Learning Java/Objects and Classes: Difference between revisions
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=Classes=
Classes are the core of Java. Everything is done within classes. You already know how to create a class:
<pre>
{
}
▲pblic class AME
</pre>
You can also have multiple classes in a single file:
<pre>
public class NAME
{}
class otherClass
{}
</pre>
otherClass can be run by <code>java otherClass</code> just like normal. You can use these classes in objects...
==Fields==
Fields are variables declared in the class itself - not in any method. For example, the following is a field:
<pre>
class SomeClass
{
int field;//This was not declared inside any method
}
</pre>
Fields have many purposes, as they are global variables. They can be accessed from outside the class in objects (see Objects).
==Methods==
You have used one method in each of your programs - main(String[] args). Methods basically contain statements that help finish a purpose. You cannot put all types of statements outside of a method. Methods have a 'parameter'. That is the area between ( and ). Also, they have a return type. For example, a return type of int means that somewhere in the method it returns an Integer (you will understand this as you create and see methods). Methods are also like blocks - they have a { and }. Everything within that is executed when you "call" the method. Lets examine main again:
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public class Ship
{
public int speed;//Must be public - its accessed from outside the class
public Ship()▼
{
speed=0;//You are going at speed of 0 at the dock
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