Help understanding Arrays and Methods

[devout epoch]

I have my final coming up and I am struggling to understand Arrays and methods still as well as how to implement them into code. Could someone help me understand these topics better so that I can use them in my code or at least understand how they work? Any help is appreciated.

[ripe grotto]

<@&987246399047479336> please have a look, thanks.

Here is an AI assisted attempt to answer your question 🤖. Maybe it helps! In any case, a human is on the way 👍. To continue talking to the AI, you can use </chatgpt:1108714622413963314>.

TJ-Bot

I have my final coming up and I am struggling to understand Arrays and methods still as well as how to implement them into code. Could someone help me understand these topics better so that I can use them in my code or at least understand how they work? An

Arrays in Java are a way to store multiple values of the same data type under one variable name. They can be of primitive types like int or double, or objects like String.

To declare an array in Java, you specify the type of elements it will hold, followed by square brackets [] and the array name. For example, int[] numbers;

To initialize an array, you can use the "new" keyword followed by the data type and the size of the array in square brackets. For example, numbers = new int[5];

Methods in Java are blocks of code that perform a specific task and can be reused throughout your program. They are defined by specifying a return type (void if no return value), method name, and any parameters it may take.

To call a method, you use its name followed by parentheses and any necessary arguments. For example, myMethod(argument1, argument2);

You can pass arrays as parameters to methods just like any other variable. This allows you to manipulate arrays within methods without modifying them outside.

To access elements in an array, you use square brackets with the index position inside. Arrays start at index 0. For example, numbers[0] = 10;

Practice writing code using arrays and methods to get more comfortable with them. You can also refer to online resources or textbooks for more in-depth explanations and examples. Good luck with your final exam!

- AI generated response

[gritty onyx]

Do you have an example that you don't understand?

[devout epoch]

I guess a specific one for methods is what does in the parenthesis in a method.
public static int Test(not sure what to put here)

for arrays I am just struggling how to set them up and how to use them in for/ while loops for example.

the final is going to have coding questions so I just want to be able to be comfortable enough to use them in any scenario if that makes sense

[viscid sandal]

think of a method as a little helper living in your program, it does a specific job and you can call it whenever you want

imagine you want a little helper on creating icecream!

here's what it would look like:

public String makeIceCream(String flavor) {
    return "Here's your " + flavor + " ice cream!";
}

we use "public" so that everyone in the program can use it (we can share it!), we use the "string" argument so that it returns a string, you see "String flavor" in the brackets? that's the constructor, you tell it what you want the flavour to be when you call the method

[ripe grotto]

Detected code, here are some useful tools:

System out

[Nothing]

[scarlet comet]

Why does my bot not work :(

[devout epoch]

so if i wanted vanilla when calling the method I would do makeIceCream(Vanilla) and the result would be "Here's your vanilla ice cream!" ?

[viscid sandal]

thing of an array as defining a variable, but instead of just having one string, integer, e.g int x = 5, we can store multiple

in other words, think of it like a tray or a box, you can store multiple objects in one box/tray

for example, let's say i have a car dealership, and i need to store all of my cars, in java i could use an array for this:

String[] cars = {"Red Car", "Blue Car", "Green Car"};

we use String as the data type and a set of "[]" to the end, to insure it's defined as an array, we then set the array name and use a set of curly brackets to store the information

[viscid sandal]

If you put that inside a variable, yeah you can print it out

or to print it out directly you could:

System.out.println(makeIceCream("vanilla"));

[scarlet comet]

The parameters are basically a variable that has the value of whatever you give it

[viscid sandal]

or

String icecream1 = makeIceCream("vanilla");

[viscid sandal]

also don't make the mistake many people do with arrays and try and print out the entire thing in one print statement,

example of a mistake:

System.out.println(cars);

this would return something like S:4744893 if I Remember correctly the "S" is the data type and the numbers is the hashcode

you would need to import the arrays class using:

import java.util.Arrays

and then print it out like so:

System.out.println(Arrays.toString(cars);

or if you cant remember the exact class you want to import, a cheat is to do

import java.util.*;

which imports everything from the "util" class

so arrays, scanners, etc

[devout epoch]

what does the .toString() do in this instance?

[viscid sandal]

toString() turns it into a string, printing out an array on its own like the mistake exampled above will return it's hashcode

it's annoying, but you have to do it

it bassically turns the haschode into human readibality iirc

it basically takes all the elements from the array and puts it in a set of square brackets

[devout epoch]

ohh ok that makes sense

another issue with methods for me is when calling I will sometimes get the error that the variable isnt established or this variable already exists. I dont know if this has something to do with passing or not but it stumps me

[viscid sandal]

i think I can understand the issue and this is most likely because you've done this:

public class Main
{
  public static void main(String[] args)
  {
     String icecream1 = makeIceCream("Vanilla");
  }

  public String makeIceCream(String flavor) {
    return "Here's your " + flavor + " ice cream!";
  }
}

[ripe grotto]

Detected code, here are some useful tools:

[viscid sandal]

this happens because the "makeicecream" method isn't static and we're calling it from a static method

you could cheat and do:

public static String makeIceCream(String flavor) {
    return "Here's your " + flavor + " ice cream!";
  }

which makes it static and would work

[ripe grotto]

Detected code, here are some useful tools:

[viscid sandal]

but it's better to create an objecft of your method

like so:

public class Main{
    public static void main(String[] args)
    {
     Main makemeIcreamCream = new Main();
     String icecream1 = makemeIcreamCream.makeIceCream("Vanilla");
    }

    public String makeIceCream(String flavor) 
    {
    return "Here's your " + flavor + " ice cream!";
    }
}

[ripe grotto]

Detected code, here are some useful tools:

[viscid sandal]

ignore the code posted earlier, forgot we were working within the same class

[viscid sandal]

Main makemeIcreamCream = new Main();

creates an instance of main

basically a better way instead of being lazy and making the "makeIceCream" method static

this code will work without issue

hopefully this makes sense

[devout epoch]

I am sorry, but I do not think we have learned about how to do what you just posted. This is the first class in my universities computer science course and they seem to be doing things differently than how you are.

[viscid sandal]

What have they covered (this is what I have done in my 9th grade computer science class)

[pallid vigil]

it does work, you just didn't asked it to call the method

[scarlet comet]

?

[viscid sandal]

(if anybody wants to read over my explinations and correct/add feel free to do so)

[pallid vigil]

what do you not understand ?

[viscid sandal]

i have attempted to explain the question in the best way i can

[pallid vigil]

this is too advanced, op merely asked how to use methods

[pallid vigil]

?

[scarlet comet]

This is basic oop

[pallid vigil]

variables only exist where you declared them

[scarlet comet]

The bot didn’t send help with my question

[pallid vigil]

?

[scarlet comet]

I send a screenshot

Normally

[viscid sandal]

they asked a follow up question about errors when using methods in a static main method

i gave two solutions

[scarlet comet]

A bot attempts to answer your question, for me it didn’t

[viscid sandal]

also please can we move this unrelated discussion out of this post i am trying to help OP

@scarlet comet

[dire fern]

lets focus on helping OP please

[scarlet comet]

Sure

[devout epoch]

the book we are using, which isnt very helpful, is Introduction to Java Programming by Y. Daniel Lang. the things we have gone over is number conversion, variables, conditionals, math, math.pow for example, strings, while and for loops, files, methods, and arrays

[viscid sandal]

HI, do you have examples of what they are covering?

[viscid sandal]

Ah okay

[pallid vigil]

wait, you are in the wrong thread

[viscid sandal]

So you are struggling with methods and arrays?

[scarlet comet]

You responded to me, but let’s move

[devout epoch]

yes and you are being very helpful I appreciate it, most I understood it was just the new stuff that threw me for a loop. I can provide some slides the professor uses if that can give you insight on my current understanding of the topic

[pallid vigil]

You started by writing a message in this thread, this is the wrong thread, please go to your thread

[devout epoch]

he kinda just reads and talks about what is on the slides, but somehow avoids explaining whats going on and how everything works

sorry if thats a lot

[pallid vigil]

then what do you not understand ?

[viscid sandal]

Let's break down this example

We have a static method here (not sure why he's using a static method) but a static method means it belongs to the class and not any objects

We have two parameters which are both integers, start and stop

We set the result variable to 0

We now have a for loop, let's break it down

The variable "i" is basically just a counter, imagine it as your fingers when you count, it will increase EACH time the for loop iterates, which means for as long as i (the counter) is less than or eual to the stop variable, it will keep going and adding the counter to the result variable

Finally we have a return statement, this will return the result variable

By iterate I basically just mean to repeat

oh and I forgot to mention that the start variable is set as the counter

[devout epoch]

how to use methods and arrays in different scenarios

[viscid sandal]

Why don't you, as a practise write a program where you are a pizzaria, make a method for making pizzas where it will take parameters such as toppings, type, and size

For arrays practise, try making an array, and then using a for loop to iterate through each index of the array and print out that index

(Remember that array indexing begings at 0 in java, e.g if an array was:

int[] numbers = {1,2,3,4,5}

Number "1" would be the "0" index

be at the*

[devout epoch]

Okay. I will post them here when I am done.

[viscid sandal]

oh and to acess a specific index you would use:

numbers[i]

[devout epoch]

This is also something I could not figure out, and there could likely be someting similar on the test. If you could walk me through it after I do the practices you provided it would help me out a lot. Thank you again for all your help.

[viscid sandal]

👍 This task is pretty hard considering the fact you don't yet fully understand arrays and methods, but I'll assist on it

let me know if you have any issues during the practises I provided!

[viscid sandal]

this problem was pretty challenging since I had to write the entire code and wasnt given some of the code to me like your professor did here

however I've solved it:

https://github.com/WildRagers/isIdentical-Problem/tree/main

if you want to take a look

[gritty onyx]

@viscid sandal please don't do peoples homework for them.

[devout epoch]

sry I forgot to mention that I had already turned in the homework before asking them that

I could not figure it out so I asked for help. Was not using the helper to get a good grade. I want to learn

I can provide the grade if need be to clear up any confusion or doubt

@viscid sandal done with the first one

[gritty onyx]

In this case you have two tasks.

1. Read the file into two arrays. The first line has the size of the arrays, and the following lines have two values, one for each array
2. Compare the two arrays - and the implementation proposed would be to loop over the first array, seeing if that value is in the second array. If all values of the first array are in the second. Since it doesn't clarify if duplicate values can exist, a complete solution would also need to check if all of the values in the second array are in the first.

Note: When getting interactive input (from a user) with Scanner, you should always use .nextLine(). Using combinations of other methods like .next() and .nextInt() can result in confusing program-flow in the event of bad input.

[devout epoch]

So just for clarification, I should use .nextLine() over the other two even when I am asking for an int or just a single word?

sorry if that is a silly question. I was taught to use .nextInt() when the user is inputting an int.

[gritty onyx]

You should use .nextLine() always... and then, if you want to try to parse that as an int use Integer.parseInt(scanner.nextLine())

I was taught to use .nextInt() when the user is inputting an int.

It's a common mistake that a surprising number of educational sources repeat.

Yes t's shorter, but it is objectively worse for user input. It only works in trivial cases and can't cope with user data-entry error.

[devout epoch]

thank you for breaking that down. I am going to implement that into practice going forward

@viscid sandal done with the second

@gritty onyx I would like to get to the point where I am confident enough with java that I could do what you and br1t are doing if asked by someone who needed help. Would that MOOC course be a good start or are there other resources here that would be better to start with?

[gritty onyx]

The MOOC is an excellent place to start.

[viscid sandal]

I had assumed by the fact that he shared the assignment and the way they talked about it, the assignment was already past due date. I also shared a GitHub link just in case they didn’t want to see it, thank you for your concern.

[viscid sandal]

Amazing work I’ll read over the code and give feedback

[viscid sandal]

Great work, have you been taught user input? More specifically the scanner class? If so you could make it so each iteration it will ask the user what they want to change the number at the index position to

[viscid sandal]

This code is good and does work however it would be better if you didn’t make every method static other than your main method, it’s good habit to get out of doing that especially when you get to the stage of calling methods from other classes

but for now it’s completely fine

[viscid sandal]

iirc you can declare the scanner in your class instead of declaring it for every method

however not on my computer atm so can’t write any code now

With these side projects in mind, do you feel more comfortable with methods and arrays?

[devout epoch]

I do actually. Maybe not enough to tackle those homeworks again yet, but I do feel like im getting there. Both you and talden have super helpful

[gritty onyx]

You absolutely should not create multiple scanners consuming the same input. You should either capture it as shared state (eg a field on an object or, reluctantly, static state) or pass the scanner to each method that needs it.

[viscid sandal]

Exactly this

[viscid sandal]

Are those the only homework assignments? Those were pretty tough even for me but im not proficient in Java

[devout epoch]

those were the only arrays homework. they tell us to use the book, but the homework is significantly more difficult compared to the examples in the book.

[devout epoch]

how would I pass the scanner to each method?

[viscid sandal]

I can try write up an example of this, give me a moment, it will take me a bit of time since im on mobile

Unless talden can write one

[viscid sandal]

learning Java for the first time?

[gritty onyx]

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    ...
    foo(in);
}

private static void foo(Scanner in) {
    System.out.print("Write something: ");
    String line = in.nextLine();
    ...
}

[devout epoch]

yes this is my first class on it

[viscid sandal]

public class MyClass {
   
    private Scanner scanner = new Scanner(System.in);

    
    public void readInput() {
        System.out.println("Enter some text:");
        String input = scanner.nextLine();
        System.out.println("You entered: " + input);
    }

    public static void main(String[] args) {
        MyClass myObject = new MyClass();
        myObject.readInput();  
    }
}

I would have come up with something like this

but I assume your way would be easier to learn

apologies if it’s formatted wrong im on mobile and i can’t embed very well

[gritty onyx]

If they haven't learnt about object state then the passing is easier. But capturing it as object state is better.

[viscid sandal]

have you taken a CS class before?

I assume not because most HS CS classes do java and AP CS is Java iirc

unless it’s different in diff systems

[devout epoch]

I have not. I recently decided to take up programming

id like to do web development

[viscid sandal]

ah okay

[viscid sandal]

wait front end or backend because Java is only really used as a backend web development tool

if you want front end you should learn html css and JavaScript really

[gritty onyx]

And a full-stack developer will learn both.

[devout epoch]

I think I will learn both just to have it under my belt, but right now I think ill focus on back end

[viscid sandal]

sounds good unless you want to do Java applets 🤣

which flopped

anyways

[gritty onyx]

Applets are no longer supported in any current browser.

They are deprecated from the Java platform as well

[devout epoch]

I gotta go for a bit, but I am going to try and redo the pizza one to have it pass the scanner to each method. thank you both again for the help yall are great

[viscid sandal]

Speaking about scanners, after that you could try modifying your array project from previously to ask the user each iteration in the for loop for a new value for the index it’s on

so each time it loops basically ask the user to set a new value

Anyways im going to go to bed, gn everybody