Variables in Java ✘【12 minutes】

Summary

This 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

00:00

📘 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.

05:00

🔢 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.

10:01

🔤 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.

Keywords

💡Variable

A variable in programming, as described in the video, is a placeholder for a value. It's fundamental to the theme of the video, which is teaching about variables in Java. Variables can hold different types of data, such as numbers, words, or boolean values. For example, the script mentions using a variable to represent a light switch's state, which can be either 'true' or 'false'.

💡Data Type

Data types define the kind of data a variable can hold, such as numbers, characters, or boolean values. The video emphasizes the importance of declaring a data type when creating a variable in Java. For instance, the script explains that integers, which are a data type, can store whole numbers within a specific range.

💡Boolean

Boolean is a data type that can only hold two values: 'true' or 'false'. It's a key concept in the video, used to illustrate the simplest form of data a variable can hold. The script uses the example of a light switch program to explain how a boolean variable can represent the on or off state of the switch.

💡Byte

A byte is a data type that can hold an integer number between -128 and 127. It's mentioned in the script as one of the less commonly used data types due to its limited range, but it's important for understanding the variety of data types available in Java.

💡Integer

Integer is a data type that uses 4 bytes of memory and can store numbers ranging from just under -2 billion to just over 2 billion. The video uses integers to demonstrate a commonly used data type for storing whole numbers in Java.

💡Long

Long is a data type that uses 8 bytes of memory and can hold very large numbers, from just under -9 quintillion to just over 9 quintillion. The script mentions using a long data type to store extremely large numbers, such as the speed of light, emphasizing its capacity for large-scale calculations.

💡Float

Float is a data type used to store fractional numbers with a precision of up to six or seven digits. The video explains that floats are different from integer data types because they can store decimal portions, and it uses the example of storing a value like 3.14 with a float variable.

💡Double

Double is a data type with higher precision than float, capable of storing fractional numbers with up to 15 digits of precision. The script contrasts double with float, noting that double does not require the 'f' suffix when assigning values, and can store more precise numbers like a longer sequence of digits for pi.

💡Char

Char, short for character, is a data type that uses two bytes of memory to store a single character, letter, or ASCII value. The video script uses 'char' to illustrate how to store a single character in a variable, such as the '@' symbol, and how to display it.

💡String

String is a reference data type used to store a sequence of characters, such as words or sentences. The video explains that strings are different from primitive data types because they store an address rather than the actual data. The script demonstrates how to declare, initialize, and use string variables to store and display text.

💡Primitive vs. Reference Data Types

The video script distinguishes between primitive data types, which store data directly and use less memory, and reference data types, which store an address to the data and use more memory. This distinction is crucial for understanding how variables work in Java and the performance implications of using different 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