Learn Java in One Video - 15-minute Crash Course

Summary

In this informative video, John, a seasoned Java programmer, empathizes with beginners' struggles and shares his journey from confusion to expertise. He guides viewers through setting up an IDE, writing basic Java programs, understanding variables, and utilizing methods. John introduces object-oriented programming concepts, explaining classes, objects, and static vs. non-static methods. His aim is to simplify Java, offering a comprehensive course for deeper insights and encouraging questions for further assistance.

Takeaways

• 😀 The speaker empathizes with those struggling to learn Java, emphasizing that it's a common experience and not to feel alone.
• 📚 The speaker introduces himself as John, a seasoned Java programmer who aims to share knowledge in an understandable way.
• 💻 It's necessary to install an IDE (Integrated Development Environment) like Eclipse to write Java programs more efficiently.
• 🛠️ Eclipse is used to write Java programs and automatically translate them into bytecode, a format the computer can understand.
• 📝 The process of creating a Java program in Eclipse involves creating a new project and class, with the main method being the starting point for code execution.
• 🔢 Variables in Java are used to store data and consist of a name, type, and value, with 'int' being an example of a primitive type.
• 📑 The 'main' method is where most of the coding happens, and the code within its curly brackets defines what the program does when run.
• 🔠 Java has eight primitive types, including 'int' for integers, 'double' for decimal numbers, and 'char' for characters.
• 🔑 Non-primitive types like 'String' are used to hold text and offer various methods for manipulation, such as 'length()' and 'toUpperCase()'.
• 🔄 Methods in Java can be created by the programmer to bundle functionality and avoid code repetition, and can take parameters and return values.
• 🔒 Conditional statements like 'if-else' allow for decision-making in programs based on conditions, using '==' for equality checks.
• 🔁 Loops, such as 'for' loops, enable repeated execution of code segments, with the loop's condition controlling the number of iterations.
• 🐱 Java is object-oriented, allowing for the creation of classes as blueprints for objects, which can have attributes and behaviors defined by the class.
• 📌 The 'static' keyword in Java methods means they can be called without creating an object instance, while non-static methods require an object.

Q & A

What does the speaker struggle with in the beginning of the script?

The speaker struggled with understanding basic concepts of Java and felt overwhelmed in their first Java class in college.

What is the purpose of an Integrated Development Environment (IDE)?

An IDE is a program that makes it easier to write code, similar to how Microsoft Word makes it easier to write school papers.

What is the name of the IDE used by the speaker in the video?

The speaker is using an IDE called Eclipse.

What does the speaker suggest to install before starting to code in Java?

The speaker suggests installing an IDE and possibly other tools, mentioning that the process is super easy and only takes a few minutes.

How does the speaker describe the process of creating a new Java project in Eclipse?

The speaker describes creating a new Java project by right-clicking in the Package Explorer, selecting 'New Java Project', giving it a name, and clicking 'Finish'.

What is a 'class' in Java according to the script?

A 'class' in Java is essentially a Java file, which is a fancy name for a container of code and functionality.

What is the significance of the 'main' method in Java?

The 'main' method is significant because it is the entry point of a Java program, containing the code that runs when the program is executed.

What is a variable in Java and what are its components?

A variable in Java is used to store data and has three components: a name, a type, and a value.

What is the difference between primitive and non-primitive types in Java?

Primitive types are the most basic types in Java, indicated by a lowercase letter, such as 'int' for integers. Non-primitive types are built on top of these and include more complex structures like 'String'.

How can you interact with a non-primitive type like 'String' in Java?

You can interact with a non-primitive type like 'String' by calling its methods, such as 'length()' to find the length of the string or 'toUpperCase()' to convert the string to uppercase.

What is a method in Java and how is it used?

A method in Java is a block of code that performs a specific task. It is used by declaring the method with a name and then calling it by that name within the code, potentially with parameters and a return type if necessary.

What is the role of 'static' in methods and classes in Java?

The 'static' keyword in Java means that the method or class can be called without creating an instance of the class. It is associated with the class itself rather than instances of the class.

How does the speaker explain the concept of object-oriented programming in Java?

The speaker explains that object-oriented programming in Java involves creating classes as blueprints for objects, which can then be instantiated with specific attributes and behaviors.

What is the purpose of conditional statements in Java?

Conditional statements in Java are used to perform different actions based on whether certain conditions are true or false, using 'if', 'else if', and 'else' clauses.

How are loops used in Java to repeat code execution?

Loops in Java, such as 'for' loops, are used to repeat code execution multiple times without copying and pasting the same code. They are controlled by initializing a variable, a condition to continue the loop, and an increment or decrement operation.

What is the speaker's final recommendation for those interested in learning more about Java?

The speaker recommends a full Java course available in the description of the video for those who want to go into more depth on various topics of Java.

Outlines

00:00

📚 Java Learning and Setup Essentials

The speaker empathizes with the struggles of learning Java, sharing personal experiences and offering help. The paragraph introduces the speaker, John, who has been programming in Java for 10 years and plans to share knowledge in an understandable way. It covers the basics of setting up Java development, including installing an IDE like Eclipse, which simplifies the coding process. The video also guides viewers on creating a Java project and class in Eclipse, explaining the significance of the 'main method' and how to write a simple program that prints variable values. The importance of variables, their types, and values are discussed, along with how to perform operations like multiplication and store results in new variables.

05:02

🔍 Exploring Variables, Methods, and Conditional Logic in Java

This section delves deeper into Java variables, explaining primitive types like 'int', 'double', and 'char', and their usage. It demonstrates variable interaction through example calculations and the assignment of results to new variables. The paragraph introduces non-primitive types, particularly 'String', and discusses methods associated with them, such as 'length' and 'toUpperCase'. The concept of creating custom methods in Java is introduced, explaining how methods can be used to avoid code repetition and can take parameters and return values. Conditional statements and loops, such as 'if', 'else', and 'for', are also explained, showing how they can be used to control program flow based on conditions and repeat code execution.

10:03

🐱 Object-Oriented Programming with Java Classes and Objects

The final paragraph introduces the core concept of object-oriented programming in Java, focusing on classes and objects. It explains how to create a separate class, such as 'Cat', and use it as a blueprint to create objects with unique attributes and behaviors. The paragraph demonstrates creating class methods, both static and non-static, and the difference between them in terms of accessibility and usage. It also illustrates how to set and use properties of objects, like name and age, and calls methods on them. The video aims to clarify the use of 'static' in methods and the overall object-oriented approach to structuring Java programs, offering a foundation for more complex Java applications.

Keywords

💡Java

Java is a high-level, class-based, object-oriented programming language designed for portability and versatility. In the video, Java is the central theme, as the speaker discusses his experience learning Java and offers guidance to beginners. The script mentions Java in the context of programming concepts and the tools needed to write Java programs, such as an IDE (Integrated Development Environment).

💡IDE (Integrated Development Environment)

An IDE is a software application that provides comprehensive facilities to computer programmers for software development. In the script, Eclipse is introduced as the IDE being used to write Java programs, highlighting its role in simplifying the coding process and converting code into bytecode that computers can execute.

💡Variables

Variables are used in programming to store data. The script explains that variables have a name, a type, and a value. For example, 'int myInt = 7;' creates a variable named 'myInt' of type 'int' (integer) with a value of 7. Variables are fundamental to Java programming, allowing data manipulation and storage throughout the script.

💡Main Method

The main method is the entry point of a Java program. It is defined with 'public static void main(String[] args)' and contains the code that runs when the program is executed. The script describes the main method as the place where most of the coding happens, illustrating its importance in Java programming.

💡Primitive Types

Primitive types in Java are the most basic data types and include 'int', 'double', 'char', etc. The script mentions 'int' for integers, 'double' for decimal numbers, and 'char' for characters. These types are essential for understanding data representation in Java and are used to define variables with specific data storage capabilities.

💡String

A String in Java is a sequence of characters used to store text. The script demonstrates creating a String variable with 'String myName = "John";'. Strings are non-primitive types and are used extensively in Java for handling text data, as shown in the video where methods like '.length()' and '.toUpperCase()' are applied to String objects.

💡Methods

Methods in Java are blocks of code designed to perform a specific task. The script introduces methods with 'private static void burp()' as an example. Methods can be called to execute their code, and they can also take parameters and return values, which is crucial for reusing code and modular programming.

💡Conditional Statements

Conditional statements are used to perform different actions based on different conditions. The script uses 'if', 'else if', and 'else' to demonstrate conditional logic, such as 'if (name.equals("John"))'. These statements are vital for decision-making in Java programs.

💡Loops

Loops are used to execute a block of code repeatedly. The script explains 'for' loops with an example that prints a phrase multiple times. Loops are essential for iterating over data and performing repetitive tasks without duplicating code.

💡Object-Oriented Programming (OOP)

OOP is a programming paradigm based on the concept of 'objects', which can contain data in the form of fields and code in the form of methods. The script touches on OOP by discussing creating a 'Cat' class and objects from that class, emphasizing the use of classes as blueprints for creating objects with specific attributes and behaviors.

💡Static

The 'static' keyword in Java is used to create class-level methods or variables that are not tied to any specific instance of the class. The script mentions 'static' in the context of the 'dingDong()' method, which can be called on the 'Cat' class itself without needing a 'Cat' object. This is contrasted with non-static methods like 'meow()' that require an instance of the class to be called.

Highlights

The speaker empathizes with those struggling to learn Java, emphasizing that they are not alone.

John, the speaker, shares his personal experience of struggling with Java in college but now has 10 years of experience.

The importance of installing an IDE like Eclipse for writing Java programs is discussed.

Eclipse is introduced as the IDE used for writing and translating Java programs into bytecode.

A step-by-step guide on creating a Java project and class in Eclipse is provided.

Explanation of the 'main method' in Java and its role in running a program.

Introduction to variables, their types, and values in Java with examples.

The concept of primitive types in Java and their characteristics is explained.

Demonstration of how to perform operations like multiplication on variables and store results.

Introduction to non-primitive types like 'String' and their usage in Java.

Explanation of methods, how to call them, and their functionality in Java.

The process of creating custom methods in Java and their purpose is outlined.

Parameters and return values in methods are introduced with examples.

Conditional statements and their syntax in Java are explained with examples.

The concept of loops, specifically 'for loops', and their use in Java is discussed.

Java's object-oriented programming nature and the use of classes as blueprints for objects.

Creating objects from classes and setting their attributes like name and age.

The difference between static and non-static methods in Java and their usage.

John offers further help for any Java questions in the comments and provides a link to a full Java course.

Transcripts

if you're struggling learning java i

understand how you're feeling it can

feel like everyone around you is some

kind of programming genius who just gets

everything with no problem at all and

you feel like you must be the only one

having trouble with it you're absolutely

not alone and you're in the right place

i remember in my first java class in

college i really struggled to understand

some of just the basic concepts and

really just felt overwhelmed but now

i've been programming in java for a

living for the past 10 years and i want

to make sure you don't have to struggle

the same way i did my name's john and i

love sharing what i've learned about

java in a clear and understandable way

so please consider subscribing if you'd

like to see more helpful java videos in

this video we'll go over everything you

need to know to get started writing

great java programs before you can code

anything in java there's a couple of

things you have to have installed if

you've already done that awesome and if

not it's super easy it just takes a few

minutes i have a video here going

through the whole process one of the

things you'll want to install is called

an ide and integrated development

environment and that's what i have open

here the name sounds really complicated

but it's basically just a program that

makes it easier to write code kind of

like microsoft word makes it easier to

write school papers here the ide that

i'm using is called eclipse basically

we're going to write our java programs

here in eclipse and then it is going to

take our programs and automatically

translate them into a format the

computer can understand something called

byte code you know essentially the ones

and zeros that make the computer happy

and it's going to run it when you open

eclipse to get started creating a java

program just right click here in this

area called uh the package explorer and

go to new java project you can give it

whatever name you want we'll just call

it a project pineapple you can uncheck

this module thing down here we don't

need that and click finish you can see

it created our project for us here

project pineapple then you can expand

this drop down and right click this src

folder here which stands for source and

go to new class a class is basically

just a fancy name for a java file give

that name to whatever you want like

awesome java program and you want to

check this box down here that says

public static void main string args

we'll talk a little more about what that

means later then click finish and then

eclipse will automatically generate this

kind of framework for a working java

program for you now all of these

programming looking terms and keywords

might feel really intimidating but

really all this is saying is hey java

i've got this new program called awesome

java program and when i tell you to run

here's all the stuff that i want you to

do this whole section here is what we

call the main method and all the

commands we put in between these two

curly brackets in the main method are

what it's going to do when we tell it to

run so that's where we're going to be

writing most of our code this line here

with the two slashes is just an

automatically generated thing that we

don't need so we can just get rid of it

just about everything we'll do in java

revolves around creating and using

things called variables variables are

just used to store data so here's an

example and myint equals seven now

variables have a name a type and a value

for this variable int is the type it

stands for integer int is basically just

a number this my int is the name of the

variable we can give it whatever name we

want and this equals seven here is

giving this my into the value of seven

so this just says hey java i have a

number here i want to call it myant and

please give it the value of seven to

start out with and then we have this

semicolon in java most lines will end

with a semicolon it's just telling java

that's the end of the statement now

anywhere after that line in our program

we can get the value stored in that

variable just by using its name for

example if we want to just print it out

the command to print something out in

java is system.out.println

and in parentheses we specify the name

of that variable myant and we end with a

semicolon and we can click save and then

click run to run our program and we see

our output of the program here in our

console so it just prints out the value

of this my int variable which is seven

int isn't the only type of variable we

can create for example if you want to

create a decimal number you can use

double let's say we want to make a shoe

size double shoe size equals 9.5 if you

want to store a character you can use

the char type char my initial equals j

that'll be in single quotes a lot of the

magic encoding happens when we take

these variables and have them interact

with each other so we can take this

mayan variable and multiply it by the

shoe size if we want in java to multiply

you just use star so my int times shoe

size save and run it we see that we get

the result 66.5 which is 7 times 9.5 and

also instead of just printing out that

result you can actually store the result

of that calculation in another variable

so we can say double result equals my

int times shoe size all of these types

so far and double and char those are

called primitive types in java there are

eight primitive types total in java and

i have a video going over all of them

and how to use them in detail here

primitives are like the absolute basic

types in java like the sticks and stones

you'll know it's a primitive type in

java if it starts with a lowercase

letter every other type you use in java

is built on top of these primitive types

but there are tons of other types you

can use and you can even create your own

like we'll see later probably the

non-primitive type that you're going to

use most is called string string

variables are used to hold text string

my name equals john for strings you put

them in double quotes instead of single

quotes you can tell that string is not a

primitive type because it starts with a

capital s and also the primitive types

have a different coloring in eclipse

than other types do when you create a

non-primitive variable like this there's

also even more stuff you can do with it

that can be different for each type to

see what you can do with the variable if

you're using a fancy ide like eclipse

you can start out by just typing the

variable name then type a period and

you'll immediately see all the cool

things you can do with this variable

these are all called methods and when we

use any of them it's called calling a

method as you're scrolling through these

you can click one and you'll get a

description of what that method does for

example this length method says it

returns the length of this string and if

we want to use it we just double click

it or you can also just type it out if

you want to so if we move this down here

so we can print out the result of this

method call it prints out four because

john the value of the my name variable

is four characters long but there are a

ton of other methods available like for

example there's one called a two

uppercase and if we use that it gives

you an all uppercase version of that

string and if you already have the

method out here in your code and you

want to remind yourself what it does you

can just hover over the method name and

a little pop-up will appear with the

description one thing you can't do is

you can't call a method on a primitive

variable like my interior if i try to do

my int dot nothing pops up it just

doesn't work speaking of methods you can

also create your own to create a new

method here in the same java file i'll

type it out first and then we'll talk a

bit about what it means private static

void burp this whole line here is called

the method declaration and this part

right here before the parentheses is the

name of the method here we called it

burp and any code that we put between

these two curly brackets is what it's

going to do when this method is called

let's just have it print out

burp but if we go ahead and save and run

our code now nothing happens nothing's

printed out why is that that's because

if you remember when we run our java

program java just runs everything that

we put inside our main method and right

now there's nothing in here that calls

this other method that we created so

let's change that now if we want to call

this method all we have to do is use its

name burp and we also need an open and

close parentheses whenever you see this

open and close parentheses you'll know

that it's a method being called now if

we save and run our program successfully

burps so now we can have our program

burp whenever we want just by calling

burp of course a method can be a whole

lot more complicated than this and a big

reason to make a method is because you

might have a whole big complicated chunk

of code that you don't want to repeat

package it up in a method and you can

just call it as many times you want from

anywhere in your code just by using its

name now a method can also take what is

called parameters so for example if this

method was called print name between

these two parentheses is where you would

put the parameters let's say it had a

string parameter that was called name

and then just printed out my name is

plus name this plus is how you link two

strings together in java that's called

concatenating strings but now when you

call this print name method you have to

pass in a value for that name parameter

and you pass in that value by putting it

between these two parentheses uh john

and we can run it and see that it prints

out my name is john you can even take

multiple parameters if you want just

separate them by commas so i can also

take in like int number and when you're

calling it you just do the same thing

you just separate the values that you're

passing in with a comma if you want you

can also have your method return a value

right here in the method declaration

where we have this void void means it's

not returning any values but if you want

it to return a value this is where we

specify the type of the thing that it's

going to return so if we want it to

return a string we can just change this

to a string but now we have to actually

return a string somewhere in our method

so what we can do instead of just

printing out my name is blah we can just

change this to return

that value my name is blah the code that

calls this can do whatever it wants with

the string that's returned for example

we could just print it out ourselves

here or if we want since this returns a

string we can actually save that

resulting value in our own string

variable so string name equals the

result of this method call one of the

most useful things you'll ever use in

java is called conditional statements

that's your basic if this then that

conditional statements in java will look

like this if whatever condition we put

in here is true run this stuff otherwise

if whatever condition we put in here is

true run this stuff and if neither one

of those are the case run this and you

don't necessarily need all three pieces

for this you might just have an if you

might just have an if else you don't

need all three so what kind of

conditions can we have in here so we

could say like if name equals john then

print this guy is awesome else if the

name equals larry this guy is okay i

guess and if it's not john and not larry

prince i don't know this guy at all this

example uses strings as its conditions

but if you want to use the like a number

as the condition you can do things like

if number

double equals five in java you use

double equal to check equality like this

that's because the single equals is

already being used for assigning values

to variables so just remember to use

double equals but with numbers you don't

always just have to check for equals you

can do other things like if the number

is greater than 5 or less than 5 or if

you want to say if the number is not

equal to 5 you use exclamation point

equals next if you want to be able to

repeat a piece of code a whole bunch of

times without actually copying and

pasting the same code over and over and

over again you can use what's called a

loop one type of loop in java is a for

loop and it looks like this and i equals

0 i less than 10 i plus plus what this

will do is run everything inside these

curly brackets 10 times how it does that

is it declares this variable i and says

hey keep looping while i is less than

10. and every time it goes through the

loop increment i by one that's what this

i plus plus does so we can have it print

out these pretzels are making me thirsty

if we run it it'll print out these

pretzels are making me thirsty 10 times

and we can have this for loop do this

however many times we want so if we

change this 10 to a thousand and run our

program it'll print it out a thousand

times one huge thing about java is that

it's an object oriented programming

language a big part of being object

oriented is that you can take a whole

bunch of code and put it in another java

file called a class and you can use that

code in some other java file like your

main file so let's do that now we can go

over and right click on source again and

go to new class say we want to create a

cat class so we'll call it cat and you

can create a method in your class like

this public static void ding dong which

prints out ding dong this public keyword

here makes it so this method can be

called from any other java file if you

remember in our other method we used

private private makes it so this method

can only be called from within this file

that was fine because that's all we

needed it for but if you make it public

it can be used anywhere so now we can

call this cat ding dong method from our

main program like this we just say cat

dot ding dong so you can absolutely use

a separate class just like this a place

to put other methods so they don't

clutter up your main class but the main

use of a separate class like this is

actually as a blueprint to create what

are called objects so here we have a cat

class now this class itself isn't a cat

object but we can use this class to

create cat objects as many as we want

and here's how so back in our main

program we can just say cat i cat equals

new cat this creates a brand new cat

object and stores it in this variable my

cat and we can create another one if we

want so cat

another cat equals new cat right now we

haven't really put much of anything in

this cat class so our individual cats

that we've created from it can't really

do a whole lot but we can change that so

we know a cat in real life probably has

a name and an age and it can meow right

we can make our cat class like that too

so that the cats we create can do those

things so here's how we do that we just

add string name int age and we'll create

a new method public void meow that

prints meow now note that we didn't

actually set a value for the name or the

age here remember the class isn't a cat

in itself it's a blueprint for creating

cats and it tells you what kind of

attributes it has and what it can do so

what this is saying is that each

individual cat made from this class can

have a name it can have an age and it

can do this thing it can meow and back

here where we're actually creating our

individual cats that's when we can

actually set the name and age of these

individual cats my cat dot name equals

fred my cat.age equals six we use this

dot to access the fields on these

objects very similarly to how we call

methods but you'll know the difference

because when we call methods we always

have an open and close parentheses and

when we're accessing a field on that

class like name or age we don't have any

parentheses and on another cat a whole

separate cat object we can set its own

values so another cat.name equals stella

stella's age is five later on in our

program we can get those values and do

whatever we want with them so if we want

to print out fred's age later we can do

that icat dot age and it prints out six

one huge point of confusion for me

personally when i was learning java is

this whole static thing you might have

noticed in our methods sometimes we use

this static keyword and sometimes we

didn't all this static keyword means is

that this method can be called without

using an individual cat object for

example we made this ding dong method

static so back here in our main method

we could just call cat dot ding dong

notice we're just calling this method on

the clasp itself not on any specific cat

object that we created we don't need to

create a cat object first if we just

want to use this method but if it's not

static like this meow method you can

only call that method using an

individual cat object so back here

notice that i can't call

hat.meow just using the class name it

gives me an error that says i can't make

a static reference to this non-static

method but down here where i've actually

created a cat object like my cat i can

call meow on that just fine whether a

certain method that you make is static

or non-static just depends on what makes

sense for what you're trying to do of

course java is much deeper than what can

be covered in one video like this but

this should give you a ton of tools that

you can use and build off of to start

making some awesome programs i do have a

full java course available in a link

down in the description if you're

interested that goes way more into depth

on a ton of topics but if not that's

awesome too i'm just thrilled to have

you here with me my goal is really just

to help as many people as i possibly can

for real if you ever have any sort of

java questions that i might be able to

help with just put them in the comments

and i'll do my best to respond thanks so

much for watching i'm so glad to have

you here with me and i'll see you in the

next video