Stage 5 #4 Number Classes like BigInteger And Javadoc Comments
Summary
TLDRThis 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
- đ Primitive types have fixed capacity, limiting their ability to store very large numbers.
- đĄ Java provides the BigInteger class to hold arbitrarily large integers, surpassing the limits of primitive types like long.
- đŠ BigInteger is an object and a reference type since it can store numbers larger than what primitive types allow.
- đ The term 'class' in Java refers to a new type, a set of objects, and the code template for creating those objects.
- đ The BigInteger class is found in the java.math package, which includes classes for mathematical functions.
- đ§ BigInteger holds its digits in an array and keeps track of the number's sign (positive, negative, or zero).
- âïž Addition and other operations in BigInteger are handled using machine-specific classes like BigInt, depending on the JVM.
- đ The Java API documentation, or Javadoc, provides an accessible way to explore Javaâs built-in classes and methods.
- đ Javadoc comments, written in a specific format, automatically generate readable documentation directly from the source code.
- đ ïž 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
đą 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.
đ 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.
đ 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.
đ§ 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.
đ 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.
Mindmap
Keywords
đĄPrimitive types
đĄBigInteger
đĄClass
đĄObject
đĄArray
đĄSign
đĄMethod
đĄJava API
đĄJavadoc
đĄBlock tags
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
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