How we Use a Car object in a different class ?

class Car {

String licensePlate; // e.g. "New York 543 A23"
double speed; // in kilometers per hour
double maxSpeed; // in kilometers per hour

}
The further program creates a new car, sets its fields, and prints the result:
class CarTest {

public static void main(String args[]) {
Car c = new Car();
c.licensePlate = "New York A45 636";
c.speed = 70.0;
c.maxSpeed = 123.45;
System.out.println(c.licensePlate + " is moving at " + c.speed +
" kilometers per hour.");
}
}
This program needs not just the CarTest class other than also the Car class. To make them work together put the Car class in a file known as Car.java. Put the CarTest class in a file known as CarTest.java. Put both these files in the similar directory. Then compile both files in the common way. At last run CarTest. For example,
% javac Car.java
% javac CarTest.java
% java CarTest

New York A45 636 is moving at 70.0 kilometers per hour.
Remember that Car does not have a main() techniques so you cannot run it. It can exist only when called through other programs in which do have main() methods.

Several of the applications you write from now on will use multiple classes. It is customary in Java to put every class in its own file. Next week, you'll learn how to use packages to organize your commonly used classes in different directories. For now remain all your .java source code and .class byte code files in one directory.