Java:Discount

the whole year inn

punk_one82 wrote: »

Code looks okay. You're along the right lines, but there are a few mistakes. Try compiling that class and see what the compiler complains about. Specifically think about the logic and types in your set methods, as well as what's going on in your printProduct method.

As an aside - I'd try work on your code formatting. It's pretty hard to read at the minute.

I fixed the println,the closed it off and add a semi colon.Theres no errors in eclipse and when I run it terminates.

I also have one problem with this question.
I understand that its tondo with inheritance mammal extends dog but stuck on it.

the whole year inn

This is the question.

Buford T Justice

the whole year inn wrote: »

I fixed the println,the closed it off and add a semi colon.Theres no errors in eclipse and when I run it terminates.

I also have one problem with this question.
I understand that its tondo with inheritance mammal extends dog but stuck on it.

What are you asking specifically?

the whole year inn

Buford T Justice wrote: »

What are you asking specifically?

Any examples i find online just show a snippet of the code and I dont know how to answer the question.

Buford T Justice

the whole year inn wrote: »

Any examples i find online just show a snippet of the code and I dont know how to answer the question.

So you want us to do your homework for you, or is there an aspect of the question you would like help with?

Have you read something like this?

bpmurray

One other thing - when you post your code, surround it with a [ CODE] and a [ /CODE] (there shouldn't be spaces after the "[") to make it legible. What are you using to develop? Do you have Eclipse or something similar? That will format your code for you - formatting, meaningful variable names and comments are essential to make your code readable.

Edit: your formatting seems to indicate that you're afraid of whitespace. When talking to 8-year-olds at CoderDojo, this is something I have to repeat quite often but they get it fairly quickly. I suggest you hit <ENTER> more often and include plenty of spaces. For example you have:
public Product (int i,String s,float p)
{id=i;
name=s;
price=p;
}

While the normal formatting (using [ CODE]) is:

public Product (int i, String s, float p)
{
    id    = i;
    name  = s;
    price = p;
}

Also, in this case, I'd emphasise that the variables are class variables by using this:

public Product (int i, String s, float p)
{
    this.id    = i;
    this.name  = s;
    this.price = p;
}

punk_one82

the whole year inn wrote: »

I fixed the println,the closed it off and add a semi colon.Theres no errors in eclipse and when I run it terminates.

I also have one problem with this question.
I understand that its tondo with inheritance mammal extends dog but stuck on it.

There may be no errors after you fixed your print method, but look at your set methods. What are they doing? Are the parameters you're passing in to those methods of the right type? Are they setting the values on any class variables?

Your set methods are currently doing nothing at all, hence there being no errors. Make your set methods set something and then figure out what's wrong with the parameters.

Edit: On the inheritance question - "mammal extends dog". Think about it logically. Does a mammal actually extend dog? A dog is a type of mammal -> A labrador is a type of dog. The arrows in the question give the hierarchy. Mammal -> Dog -> Labrador.

the whole year inn

punk_one82 wrote: »

There may be no errors after you fixed your print method, but look at your set methods. What are they doing? Are the parameters you're passing in to those methods of the right type? Are they setting the values on any class variables?

Your set methods are currently doing nothing at all, hence there being no errors. Make your set methods set something and then figure out what's wrong with the parameters.

Edit: On the inheritance question - "mammal extends dog". Think about it logically. Does a mammal actually extend dog? A dog is a type of mammal -> A labrador is a type of dog. The arrows in the question give the hierarchy. Mammal -> Dog -> Labrador.

package Product;

public class Product {
// Private variables
private int id;
private float price;
private String name;

public Product ( int i,String s,float p)
{this.id=i;
this.name=s;
this.price=p;
}
public int getId()
{return id;
}
public void setId (int newId) {
	{
id=newId;}
}

public String getName()
{return name;
}
public void setName (String newName) {
name=newName;
}


public float getPrice()
{return price;
}
public void setprice (Float newPrice) {

price=newPrice;
}


// Display the rectangle information
public void printProduct() {
System.out.println("Priceprice");
System.out.println("Namename");
System.out.println("Idid");
}
		}
]

I had another stab at it,how does it look now,if im honest I think its right.Im getting afew grinds tomorrow so hopefully that helps.

the whole year inn

Buford T Justice wrote: »

So you want us to do your homework for you, or is there an aspect of the question you would like help with?

Have you read something like this?

Thanks I learning this now.

croo

the whole year inn wrote: »

how does it look now,if im honest I think its right.

Do you get the results you expect when you run it?
I don't image so!

To re-iterate a couple of points others have already said.

Anesthetize wrote: »

never use single letters for variable or parameter names. Use something descriptive. Other people need to be able to understand what the code is doing just by reading the code.

And you wrote...

public Product ( int i,String s,float p) {
     this.id=i;
     this.name=s;
     this.price=p;
}

But, at least you did follow bpmurray's advice of using this

bpmurray wrote: »

in this case, I'd emphasise that the variables are class variables by using this:

but only for the one method he provided and example for but not in any other method.

It will still compile & run; it's just not considered best practise. On a small exercise like this it will make little difference but it's a bad habit to get into so why not just do it right to start with and not develop any of those bad habits!

So standard practice would be to use descriptive variable names and when setting those use the this keyword.

public Product ( int id, String name, float price) {
     this.id = id;
     this.name = name;
     this.price = price;
}

And that practise should be applied applied to all methods so, taking just one, as an example.

public void setId (int id) {
     this.id = id;
}

Would be following best practise.

the whole year inn

croo wrote: »

Do you get the results you expect when you run it?
I don't image so!

To re-iterate a couple of points others have already said.

And you wrote...

public Product ( int i,String s,float p) {
     this.id=i;
     this.name=s;
     this.price=p;
}

But, at least you did follow bpmurray's advice of using this
but only for the one method he provided and example for but not in any other method.

It will still compile & run; it's just not considered best practise. On a small exercise like this it will make little difference but it's a bad habit to get into so why not just do it right to start with and not develop any of those bad habits!

So standard practice would be to use descriptive variable names and when setting those use the this keyword.

public Product ( int id, String name, float price) {
     this.id = id;
     this.name = name;
     this.price = price;
}

And that practise should be applied applied to all methods so, taking just one, as an example.

public void setId (int id) {
     this.id = id;
}

Would be following best practise.

Well the questions stats to use i,s etc,I am just following the what the question is looking for.
I will add this to the other methods.
For the code to work whats wrong with it?

croo

the whole year inn wrote: »

Well the questions stats to use i,s etc,

Fair enough.

the whole year inn wrote: »

For the code to work whats wrong with it?

Well does it compile?
Does it provide you the result you were expecting?

the whole year inn

croo wrote: »

Fair enough.

Well does it compile?
Does it provide you the result you were expecting?

Well for the question that was asked from the exam question,I think it does.I will get the question again and see what you think.

Thats the question.
https://us.v-cdn.net/6034073/uploads/attachments/10189/393253.jpg

the whole year inn

Buford T Justice wrote: »

So you want us to do your homework for you, or is there an aspect of the question you would like help with?

Have you read something like this?

class mammal {
	String gender;
	
	public mammal(string g){
		gender = g;
	}
}

==========================================================

class dog extends mammal{

	String breed;
	
	public dog(string g, string b){
		super(g);
		breed = b;
	}
	
}

==============================================================
class labrador extends dog {
	
	String eyecolor;
	
	public labrador(String g, String b, String ec){
		super.(g,b)
		eyecolor = ec;
	}
	
}

Thats the answer I have for that question

punk_one82

the whole year inn wrote: »

class mammal {
	String gender;
	
	public mammal(string g){
		gender = g;
	}
}

==========================================================

class dog extends mammal{

	String breed;
	
	public dog(string g, string b){
		super(g);
		breed = b;
	}
	
}

==============================================================
class labrador extends dog {
	
	String eyecolor;
	
	public labrador(String g, String b, String ec){
		super.(g,b)
		eyecolor = ec;
	}
	
}

Thats the answer I have for that question

You're getting there. Still don't think it will compile, but if you try compile it the problems should be glaringly obvious.

You coding style has improved drastically, but it's still best practice to use the "this" keywork when referencing class level variables eg. this.eyecolour = ec;

I'd probably use an abstract base class also, but not sure that's required for the question

pillphil

the whole year inn wrote: »

class mammal {
	String gender;
	
	public mammal(string g){ // line 1
		gender = g;
	}
}

==========================================================

class dog extends mammal{

	String breed;
	
	public dog(string g, string b){ // line 2
		super(g);
		breed = b;
	}
	
}

==============================================================
class labrador extends dog {
	
	String eyecolor;
	
	public labrador(String g, String b, String ec){
		[B]super.(g,b)[/B]//line 3
		eyecolor = ec;
	}
	
}

Thats the answer I have for that question

Program fails to compile due to errors in lines 1, 2 and 3?

Also, should classes begin with a capital letter?

Are you actually trying to run the code? That will show you where you are going wrong pretty quickly.

punk_one82

As above, try compile the code when you're writing it. If you're practicing for a handwritten test write it in notepad and try compile it when you think you're done. You'll start spotting your common errors and can get the correct way of doing it in your head.

the whole year inn

punk_one82 wrote: »

As above, try compile the code when you're writing it. If you're practicing for a handwritten test write it in notepad and try compile it when you think you're done. You'll start spotting your common errors and can get the correct way of doing it in your head.

Thanks everyone.I am getting a little bit more confident.In reguards to the to the product class I have done above,can someone tell me whats exactly wrong with it.
I known I have to add this. In parts but other than that what else is wrong?I thought it was right.
I add it to eclipse and check but in the product class I dont get an error so not sure why some posters said it was wrong or why its wrong.Can anyone help with that?

punk_one82

class [B]M[/B]ammal {
	String gender;
	
	public [B]M[/B]ammal([B]S[/B]tring g){
		[B]this.[/B]gender = g;
	}
}

class [B]D[/B]og extends [B]M[/B]ammal{

	String breed;
	
	public [B]D[/B]og([B]S[/B]tring g, [B]S[/B]tring b){
		super(g);
		[B]this.[/B]breed = b;
	}
	
}

class [B]L[/B]abrador extends [B]D[/B]og {
	
	String eyecolor;
	
	public [B]L[/B]abrador(String g, String b, String ec){
		[B]super(g,b);[/B]
		[B]this.[/B]eyecolor = ec;
	}
	
}

Compare this to your code.

the whole year inn

punk_one82 wrote: »

class [B]M[/B]ammal {
	String gender;
	
	public [B]M[/B]ammal([B]S[/B]tring g){
		[B]this.[/B]gender = g;
	}
}

class [B]D[/B]og extends [B]M[/B]ammal{

	String breed;
	
	public [B]D[/B]og([B]S[/B]tring g, [B]S[/B]tring b){
		super(g);
		[B]this.[/B]breed = b;
	}
	
}

class [B]L[/B]abrador extends [B]D[/B]og {
	
	String eyecolor;
	
	public [B]L[/B]abrador(String g, String b, String ec){
		[B]super(g,b);[/B]
		[B]this.[/B]eyecolor = ec;
	}
	
}

Compare this to your code.

Ok I will thanks

pillphil

In relation to the product class, I don't want to just give you the answer, but if I create a new product object

Product p = new Product(123, "Milk", 1.20f);

and call the printProduct method

p.printProduct();

I expect to see this as an output (as per the question)

ID: 123
Name: Milk
Price: €1.20

However, what actually is output is

Priceprice
Namename
Idid

I don't mean to be an arse, but if you have to ask why it's wrong, it means you either didn't compile and run the code or you don't understand the question.

the whole year inn

pillphil wrote: »

In relation to the product class, I don't want to just give you the answer, but if I create a new product object

Product p = new Product(123, "Milk", 1.20f);

and call the printProduct method

p.printProduct();

I expect to see this as an output (as per the question)

ID: 123
Name: Milk
Price: €1.20

However, what actually is output is

Priceprice
Namename
Idid

I don't mean to be an arse, but if you have to ask why it's wrong, it means you either didn't compile and run the code or you don't understand the question.

Your not an arse,helping alot actuially!
I emailed the lecture about this and asked do I have to do a test class to print out the info,as I would understand how to do that?He never got back to me.
Or can I do it all from this and not create a new test class?

Buford T Justice

the whole year inn wrote: »

Your not an arse,helping alot actuially!
I emailed the lecture about this and asked do I have to do a test class to print out the info,as I would understand how to do that?He never got back to me.
Or can I do it all from this and not create a new test class?

Just create another class with a main method that creates the object and printproduct method

the whole year inn

Buford T Justice wrote: »

Just create another class with a main method that creates the object and printproduct method

Thanks,thats what I was getting at,I thought the question said to create a class which I thought was one,in other questions it asks for the other class to be created so that where I misunderstood.
thanks !

croo

the whole year inn wrote: »

I emailed the lecture about this and asked do I have to do a test class to print out the info

pillphil didn't mean that you didn't have code to test print the product info but that the method you have

// Display the rectangle information
public void printProduct() {
System.out.println("Priceprice");
System.out.println("Namename");
System.out.println("Idid");
}

does not actually print the info!

PS. even if the method was printing the product info the layout you have does not match that requested. A minor issue perhaps while learning to code but for an exam question it's these minor issues that might mean the difference between a correct answer and a perfect answer!

the whole year inn

croo wrote: »

pillphil didn't mean that you didn't have code to test print the product info but that the method you have

// Display the rectangle information
public void printProduct() {
System.out.println("Priceprice");
System.out.println("Namename");
System.out.println("Idid");
}

does not actually print the info!

PS. even if the method was printing the product info the layout you have does not match that requested. A minor issue perhaps while learning to code but for an exam question it's these minor issues that might mean the difference between a correct answer and a perfect answer!

Ok I will try and get this right,it has came up a few times in the exam papers so would like to get it right.

pillphil

croo wrote: »

pillphil didn't mean that you didn't have code to test print the product info but that the method you have

// Display the rectangle information
public void printProduct() {
System.out.println("Priceprice");
System.out.println("Namename");
System.out.println("Idid");
}

does not actually print the info!

PS. even if the method was printing the product info the layout you have does not match that requested. A minor issue perhaps while learning to code but for an exam question it's these minor issues that might mean the difference between a correct answer and a perfect answer!

Annoyingly, it gives two different sample layouts.

@the whole year in
The exam question doesn't require you to have a test class to execute the code you've written, however you should write one if only to see what your code is actually doing.

the whole year inn

Had the exam today,thought it was hard but I passed I think(hopefully) thanks everyone who helped here.

punk_one82

the whole year inn wrote: »

Had the exam today,thought it was hard but I passed I think(hopefully) thanks everyone who helped here.

Congratulations. Keep plugging away. Some things in programming seem difficult or bizarre at first, but then they click and become second nature.