of a substring starting from a specific index.

indexOf(String, int)

Checks if a String is empty or contains only whitespace.

isBlank()

Checks if a String has no characters.

isEmpty()

Converts the String to lowercase.

toLowerCase()

Converts the String to uppercase.

toUpperCase()

Removes leading and trailing whitespace.

strip()

Removes leading and trailing whitespace (similar to strip() but available in older Java versions).

trim()

Why Convert Strings to Numbers?

perform arithmetic operations.

It provides the _______________ method, which takes a String and returns its integer value.

parseInt()

parseInt() is a static method, so you call it using the class name (___________).

Integer.parseInt()

It provides the ___________method, which takes a String and returns its double values.

parseDouble()

indexOf(): Finds the position of a character or substring in a String. Returns ______ if not found.

-1

Converts a String to a float.

Float.parseFloat():

Converts a String to a long.

Long.parseLong()

Forgetting to handle null Strings, leading to ____________.

runtime errors

Misusing methods like charAt() with invalid positions (causing ______________________).

StringIndexOutOfBoundsException

Character and string Methods Flashcards

(81 cards)