Creating new objects

Thank you for the thorough explanation! It helps a lot! One thing though, how can getColor work when I haven't defined Color anywhere in this code? (We did in the previous challenges, but it's not visible now, so maybe it's there, but not visible?) I understand that 'get' always works, but how can getColor work? I mean, how can the computer know what it's supposed to 'get'? If you understand what I mean?

Also, I haven't defined newKart or similar in the visible code, so I get this error:

./Example.java:6: error: cannot find symbol

  System.out.printf(newKart.getColor());
                    ^

symbol: variable newKart location: class Example 1 error

I don't understand where and how to define it. Do I just make a string, or do I have to make a public class with it? Or..?

Hi Pauliina,

The getColor() method will work because the compiler you are working with knows what the GoKart class can do. So, once you've declared an instance of a GoKart, all its methods are available to that instance. So, inside of GoKart there's a method called (and it could be called anything, but it is good practice to name the getters and setters in this way) getColor that just returns the member variable called, probably, something like mColor.

public String getColor(){
  return mColor;
}

Something like that. So your instance of GoKart comes loaded with this functionality.

I'm not sure why you're getting the cannot find symbol error. The first part of this challenge was to define a new object of a GoKart. I called it newKart, did you call it something else?

You initial line of code should have something like:

GoKart newKart = new GoKart("RED");

Do you have that in there?

Steve.

No, I wrote that code in the previous challenges and now this is all the code that's there:

public class Example {

public static void main(String[] args) {
    System.out.println("We are going to create a GoKart");

The exercise says: "Now that you've created the GoKart class. Please create a new GoKart object using the GoKart class, or blueprint. As you know it takes a single parameter, color when being built."

So, do I need to re-write the old code? This is the code I have in the previous challenge:

public class GoKart { private String mColor = "red"; public String getColor() { return mColor; } }

I feel so lost. Everything was going great until this challenge came along, and now nothing makes sense anymore.

I think I understand! But why do we write GoKart newKart, and not String newKart or something similar? Is it because it's a new of -that- that we are making? But then again, we say new GoKart, so why do we need to write GoKart before too? Isn't that repeating? Wouldn't newKart = new GoKart ("blue"); work too?

Now that I got to the next challenge, I don't get that either.. It says "Challenge Task 2 of 2 Print out using System.out.printf the color of the new object, using the getColor method."

I feel like I didn't quite understand this whole thing, and it's not that much talked about in the video?

Thank you so much! It worked now! And I sorta get it. Just a couple of things though:

1. When do you use println and printf? What's the difference?
2. How do you know when to put in parameters in a method? Like the getColor(), even though the parameters are empty. Do you always put () in methods?
3. So, have I gotten this right? Getters, like getColor, and helpers, like isEmpty, are "built in", so they always work on classes? You don't have to define them or similar? Or..?

Also, I feel like I'm not understanding as much as I should. I'm doing this course, but that's it for now. I want to get in to a programming program at uni next autumn, but in this pace I'll never be good enough. How can I get better and understand more? I feel like everything I read just go in and out immediately. Nothing gets stuck unless I use it in an actual code, but I'm not good enough to code anything myself. My brain is kinda off lately due to stress, so that's why nothing makes sense anymore.. Very irritating.

OK - you're making progress - that's cool.

1. printf and println do similar things - I think one is called on the console object and the other isn't. I really wouldn't worry about the differences - they're academic and probably easily discovered with a quick Google.
2. All methods have brackets, yes. If the method taes no parameters, the brackets are empty, if the method does take a parameter, it'll throw an exception when you leave it out. ;-) Nah, seriously, the method signature will show you that it takes a parameter - we can use the getter & setter question, next, as an example.
3. Getters and setters aren't built-in, no. You write them. The IDE (like Android Studio) will help you create them, but you do need to define them, unfortunately. Getters are pretty easy - they just return the private member variable, like getColor() returned mColor. Setters can be a little more complicated but the principle is identical - you pass a value in an it sets the appropriate value in the member variable. Let's use setColor() as an example - this shows you what a parameter looks like too:

public void setColor(String color){
  mColor = color;
}

The member variable mColor has private access so only things inside the class can amend it. That's why we use getters and setters - it protects the member variable from changes as changes can only be made by the G & S. This method is a setter. It has public access, returns nothing (void). It's called setColor by convention. It takes one parameter which is a String and inside the method, that string can be used with the variable named color. That variable can be named anything and it doesn't matter what it is called when it is passed into the method - it just need to be of type String.

So you could ave some code asking the user for their favourite colour so you can create a GoKart for them.

//create a Kart for the user - unsure of colour
GoKart steveKart = new GoKart("DUNNO");
// ask for the colour
String favouriteColor = console.readLine("What is your favourite colour?: ");
// users answers "RED"
// call the setter
steveKart.setColor(favouriteColor);

That parameter, favouriteColor goes into the setter method. Inside the setter method, the value contained in favouriteColor is accessed by using the local name, color and the privte member variable, mColor, for the instance steveKart is set to "RED".

public void setColor(String color){  // String color = favouriteColor
  mColor = color; // sets mColor to color which is the same as favouriteColor
}

I'm good at making stuff over-complicated - I do hope that made some sense!!

Steve.

No, but I think I get it. Thanks! Do you have any tips on how to get better at programming? Is it just practice, practice, practice? Should I repeat the courses I've already done in Java? Should I read books? Read code? Etc.

I think that you're over estimating how much you should remember and under estimating how much you do remember. Learning a new language is really hard at first but it gets less challenging the more you do it. Everyone learns differently; some like to learn a load of languages in parallel as the common themes reinforce each of them - I get that. Others prefer to stick to one language - I get that too.

For me, it is all about repetition. Keep going over the concepts and trying to articulate them into English, rather than just code. I find that being in these forums really helps with that. Have a read at other people's posts in the same course you're in - see what responses say. Those responses will be articulating what I've written in this thread but in a different way. That way may suit you better - hearing the same message said in different contexts is a good way of getting it to sink in.

Keep going with the course on here. The Java stuff is quite heavy - Craig pushes you a lot in his courses which is great! Then try something on the Android course - that's all in Java too - that's a little less techy in approach but still a great set of courses taught by Ben. Just keep plugging away and asking in the COmmunity pages when you're having trouble. Also, look at other people's posts, like I suggested. You'll be answering posts in no time! But just being among the questions helps your brain iron out the bits you're not quite getting.

You'll make that course at Uni - just keep at it and try different elements of Java.

I hope that helps.

Steve.

Thank you again, Steve. I really appreciate the time you've taken to help me out. I feel like I'm finally back on track, and now things are going along much smoother! I will keep practicing and repeating things I don't fully grasp, I'll read a lot in the forum and I'm now taking notes on everything so that I can go back if I get lost and see how I described things. Things are making much more sense now. Thank you again! I think I needed a little kick in the butt.

Cool - I'm glad you feel a little better about it. Keep up the good work!

And if you get stuck, you can always @ mention me in here and I'll come and see if I can help.

Steve.

I agree that the fundamentals of programming are common across pretty much all languages. Individuals may 'get along' better with some syntax over others, as you've found with JS. But coming across new concepts for the first time in whichever language can cause initial confusion often caused by a lack of confidence or familiarity.

Repetition remains a good way of embedding new skills; hoping to remember concepts after just one pass is a challenge. Revisiting the same, or similar, concept in a different context such as a different language, is a great way to solidify the foundation of that knowledge.

Steve.

I have no prior programming experience. I've tried JavaScript, just for a couple of hours, before I started with Java. But, like Steve says, it just confused me. I mixed up all the different words etc. Plus, I wont need JavaScript for anything as I truly hate making webpages and web-based things. Java makes more sense to me. So, I'm just gonna keep practice Java for now!

Hi Christiaan,

The concepts can seem challenging at first. But, as you say, if you work with them they will become familiar and you'll grow your understanding. These concepts are cross-language so they are transferable in other language than Java. The way the code is written may be slightly different but the concept of classes and instance/objects are the same.

Keep on working your way through it and ask questions in the Community pages if you get stuck.Trying to articulate a question forces you to think about what you know and where your knowledge gap is. That really helps solidify your thoughts.

Enjoy your courses. :-)

Steve.