chapter 7 (so far)

Question 1

What is a string

Answer 1

-A String is a class
-Each created String is a class object
The String variable name is not a simple data type
-Holds the memory address of a string and is immutable

Question 2

Reference

Answer 2

A variable that holds a memory address

Question 3

What does the == operator do regarding strings

Answer 3

it compares the memory locations of the strings rather than their values
-Compares constants of the memory locations more frequently than memory locations themselves

Question 4

What class to use for character

Answer 4

• Char/ Character
• holds a single character value
• defines methods that can manipulate or inspect single-character data

Question 5

What class to use for working with fixed string data and unchanging data composed of multiple characters

Answer 5

string

Question 6

What are StringBuilder and StringBuffer

Answer 6

Classes for storing and manipulating changeable data composed of multiple character

Question 7

Describe the character class’ methods

Answer 7

Methods that begin with “is” such as isUpperCase() return a boolean value that can be used in comparison statements
Methods that begin with “to” such as toUpperCase() return a character that have been converted to the stated format

Question 8

literal string

Answer 8

A sequence of characters enclosed within double quotation marks
An unnamed object, or anonymous object, of the String class

Question 9

String variable

Answer 9

A named object of the String class

Question 10

Class String

Answer 10

Defined in java.lang.String

Automatically imported into every program

Question 11

What is the relation between the string and variable assigned to it

Answer 11

the string itself is distinct from the variable used to refer to it

Question 12

string variable name

Answer 12

a reference to a variable

refers to a location in memory rather than a particular variable

Question 13

What happens when a new value is given to a string

Answer 13

the address held by the string is altered

Question 14

immutable

Answer 14

unchanging objects such as strings
this means making simple comparisons between strings produces sometimes misleading results
-Compares memory addresses, not values

Question 15

equals() method

Answer 15

Evaluates the contents of two String objects to determine if they are equivalent
Returns true if objects have identical contents
public boolean equals(String s)

Question 16

equalsIgnoreCase() method

Answer 16

Ignores case when determining if two Strings are equivalent

Useful when users type responses to prompts in programs

Question 17

compareTo() method

Answer 17

Compares two Strings and returns:
-Zero: If two Strings refer to the same value
-Negative number: If the calling object is “less than” the argument
-Positive number: If the calling object is “more than” the argument
if (aWord.compareTo(anotherWord) < 0)

Question 18

What is an empty string

Answer 18

Reference a memory address with no characters

Can be used in String methods

Question 19

null string

Answer 19

• Use the null Java keyword
• Strings are set to null by default
• Cannot be used in String methods

Question 20

toUpperCase() and toLowerCase()

Answer 20

Convert any String to its uppercase or lowercase equivalent

Question 21

length()

Answer 21

Returns the length of a String

Question 22

indexOf() method

Answer 22

Determines whether a specific character occurs within a String
Returns the position of the character
The first position of a String is zero
The return value is –1 if the character does not exist in the String

Question 23

charAt() method

Answer 23

Requires an integer argument

Indicates the position of the character that the method returns

Question 24

endsWith() method and startsWith()

Answer 24

• Each takes a String argument

- Return true or false if a String object does or does not end or start with the specified argument, respectively

Question 25

replace()

Answer 25

Replaces all occurrences of some character within a String

Question 26

toString()

Answer 26

``` Not part of the String class Converts any object to a String Converts primitive data types to Strings String theString; int someInt = 4; theString = Integer.toString(someInt); ```

Question 27

Concatenation

Answer 27

Join a simple variable to a String String aString = "My age is " + myAge; Use the + operator

Question 28

substring()

Answer 28

``` Extracts part of a String Takes two integer arguments -Start position -End position The length of the extracted substring is the difference between the second integer and the first integer ```

Question 29

regionMatches()

Answer 29

Two variants that can be used to test if two String regions are equal

Question 30

when is A substring of the specified String object is compared to a substring of the other

Answer 30

If the substrings contain the same character sequence, then the expression is true Otherwise, the expression is false A second version uses an additional boolean argument Determines whether case is ignored when comparing characters

Question 31

Integer class

Answer 31

``` Part of java.lang Automatically imported into programs Converts a String to an integer parseInt() method Takes a String argument Returns its integer value ```

Question 32

Wrapper

Answer 32

A class or an object “wrapped around” a simpler element

Question 33

Integer class valueOf() method

Answer 33

Part of java.lang Automatically imported into programs Converts a String to an integer

Question 34

parseInt() method

Answer 34

Takes a String argument | Returns its integer value

Question 35

Wrapper

Answer 35

A class or an object “wrapped around” a simpler element

Question 36

Integer class intValue() method

Answer 36

Extracts the simple integer from its wrapper class

Question 37

Double class

Answer 37

``` A wrapper class Imported into programs automatically parseDouble() method Takes a String argument and returns its double value ```

Question 38

StringBuilder and StringBuffer classes

Answer 38

``` An alternative to the String class Used when a String will be modified Can use anywhere you would use a String Part of the java.lang package Automatically imported into every program ```

Question 39

Compare StringBuilder and StringBuffer

Answer 39

StringBuilder is more efficient | StringBuffer is thread safe and used in multithreaded programs

Question 40

Buffer

Answer 40

A memory block Might or might not contain a String The String might not occupy the entire buffer The length of a String can be different from -the length of the buffer Capacity -The actual length of the buffer

Question 41

setLength() method

Answer 41

Changes the length of a String in a StringBuilder object

Question 42

length property

Answer 42

``` An attribute of the StringBuilder class Identifies the number of characters in the String contained in the StringBuilder ```

Question 43

capacity() method

Answer 43

Finds the capacity of a StringBuilder object

Question 44

What do StringBuilder objects do

Answer 44

Provides improved computer performance over String objects | Can insert or append new contents into StringBuilder

Question 45

append() method

Answer 45

Adds characters to the end of a StringBuilder object

Question 46

insert() method

Answer 46

Adds characters at a specific location within a StringBuilder object

Question 47

setCharAt() method

Answer 47

Changes a character at a specified position within a StringBuilder object

Question 48

charAt() method

Answer 48

Accepts an argument that is the offset of the character position from the beginning of a String Returns the character at that position