Stage 5 #4 Number Classes like BigInteger And Javadoc Comments

Summary

This video introduces the Java BigInteger class, which handles integers larger than what primitive types like 'long' can store. It explains the concept of reference types for arbitrarily large values, and demonstrates how Java's BigInteger uses arrays to store digits. The video also highlights how to explore the Java API to find documentation on classes and methods, including tools like Javadoc, which automatically generates documentation from specially formatted comments in code. The tutorial emphasizes how Javadoc simplifies maintaining up-to-date code documentation for developers.

Takeaways

• 📏 Primitive types have fixed capacity, limiting their ability to store very large numbers.
• 💡 Java provides the BigInteger class to hold arbitrarily large integers, surpassing the limits of primitive types like long.
• 📦 BigInteger is an object and a reference type since it can store numbers larger than what primitive types allow.
• 🔍 The term 'class' in Java refers to a new type, a set of objects, and the code template for creating those objects.
• 📂 The BigInteger class is found in the java.math package, which includes classes for mathematical functions.
• 🧠 BigInteger holds its digits in an array and keeps track of the number's sign (positive, negative, or zero).
• ⚙️ Addition and other operations in BigInteger are handled using machine-specific classes like BigInt, depending on the JVM.
• 🌐 The Java API documentation, or Javadoc, provides an accessible way to explore Java’s built-in classes and methods.
• 📝 Javadoc comments, written in a specific format, automatically generate readable documentation directly from the source code.
• 🛠️ Java developers can easily generate their own Javadoc for custom code by embedding comments and using the Javadoc tool.

Q & A

What is the purpose of using the BigInteger class in Java?

The BigInteger class in Java is used to handle integers that are larger or more negative than the maximum or minimum values that the primitive type 'long' can hold. It allows for arbitrarily large integers.

Why can't a primitive type handle arbitrarily large numbers?

Primitive types in Java have fixed sizes, meaning the compiler allocates a specific amount of memory for them. Since arbitrarily large numbers require variable memory allocation, they must be handled by a reference type like the BigInteger class.

What are the three meanings of the word 'class' as used in the script?

In the script, 'class' can mean: 1) a new type being defined, such as BigInteger, 2) the set of objects of that type, and 3) the code that serves as a template for creating objects of that type.

How does the BigInteger class manage to store large numbers?

The BigInteger class stores large numbers using an array to hold the individual digits of the number. This allows it to allocate space dynamically to handle very large values.

What does the BigInteger class use to represent the sign of a number?

The BigInteger class uses an instance variable to store the sign of the number it represents. The sign can be positive one, negative one, or zero, with special handling to ensure there's only one representation for zero.

How does the BigInteger class perform addition?

The BigInteger class uses a machine-specific class named 'BigInt' that comes with the JVM to handle addition. This approach allows the addition process to depend on the specific machine the program is running on.

What is the Java API, and why is it useful?

The Java API (Application Programming Interface) is a collection of predefined classes and methods provided by Java. It is useful because it offers detailed documentation of Java classes and methods, helping developers find and use built-in functionality efficiently.

What are Javadoc comments, and what role do they play in code documentation?

Javadoc comments are special comments in Java code that start with /** and end with */. They are used to generate documentation directly from the source code, making it easy to create up-to-date, web-friendly documentation for developers.

What is the advantage of having comments next to the code they describe?

Having comments next to the code they describe ensures that the documentation is more likely to be updated alongside the code. This keeps the documentation accurate and up-to-date, unlike documentation stored in separate files.

What steps are involved in generating Javadoc documentation from code?

To generate Javadoc documentation, you need to ensure Javadoc comments are placed directly above the code elements they describe. Then, using an IDE like Eclipse, you can go to 'Project' and select 'Generate Javadoc,' which creates the documentation in HTML format.

Outlines

00:00

🔢 Understanding Java's Primitive Types and BigInteger Class

Java provides primitive types with fixed capacities for numbers, but sometimes these limits are insufficient. In such cases, Java offers the `BigInteger` class, which allows for arbitrarily large integers. Unlike primitive types, which have fixed sizes, `BigInteger` is an object type because it needs to handle variable capacities. The paragraph also explains the three meanings of the word 'class' in Java: defining a new type, a set of objects, and the code template to create objects. The `BigInteger` class, like other Java classes, has source code that can be found and explored, though understanding all the details is not necessary at this stage.

05:02

📝 Exploring the Java API and BigInteger Class Structure

The `BigInteger` class needs to store both the number and its sign, with values for positive, negative, and zero. The paragraph highlights how the class uses an array to store large numbers digit by digit, though it is still subject to memory limitations. It also explains how `BigInteger` handles arithmetic operations like addition using a machine-specific class called `BigInt`. The Java API documentation provides a structured way to explore classes, packages, and methods. By navigating the `java.math` package, you can find the `BigInteger` class, which includes descriptions of its methods, such as the `add()` method.

📜 Understanding Javadoc and Generating Documentation

Javadoc is a tool that automatically generates documentation from special comments in Java source code. These comments, called Javadoc comments, have a specific format and must immediately precede the code they describe. The paragraph explains how these comments, which start with `/**` and end with `*/`, are used to create summaries and detailed descriptions in the generated documentation. The documentation can also include HTML for better formatting, and block tags like `@param` and `@return` can be used to provide additional details about parameters and return values.

🔧 Example: Generating Javadocs for a Battleship Game

An example from a battleship game is provided to illustrate how Javadoc comments are used in practice. The `Board` class and its methods, such as checking if there is a boat at a particular position, are documented with Javadoc comments. The process for generating Javadocs is demonstrated, showing how the tool turns comments into structured HTML files, including summaries, method details, and parameter descriptions. The generated documentation can easily be shared or published online, providing valuable reference material for developers.

🚀 Conclusion: Leveraging Java's Built-In Classes and Javadoc Tool

The video concludes by summarizing the benefits of using Java's built-in classes like `BigInteger` to manage complex tasks such as handling large numbers. It emphasizes the importance of using the Java API to explore available classes and their methods. Additionally, the power of Javadoc lies in its ability to generate up-to-date documentation directly from source code comments, ensuring that documentation remains close to the code and is more likely to stay relevant. This process simplifies maintaining and sharing accurate and comprehensive documentation.

Keywords

💡Primitive types

Primitive types in Java are the most basic data types that represent simple values like integers, floating points, and characters. The video mentions that primitive types have a fixed capacity, which means they are limited in how much data they can store. This limitation is important because it contrasts with more complex data types like BigInteger, which can store much larger values.

💡BigInteger

BigInteger is a Java class that allows for the representation and manipulation of integers of arbitrary size, which means they can be far larger than the fixed-size primitive types like 'long.' The video emphasizes how this class is useful when dealing with numbers that exceed the capacity of primitive types. It also explains that BigInteger is an object, unlike primitive types, and is part of the java.math package.

💡Class

In Java, a class is a blueprint for creating objects. The video discusses three different meanings of 'class': 1) as a new type being defined, such as BigInteger; 2) as the set of objects of that type; and 3) as the template or code that defines how to create objects. Understanding these meanings is crucial when working with complex data types in Java.

💡Object

An object in Java is an instance of a class, which means it is a concrete manifestation of the blueprint defined by the class. In the video, BigInteger is introduced as an object, emphasizing that unlike primitive types, objects like BigInteger can hold arbitrarily large values because they are reference types.

💡Array

An array is a data structure used to store multiple values in a single variable. In the context of the BigInteger class, the video explains that an array is used to store the individual digits of a number, enabling BigInteger to represent very large values. This array allows for efficient manipulation of large numbers by holding each digit separately.

💡Sign

The sign of a number refers to whether it is positive, negative, or zero. In the BigInteger class, the sign is stored as an instance variable and can have values of +1, -1, or 0. The video explains how the sign is important for correctly representing numbers, especially large ones, and ensuring there's only one representation for zero.

💡Method

A method is a block of code that performs a specific task in a class. The video introduces the concept of methods in the BigInteger class, such as the 'add' method, which allows for the addition of large integers. Methods provide functionality to the objects of a class, making them essential for performing operations.

💡Java API

The Java API (Application Programming Interface) is a collection of pre-written packages, classes, and methods provided by Java for developers to use. The video highlights the importance of the API as a resource for finding detailed documentation on classes like BigInteger. This documentation is crucial for understanding how to use Java's built-in functionality.

💡Javadoc

Javadoc is a tool in Java that generates documentation from special comments in the source code. The video explains how Javadoc comments are formatted and how the tool converts these comments into HTML documentation. This allows developers to maintain up-to-date documentation close to their code, making it easier to share and understand the functionality of their projects.

💡Block tags

Block tags in Javadoc are used to describe specific aspects of the code, such as parameters or return values. The video explains that block tags like '@param' and '@return' are used to provide additional information in the generated documentation. These tags ensure that the documentation is detailed and helpful for anyone reading it.

Highlights

Primitive types in Java have fixed capacity, so larger numbers require other classes like BigInteger.

BigInteger class in Java can handle integers that are arbitrarily large and is a reference type, unlike primitive types.

BigInteger objects are not primitive because their size can vary and the compiler can't allocate fixed space for them.

Java documentation helps developers understand classes like BigInteger, and it's useful to learn how to navigate the API.

The BigInteger class uses an array to store digits, which allows it to handle very large numbers.

The sign of a BigInteger is stored separately and can be positive, negative, or zero.

BigInteger addition relies on a machine-specific class named BigInt, which depends on the machine architecture.

Java's Application Programming Interface (API) provides detailed documentation for all classes, including BigInteger.

You can generate Java documentation using the Javadoc tool, which automatically creates HTML files from special comments in the code.

Javadoc comments have a specific format starting with /** and are placed directly above the code they document.

The first sentence of a Javadoc comment becomes the summary in the documentation, followed by a detailed description.

HTML formatting can be used inside Javadoc comments to make the generated documentation easier to read.

Block tags like @param and @return are used in Javadoc to describe parameters and return values of methods.

After writing Javadoc comments, you can easily generate the documentation through the IDE by selecting the 'Generate Javadoc' option.

The power of Javadoc comes from placing documentation close to the code, ensuring that the documentation remains up-to-date as the code evolves.

Transcripts

the primitive types for numbers are

limited so in some cases you'll need to

use

other classes that java provides this

video will show you one such class

and then how to find them the

documentation that comes with java is

useful

and there's a trick to generating that

same kind of documentation for our own

code

by definition our primitive types have

to have fixed capacity

because the compiler knows how much

space to give them

sometimes we need to be able to hold

numbers that are even bigger

or even more negative than a long can

hold

to do that java gives us a class named

big integer

that can hold integers that are

arbitrarily large

it's important to think about the fact

that

something that is arbitrarily large

would

have to be an object it has to be a

reference type

because primitive types have fixed sizes

so the compiler can allocate the space

since we need this to be arbitrarily

large

it can't be primitive

now let's think about the three meanings

of the word class when it is used in

that sentence

class can be a new type we are defining

since big integer is a class

we can declare variables to be of that

type class

can be the set of objects of that type

and finally

class can be the code that is a template

for making objects of that type

that means somewhere there is a source

file named

big integer.java that has the code that

creates big integer objects

this code is just like our code and we

can go find it

no doubt merlin's going to show that

code to you

don't let it overwhelm you the point

is just to see some real code but

certainly you don't need to be able to

write code like this

you don't even have to be able to read

most of it just wander around with her

this is the code for big integer here's

the class declaration

we should be able to find things just

like the things we put in our classes

a big integer needs to know what number

it's holding

well here's an array that's going to

hold the individual digits of our number

that's how we can get so big we can

allocate an array

to hold a lot of digits

technically it isn't totally unlimited

there is

a limit to how much memory the jvm gets

but who would need to hold an integer

bigger than that

the other thing it needs to know is the

sign of the number it's representing

that's stored in this instance variable

notice that the sign is either positive

one

negative one or zero and that if the big

integer is holding a zero the sign must

be zero that's because they don't want a

positive representation of zero

and a negative representation of zero

because there's only one of them

one thing big integers need to do is to

add let's see if we can find that to do

that i'm just going to do a

find in this website to get to the code

here it is boy that isn't what i

expected

this class is using a machine specific

class that comes with the jvm

named big int that does the addition

because how we add can depend on the

machine we're running on

the point is there are methods for what

big integers need to be able to do

wading through the code is a very

difficult way to figure out what methods

are available

the lab tells you to go out and find the

java api

which stands for application programming

interface

you should do that it looks like this

in order to navigate easily let's click

on frames

up here it shows you all of the modules

and the modules for

all the module for all of the classes

that we're going to use is java.base

now there are packages and package is

a group of classes that are related to

each other

our particular big integer class is in

java.math

if you click on that you can see the

other classes that are in that

package and if i click on big integer

it shows us the documentation for the

big integer class

so it starts with a description at the

top

of what the class is and then you can

see a summary of all of the constructors

for the class

and a summary of all of the methods for

the class

this is our add method so if i click on

that

it gives you more information about

exactly what that method does

this is the way you find the things that

java gives us for free

documentation like this might look like

it's really hard

to do to make but

there is some magic that goes on look at

this description

of the class in the javadocs

and then look at the top of the source

code

immutable arbitrary precision integers

yadda yadda

it matches so there's

there is a magic program called javadoc

that takes these special comments

from our code and generates the

documentation for us

these comments are called javadoc

comments and they have a specific format

a javadoc comment must immediately

precede

the thing that it's documenting there

can't even be an empty line between them

they start with star star and end with

star slash

inside the comment the first sentence is

what will go into the summary section of

the documentation

and then the full description will go in

the more complete section of the

documentation

if you want you can embed html

formatting in them to make the resulting

web page easier to read

in addition to the description there are

a set of block tags to add specific

kinds of details

let's look at an example to see how this

works

so this is a board class from a

battleship

game and you can see up here

right above the class this is a javadoc

comment because it starts with star

slash and ends with star and since

it's right above the declaration of the

board it's describing

that board um

and you can see there are other javadoc

comments further down here as an example

here is a a method that apparently

checks to see

is there a boat at a particular position

and you can see it has a description and

the first sentence is a summary that'll

go

in the javadocs where the summary is

and then the complete english will go in

the full description in the javadocs

and then it uses these block tags

to describe extra things so in

particular we're using the param

block tag to give a description of the

one parameter that we have

and we're using the return block tag to

describe

what exactly gets returned by this

method

once you have these kind of comments

it's really easy to generate

your javadoc comments you just go to

project

and say generate javadoc i want to do it

for this project

this source file the default package and

i'm

i haven't done all of the rest of them

i'm going to show you this particular

one

the board class and say

finish and it does a pile of work and

you see

now we have in my project there is a doc

directory

and if i looked at the root of it

here is

the root of my thing here is the class

board because that's the only one that i

did

one constructor here's a summary of my

methods and here's that boat at position

the first sentence is the description

that's here

and when i click on it the full

description is here

and the descriptions of the parameters

are here

and that's all in html files

you could publish them to the web really

easily

in this video we looked at one of the

many classes that java gives us to help

build our systems

big integer is a class which will hold

arbitrarily large integers

and you'll use it in this stages lab the

way we find these free classes is by

looking at the java api

which has detailed descriptions of them

all that type of documentation is

generated from code when we embed

special javadoc comments in our code

and we can do that with our code too

then we can use the javadoc tool

to translate those comments into

searchable documentation

the real power of this comes from the

fact that the comments are right next to

the code they describe

that makes it easy for developers to

remember to update them

so it's much more likely that the

documentation will stay up to date

when compared with documentation that is

stored in separate files

you