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[polar oriole]

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

[polar oriole]

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[swift cliff]

You call non static method in static method

Also you use not good ide

Use IneligeIdea

For student they have subscription

[cerulean karma]

I used the "add" method in my static main and it works fine

Aren't "add" and "getIn" the same types of methods?

Since they are both "public Complex"

[swift cliff]

Give more information

You use object method like static

But it only object method

Before use it you should creat instance of class which method you wanna use

[cerulean karma]

I dont get the difference between a static method and a non-static one

Since they both dont have the word "static" like public static Complex getIn or public static Complex add, aren't they both non-static?

I want to use getIn to get the user's input of a complex number

[swift cliff]

https://www.geeksforgeeks.org/difference-between-static-and-non-static-method-in-java/amp/

[cerulean karma]

I know it in theory

I am just a bit confused on applying it

Do I need to call the method through an instance?

If its not static

[swift cliff]

Yes

[cerulean karma]

I see

When I used add I called it from the instance x

x.add(y)

[swift cliff]

)

Use same for getIn()

[cerulean karma]

But that made sense since I wanted to add both of them

From which instance would I call getIn()

[swift cliff]

From any instance of Complex class

But each instance have self value in there fields

[cerulean karma]

self value?

Like that? Complex z = z.getIn();

[lofty plaza]

getIn should be static

[swift cliff]

Self double a and self double b

Also you have problem with solid

[cerulean karma]

I'm lost

[swift cliff]

Complex shouldn’t read value from console

[swift cliff]

?

[cerulean karma]

    {
        Scanner myScan = new Scanner(System.in);
        System.out.println("Enter \"real\" part");
        Double complexreal = myScan.nextDouble();
        System.out.println("Enter \"Imaginary\" part");
        Double complexim = myScan.nextDouble();
        return new Complex(complexreal,complexim);
    }```

[polar oriole]

Detected code, here are some useful tools:

Formatted code

public Complex getIn() {
  Scanner myScan = new Scanner(System.in);
  System.out.println("Enter \"real\" part");
  Double complexreal = myScan.nextDouble();
  System.out.println("Enter \"Imaginary\" part");
  Double complexim = myScan.nextDouble();
  return new Complex(complexreal, complexim);
}

[swift cliff]

Find book Full Java Rerbert Shild

[swift cliff]

Other class should read value from console, after call Complex constructor and you get instance with needed value

And if you want use “fabric” make getIn() static

You should understand design pattern

[cerulean karma]

I moved it to a seperate class

I feel like this is really simple

I just want to get the Complex that getIn() returns and save it to a variable

It's this, isnt it?

[cerulean karma]

The assignment says to make a method that reads the value

[rough nest]

U create a new Scanner everytime u call thst method

You should not do that

Make the Scanner a static field and use that, since you have to read the values in ur class itself

[cerulean karma]

a static field as in?

A seperate class

[cerulean karma]

?

[rough nest]

private static Scanner sc = new Scanner(System.in);

Outside the method obviously

[cerulean karma]

But in which class

[rough nest]

Like how methods are can be static and non static, even fields cam be both

[rough nest]

Ur Complex class

Because that is where u use ur scanner

[cerulean karma]

I am having trouble understanding what you mean by "fields"

[rough nest]

Fields meaning ur instance variables

[rough nest]

Like a and b

[rough nest]

That is a method

I said a field

[cerulean karma]

This is like my 4th lesson in java

teacher aint said nothing about either private or fields

That is why I am a bit lost here

[rough nest]

Hmmm

So according to you what are the variables a and b?

In your complex class

[cerulean karma]

the "real" and the "imaginary" part of the Complex number respectively

[cerulean karma]

Or do you mean like what type of variables they are?

It's the default variables for every new Complex Instance.

[lofty plaza]

Just make getInt static

[cerulean karma]

 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */

import java.util.*;
/**
 *
 * @author royverd
 */
public class Complex {
    
    double a;
    double b;

    public Complex(double a, double b) {
        this.a = a;
        this.b = b;
    }

    public Complex() {
        // this is empty so that we can create a new instance without a,b
    }
    /*
    public Complex add2(Complex x, Complex y){
        Complex retVal = new Complex();
        retVal.a = x.a+y.a;
        retVal.b = x.b + y.b;
        return retVal;
    }*/

    public Complex add(Complex z) {
        return new Complex(this.a + z.a, this.b + z.b);
    }

    Scanner myScan = new Scanner(System.in);
    public Complex getIn()
    {
        System.out.println("Enter \"real\" part");
        Double complexreal = myScan.nextDouble();
        System.out.println("Enter \"Imaginary\" part");
        Double complexim = myScan.nextDouble();
        return new Complex(complexreal,complexim);
    }
    
    public Complex sub(Complex z) {
        return new Complex(this.a - z.a, this.b - z.b);
    }
    //public double metro(){
    //    return Math.sqrt(Math.pow(this.a, 2) + Math.pow(this.b, 2));
    //}
    public double metro(){
        return Math.sqrt(a*a+b*b);
    }


    //public String toString() {
    //    return a + "+" + b + "i";
    //}
}

[polar oriole]

Detected code, here are some useful tools:

Formatted code

 * Click nbfs : //nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs : //nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 *  / import java.util. * ;

/**
 *
 * @author royverd
 */
 public class Complex {
 
 double a;
 double b;
 
 public Complex(double a, double b) {
 this.a = a;
 this.b = b;
 }
 
 public Complex() {
 // this is empty so that we can create a new instance without a,b
 }
 /*
 public Complex add2(Complex x, Complex y){
 Complex retVal = new Complex();
 retVal.a = x.a+y.a;
 retVal.b = x.b + y.b;
 return retVal;
 }*/
public Complex add(Complex z) {
  return new Complex(this .a + z.a, this .b + z.b);
}
Scanner myScan = new Scanner(System.in);
public Complex getIn() {
  System.out.println("Enter \"real\" part");
  Double complexreal = myScan.nextDouble();
  System.out.println("Enter \"Imaginary\" part");
  Double complexim = myScan.nextDouble();
  return new Complex(complexreal, complexim);
}
public Complex sub(Complex z) {
  return new Complex(this .a - z.a, this .b - z.b);
}
//public double metro(){
//    return Math.sqrt(Math.pow(this.a, 2) + Math.pow(this.b, 2));
//}
public double metro() {
  return Math.sqrt(a * a + b * b);
}
//public String toString() {
//    return a + "+" + b + "i";
//}
}

[cerulean karma]

This seems to work

[lofty plaza]

Make getIn static please

[cerulean karma]

I hesitate because my teacher hasn't mentioned that yet. Also I recall him doing the similar thing without it being static. I just dont wanna get ahead of myself

[lofty plaza]

It doesn't make any sense to not have it static

[cerulean karma]

I can't tell the difference if I am being honest

[lofty plaza]

Your code is currently saying
"In order to create a complex from the user, you first need to create a complex, then ask this complex to ask user input and then the complex will create a complex"

[cerulean karma]

Let me process that for a bit

[lofty plaza]

tl:dr it doesn't make sense that creating a complex is needed to ask the user and create a complex from this

[cerulean karma]

I think I see your point

I am asking the "Complex" getIn to create a new Complex out of the user inputs.

[lofty plaza]

A complex shouldn't ask the user data to create a complex

[cerulean karma]

I am unfamiliar with programming talk

When you say "A Complex" are you referring to the getIn() method?

[lofty plaza]

I am talking about a Complex object

[cerulean karma]

Oh

So you're saying I should make the scanning process completely independant and then call it when I need it for the creation of the complex number?

[lofty plaza]

Complex z = new Complex()
Complex c = z.getIn()
println(c)

It doesn't make sense that a Complex asks user input and create a complex

A Complex is a number

[cerulean karma]

I see

[lofty plaza]

Since when a number ask things to someone and since when a number creates numbers

That's why it should be static

[cerulean karma]

So you're saying to create a new java class for the scanner then

[lofty plaza]

Either that or make them static

[cerulean karma]

I am having trouble wrapping my head around the model

[lofty plaza]

Which one ?

[cerulean karma]

if I make it static, doesnt that just mean that getIn would be the same for all instances of Complex?

[lofty plaza]

That's not the point of static

It is the same for everything

Or rather

It's associated to the clasd

Not the object

Instead of calling the method on the object, you call it on the clasd

That's what static means

[cerulean karma]

Would that make a difference? Since the method uses it's own variables?

I have a hard time seeing the effect that static would have in terms of how the algorithm would work

[lofty plaza]

The difference is that one is called on the object, the other on the class

[cerulean karma]

What does it actually mean "called on", I can't envision it in my head

Right now, I don't see what difference it would make if it was being called from either the class or the object

[lofty plaza]

z.getIn()
Vs
Complex.getIn()

@cerulean karma

[cerulean karma]

Well yeah, but what difference would it make programm-wise

[lofty plaza]

Didn't I just showed you ?

[cerulean karma]

I just dont get it

[lofty plaza]

What do you not understand here ?

[cerulean karma]

what difference does it make who calls the method

[lofty plaza]

It's not how call it

It's on who you call it on

If you call it on z, then it means you must have an object to call it and this object is responsible for what happens in the method, which doesn't make any sense here

[cerulean karma]

is responsible?

How does that work?

Does the method use it's variables?

[lofty plaza]

A number is not supposed to ask user input that's what I mean

[cerulean karma]

Let me process everything for a sec

[cerulean karma]

I think I get it

shouldnt this be it then?

[lofty plaza]

You know you could have just made it static...
Anyway, don't name it scanner and make the scanner a field

[cerulean karma]

Like that?

or

[cerulean karma]

Are both the same?

[azure acorn]

btw its double not Double. hence its also yellow

[cerulean karma]

Oh, didnt notice that, thanks

[azure acorn]

no. the first creates a scanner when u do new ScanInput() and keeps it alive, reusing it. the second creates a fresh scanner each time u call getIn()

[cerulean karma]

So the first one is better then

[azure acorn]

yes

but ur probably supposed to make the scanner a static field

then its created once and reused all the time

instead of once per new ScanInput()

[cerulean karma]

My brain is fried

for whatever reason, even though I know what static is in theory, it bamboozles me in practise

[cerulean karma]

How do I do that

[polar oriole]

The keyword static controls ownership (not accessibility). A method or field that is static belongs to the class instead of an instance of a class. Suppose there is a simple class called Person:

class Person {
  String name;

  Person(String name) {
    this.name = name;
  }

  String getName() {
    return name;
  }
}

Now, you can create as many instances of this class as you want:

Person first = new Person("John");
Person second = new Person("Jane");

And each person has his own name, because it is non-static. So we can do

System.out.println(second.getName()); // prints Jane

In total, since there exist 2 instances of the Person class now, we also have 2 names and also 2 getName() methods. Each belonging to its corresponding instance of the class.

Now, if something is static, it belongs to the class and not to instances of it. While we just created 2 instances of Person, there exists exactly one class Person itself. So if we write:

class Person {
  static int amountOfEyes = 2;

  String name;

  Person(String name) {
    this.name = name;
  }

  String getName() {
    return name;
  }
}

Then amountOfEyes belongs to the Person class, not to the instances we created. As a result, there exist in total 2 names, 2 getName() methods but only one amountOfEyes variable.

As such, we also access this variable through the class, not through instances of it:

// Like this
System.out.println(Person.amountOfEyes);

So neither first nor second nor third have their own amountOfEyes. There is only one amountOfEyes and it belongs to the Person class itself.

To summarize, static things belong to the class, there is only one class no matter how many instances you create of it. Non-static things belong to instances of a class, each instance has its own set of non-static fields and methods.

Quinteger • used /tag id: static · Mar 24, 2023, 2:15 PM

[cerulean karma]

oh I see

Thank you!

Thank you all for your time, I am just getting the grasp of programming and it just doesnt come natural to me :3

/done

!done

[polar oriole]

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[cerulean karma]

/solved

[polar oriole]

Closed the thread.

[cerulean karma]

/inactive