Thread: Details about 'CopyTo' of Arrays in Java

Hello Fendaril,

Welcome to the Java Programming Forums

copyFrom and copyTo are actually just variable names. These are unique names you declare to your variables in order to identify them later on.

In this case you have 2 char variables called copyFrom and CopyTo but you could easily have something like

String myName = "John";

There you have created a String variable called myName containing the String 'John'

The code:

char[] copyTo = new char[7];

Declares an char variable array which will hold 7 characters.

The System.arraycopy basically prints out the array data from position 2 through to 7.

These char array variables could be called anything you want. They are not actual java code. I hope you understand what I mean..

Hey Fendaril,

Its my pleasure.

I know the feeling.. Its quite daunting when first starting to write Java code. It seems like there is soooo much to learn.

What I would suggest is that you start your own code library. Create a folder somewhere on your computer and create .txt files containing different code. For example, I would have one containing code for reading files, reading input from the console, an array example etc. Name each file approperatly and then when you are writing new code you can check your library as a reference.

The trick really is to practice. The more real world applications you can write the better. It takes time but eventually things start to click into place and it becomes alot easier.

You will never stop learning. Ive been writing Java code for quite a few years now but im still learning every time I code.

There is an official Java exam called the SCJP "Sun Certified Java Programmer" Take a look at some of the ebooks we have on this site. Because they are designed to help you pass the exam, they cover every aspect of Java and will help you to understand areas you are unsure about.

http://www.javaprogrammingforums.com...-new-post.html

Remember, google is your friend. You will find nearly all your answers there and posting in forums like this one will also help you on your way

That e-book on JAVA really cleared up Arrays for me. To tell you the truth I thought that all arrays had to be named "anArrayOfString;". I had no clue that I could name them what I want and initialize them on the same line. Goes to show how easy it is to misread JAVA sun's tutorials.

I found this cool datatype called "Object" that can hold anything!!!!!

I can even create arrays with it!!!

What is the catch. Will is affect the speed of my program by alot?

I'm glad that ebook has helped you. There is lots of useful information in there!

Check this link out and read about what an Object is.

What Is an Object? (The Java™ Tutorials > Learning the Java Language > Object-Oriented Programming Concepts)

This is the very fundamentals of object oriented programming.

Welcome to the world of Java

What is the catch. Will is affect the speed of my program by alot?

Java is powerful. You would need some really heavy code to slow down your program by a noticable amount. You do not need to worry too much.

Originally Posted by Fendaril

I meant this:

object test= 1234;(Is this more efficient then declaring an int?)

You must use the correct variable for whatever type of data you are trying to hold. String, int, char, byte, double, etc.

This makes it easy to identify exactly what you are doing and makes for good programming.

Originally Posted by Fendaril

Thanks. Now one more question.SOrry for all of them. What are good places to do excercises?

Its no problem Fendaril... Thats what we are here for

How do you mean by exercises? Are you looking for inspiration in what to code or are you looking for step by step instructions you can follow?

If your looking for a few simple ideas then im sure I can chuck a few your way.

Its good to write code that will help you learn different aspects of Java.

Do you feel you understand arrays enough now?

How are you with the different loops? for loop, while loop etc?

You could try to incorporate the use of an array and a for loop into one program.

Create an array of Names and use a for loop to print them all to the console.

ah yeah I can see why you would think this code is more complicated when it actually isnt.

This is still a String array and for loop printing its content.

Array values can be stored like this:

String[] names={"bob","jill","frank","stewart","charlie"};

This is the same as:

String[] name = new String[5]
 
name[0] = "bob";
name[1] = "jill";
name[2] = "frank";
name[3] = "stewart";
name[4] = "charlie";

I think this concept first came into Java in version 4/5. They both work the same, its just down to personal preference to which one you use.

for(String item: names){
            System.out.println("This name in the array is " + item);
        }

The basic for loop was extended in Java 5 to make iteration over arrays and other collections more convenient. This newer for statement is called the enhanced for or for-each loop. Again its down to personal preference which one you use but keeping with the times makes it more readable.

so the reason I thought the candidate program was hard was because of the fact that he used a different method of array?

would it be more beneficial to create a standard for loop and have it iterate over the length while I print the arrays?

Yeah the reason it looked hard was because they used a different method of array.

As far as im aware, there is no difference in performance between the for and for-each loop. But if you want to print the content of an array I would get used to learning the for-each loop as its more convenient and no doubt you will encounter it alot in the future.

Originally Posted by Fendaril

Yes the easy part is over.

Classes and objects seem to go through one ear and out the other...

It will take time to sink in. Classes and Objects are the base of Object Oriented Programming.

Spend some time to read through the Sun Java tutorials about Classes and Objects. Even if you have read it 5 times before, read it again.

Lesson: Classes and Objects (The Java™ Tutorials > Learning the Java Language)

You need to keep reading even if you don't understand. Each time it will gradually sink in more and more. Try to write code that will help you to understand. For example, try to pass a variable between 2 different classes..

I remember it took me a while to get my head around OOP too. The key really is just to keep writing code.

I havent done anything related to java in 2 days. I got so stressed out and just played games. I feel so incomplete so I am going to do something worthwhile.


Ok so I think I came upon a good project to start out with. I found out how to pass variables through different methods.

What if I passed variables through methods like 'addition(i,j)' while taking input from the user. It does require me to jump a head a little bit but a calculator is something that is very easy to make. I could use the beautiful if-else ladder. The process I have to take to make it is a bit harder then in c++. Not comparing or anything.