Variables in Java ✘【12 minutes】
Summary
TLDRThis video tutorial introduces viewers to the concept of variables in Java programming. It explains that variables act as placeholders for values, similar to algebraic variables, but with the ability to store not only numbers but also text, sentences, and boolean values. The video covers Java's eight primitive data types and the reference data type 'String', detailing the purpose and memory usage of each. It also demonstrates how to declare, assign, and initialize variables, and discusses the differences between primitive and reference data types. The tutorial concludes with practical examples of creating and using variables in Java, including handling large numbers with 'long', fractional numbers with 'float' and 'double', single characters with 'char', and strings.
Takeaways
- 📌 Variables in Java are placeholders for values and behave as the values they contain.
- 📚 Variables can store different data types, including numbers, words, sentences, and boolean values (true or false).
- 🔢 Java has eight primitive data types and a special reference data type called String.
- 🏷 The boolean data type uses one bit of memory and can only hold two values: true or false.
- 🔢 The byte data type can hold integer numbers from -128 to 127, while the short type can hold numbers up to around 32,000.
- 🔑 The int data type uses 4 bytes and can store numbers up to just over 2 billion.
- 🔑 The long data type uses 8 bytes and can store extremely large numbers, from nearly negative nine quintillion to just over nine quintillion.
- 📉 The float data type stores fractional numbers with up to six to seven digits of precision, while the double type has more precision with up to 15 digits.
- 💬 The char data type uses two bytes and stores a single character, letter, or ASCII value.
- 📝 The String data type is a reference type that stores a sequence of characters, such as words or sentences.
- 🔑 Primitive data types store data directly, use less memory, and are faster, while reference data types store an address and use more memory.
Q & A
What is the primary function of a variable in Java?
-A variable in Java acts as a placeholder for a value, and it behaves as the value that it contains, similar to how variables are used in algebra.
What are the eight primitive data types in Java?
-The eight primitive data types in Java are boolean, byte, short, int, long, float, double, and char.
What is the significance of the boolean data type in Java?
-The boolean data type in Java can only hold two values, true or false, and is typically used for binary conditions.
What is the range of values that can be stored in a byte data type in Java?
-A byte data type in Java can hold integer values between -128 and 127.
What is the difference between the int and long data types in Java?
-The int data type uses 4 bytes of memory and can store values up to just over 2 billion, while the long data type uses 8 bytes and can store much larger values, up to just over positive nine quintillion.
Why is the float data type used in Java?
-The float data type is used in Java to store fractional numbers with a precision of up to six to seven digits.
What is the main difference between float and double data types in Java when assigning values?
-When assigning values to a float variable in Java, the value must be followed by the letter 'f', whereas for a double variable, no such suffix is needed.
What is the purpose of the char data type in Java?
-The char data type in Java is used to store a single character, letter, or ASCII value, and requires single quotes around the value when assigning.
How does a string data type differ from primitive data types in Java?
-A string is a reference data type in Java, which means it stores a sequence of characters and uses more memory compared to primitive data types that store a single value with less memory.
What is the process of creating a variable in Java?
-To create a variable in Java, you first declare the data type and variable name, then you can either assign a value to it separately or combine the declaration and assignment in a single step called initialization.
How can you print the value of a variable in Java?
-In Java, you can print the value of a variable using a print or println statement, making sure not to enclose the variable in quotes unless you intend to print a string literal.
Outlines
📘 Introduction to Variables in Java
The video script introduces the concept of variables in Java, comparing them to algebraic placeholders but with the added complexity of storing various data types, including numbers, words, sentences, and boolean values. It emphasizes the importance of declaring a variable's data type before use and introduces Java's eight primitive data types and the reference data type 'String'. The script explains the significance of data types for memory usage and performance, highlighting 'boolean' as a one-bit data type that can only hold true or false, and 'byte', 'short', 'int', 'long', 'float', 'double', and 'char' with their respective memory sizes and ranges of values they can store. The video promises to guide viewers through understanding and using these data types in Java programming.
🔢 Understanding Data Types and Variable Creation
This paragraph delves deeper into the specifics of Java's data types, explaining the differences between primitive and reference data types. It details the process of creating a variable, which involves declaring the data type, assigning a value, or initializing the variable with a value in one step. The script provides examples of creating and using integer, long, float, and double variables, including the conventions for assigning values to float variables with an 'f' suffix and the precision differences between float and double. It also touches on the use of bytes, shorts, and the limitations of their storage capacities, suggesting that integers are more commonly used for beginners. The paragraph concludes with an example of printing variable values to the console, demonstrating how variables behave as the values they contain.
🔤 Exploring Boolean, Char, and String Data Types
The final paragraph of the script covers the remaining data types: boolean, char, and string. It explains the boolean data type's ability to hold only true or false values and the convention of printing boolean values. The char data type is introduced as a two-byte data type that stores a single character, with an example of creating a variable named 'symbol' and assigning it the '@' character. The paragraph also discusses the string data type, a reference type that can store sequences of characters, and contrasts it with char by demonstrating string concatenation with variable names and literals. The script concludes with an invitation for viewers to access the code examples in the comments and encourages them to like, comment, and subscribe to support the channel.
Mindmap
Keywords
💡Variable
💡Data Type
💡Boolean
💡Byte
💡Integer
💡Long
💡Float
💡Double
💡Char
💡String
💡Primitive vs. Reference Data Types
Highlights
Introduction to variables in Java as placeholders for values.
Comparison of variables to algebraic values like x or y.
Explanation of variables storing not just numbers but also words, sentences, and boolean values.
The necessity of declaring the data type when storing a value in a variable.
Introduction of Java's eight primitive data types and the special reference data type String.
Detailed explanation of the Boolean data type with its binary true or false values.
Byte data type's capacity to hold integer numbers between -128 to 127.
Short data type's ability to store larger numbers with two bytes of memory.
Integer data type's use of 4 bytes to store numbers up to just over 2 billion.
Long data type's capability to hold extremely large numbers with eight bytes of memory.
Float data type's storage of fractional numbers with less precision than a double.
Double data type's precision in storing fractional numbers up to 15 digits.
The unique convention of appending 'f' to float variable assignments.
Char data type's use of two bytes to store a single character or ASCII value.
String data type's variable size for storing sequences of characters.
Differences between primitive and reference data types in terms of storage, memory usage, and speed.
Process of creating a variable through declaration, assignment, and initialization.
Demonstration of printing variable values to the console window.
Use of long data type for extremely large numbers with the 'L' suffix.
Explanation of the float and double data types for fractional numbers without and with higher precision.
Boolean data type's limitation to true or false values only.
Char data type's requirement of single quotes for character assignment.
String data type's use of double quotes and demonstration of string concatenation.
Offer to provide all example code in the comments for further learning.
Transcripts
hey how's it going everybody it's your
bro hope you're doing well and in this
video i'm going to teach you guys all
about variables in java so
sit back relax and enjoy the show
if you find this video helpful please
remember to like
comment and subscribe your support will
help keep this channel running
all right guys and gals let's talk about
variables
now a variable is a placeholder for a
value
and it behaves as the value that it
contains do you remember from either
elementary school or middle school when
we were working with
algebra we usually had to solve for some
sort of variable like
x or y and x or y contained
some sort of numeric value and for all
intents and purposes
this variable behaved exactly as this
value
well with programming we can perform
something similar to that
but we are not limited to just numbers
we could also store
words whole sentences and these things
called boolean values which hold either
true or
false but if we're going to store a
value within a variable
we have to list the data type of what
we're planning to store within
that variable is it going to be a number
a word
a boolean so we need to discuss data
types
there are eight primitive data types and
a special
reference data type called a string
anything that i have noted with a star
is particularly important
so i would pay special attention to
these our first data type
is boolean this has a size of one
bit so it can only hold two values that
being
true or false if we're attempting to
sign a boolean value
we would type either equals true or
equals false
something similar would be let's say we
have a light switch program
well if the light switch is on we could
say that the light switch has a value of
true if it's off
it has a value of false so this is
binary that's why it only uses
one bit it only needs one bit of memory
to function
next we have byte this isn't as
important as a few others
but with one byte we can hold an integer
number between negative 128 to 127
because a byte only has one byte of
memory
a short has two bytes of memory so can
hold a
larger number between negative 32 000
and some change
to 32 000 and some change so integers
integers are important these use 4 bytes
of memory
and they can store a number to just
under 2 billion
to just over 2 billion because they use
4 bytes of memory and a long
they use eight bytes of memory so they
can hold a very
large number in fact they can hold a
number between
just under negative nine quintillion to
just over
positive nine quintillion now a float
they can store a fractional number
specifically
up to six to seven digits what makes
floats different from
these data types on the top here is that
bytes shorts integers and longs can only
store a whole
integer they cannot store this decimal
portion
so if you're working with a program or a
variable
that uses a fractional number you'll
need to use either a float
or a double and a double has more
precision it uses eight bytes of memory
and it can store a fractional number up
to 15 digits
so in comparison with a float this has
less precision
than a double and for an example i just
listed a few of the digits of pi
with this example we can only store six
to seven digits of pi but with a double
we can store up to 15. there is one
strange convention with floats if you're
going to assign a value to a variable
that's of the float data type you need
to follow the value
with the letter f with double variables
you actually do not need to do so
so that's one major difference when
assigning values between
these two now let's move on to
characters pronounced
char for short think of charizard this
uses two bytes of memory
and this will store a single character
letter or ascii value
an example would be the letter f but a
common convention with
assigning values to a char variable is
that you need to surround
this value with a pair of single quotes
and our last data type is the string
data type the size really varies because
these are
reference data types they store a
sequence of characters
like a word or a sentence you could
store a single character within a string
but chars and strings behave differently
because
chars are primitive data types and
strings are reference data types
so let's distinguish the difference
between primitive and reference data
types
here's a super quick description between
the differences of primitive
and reference data types primitive data
types there are it and we
just discussed them they are boolean by
short integer longs
all those cool things that we just
discussed reference data types
like strings well there's an unlimited
amount because
they are user defined primitives store
data reference data types store an
address
primitives can only hold one value
reference data types could hold more
than one value
primitives use less memory compared to
reference data types
which use more memory and primitive data
types are faster compared to reference
data types
which are slower now you're probably
thinking cool story bro but how do we
create a variable
well i'm glad you asked that question so
the first process with
creating a variable is that we need to
declare
the data type of what value that this
variable is going to store
so come up with a variable name like x
and we will precede this variable with
the data type of the value that we're
planning to store within
this variable and then with all
statements we follow this
with a semicolon at the end the next
step
is called assignment we will take our
variable and assign it equal
to some sort of value of the data type
that we declared this variable to be
but you could combine steps one and two
together
and this process is called
initialization
we would take the data type followed by
the variable name and set it equal to
some value and then add a semicolon at
the end to finish the statement
so you can either do this in two steps
with declaration and assignment
or combine them both together which is
initialization
how about we create a few variables does
that sound good to you guys so let's
begin with creating an
integer variable let's say int x
this step is called declaration we are
declaring the data type
of what value is going to be contained
within this variable the second step
is called assignment we can assign our
variable a value
let's say x equals 123 and
this step is called assignment or
we could combine both of these steps
together and this process is called
initialization intex equals 123
and this would be initialization
so we can do stuff with this variable it
will behave as the value that it
contains
we could print this to the console
window so within a print or print line
statement
we could print the value of x so make
sure you do not write this within quotes
right now this will display the value
that is contained within x
which is 123 because this variable
behaves as the value that it contains if
you were to surround this with quotes
what we are doing now is printing a
string literal
you can also print text as well as a
variable together
let's say we have a sentence a string
literal that states
my number is
and then if we want to do some string
concatenation with a variable
we would add plus and then the variable
name make sure this is not within quotes
so this will display the sentence my
number is plus our variable
and in the console window it states my
number is 123. so with integer variables
the largest number that you can store
within an integer variable
is just over 2 billion let's say we are
working with an extremely large number
like the amount of student debt that i
owe well this number is too large to
store it within an integer variable
we would probably want to use the long
data type
and one convention with assigning values
to a long
variable is that you need to follow this
number
with a capital l for some reason so we
can now work with extremely large
numbers
so this might be useful if you're
working with numbers like the speed of
light or something
so we now have a long variable and we
can display
this value a few of the other data types
that we mentioned were
bytes and shorts they have a lesser
number that they can store
so with bytes you can only store up to i
believe 127
so we could store like 100 within here
and this would be fine but 130 would
be a little too much though so we don't
tend to use bytes and shorts too much as
a beginner because it's just way more
convenient to work with integers
um but you might use longs every once in
a while too but
as beginners we're mostly going to be
sticking with integers
now a double can store a number with a
fractional portion with integers we
cannot store
a decimal portion so if this was 123.01
well we cannot store this decimal
portion
we can only do so with a float or a
double
so with a float you would type in float
for the data type let's create a new
variable like
y float y equals 3.14
and a common convention for assigning
numbers
well values to float variables is that
you have to follow this
with f so you can store
a number with a decimal portion within a
float
or a double and then we could display
whatever this value is
so y is equal to 3.14
but people tend to use doubles more
because they have more precision
and then you do not need this f at the
end
so this will store up to 15 digits after
the decimal portion
so we also have booleans let's say
boolean
z equals this holds either true
or false and then we can display
what value is within this boolean so if
we print
our variable z this will display false
or we could hold true and this will
display
true but we can't display anything else
besides those two
like we cannot hold the word pizza
because booleans only hold
true or false we have characters
char for short char and we don't
necessarily need to
come up with a variable that's only one
letter we could have a name or something
that's descriptive for this
let's say we have a variable called
symbol
char symbol equals and then place
a character within single quotes let's
say we
want the at sign so we now have
a variable called symbol that contains
the at sign
so if i were to display this variable
symbol to the console window
it will display the value that is
contained within which is the at sign
and lastly we have strings so with
strings these start with a capital s
because they are of the reference
data type anything that's a reference
data type begins with a capital letter
and let's say we want to store our name
so string is the data type
let's say the variable name is name
equals
and to store a string it works similar
to a string literal
we're going to use a set of double
quotes and display
or add a bunch of text like my name
and then i can now display my name to
the console window
or i could do some string concatenation
too and display
the word hello plus my name
and within the console window it's now
going to display hello
bro so that is everything you need to
know to get started with
variables in java if you would like a
copy of all this code i will post all of
this in the comments down
below don't be afraid to smash that like
button
drop a comment down below and subscribe
if you'd like to become a fellow bro
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