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Variables

The Aims​

This lab will introduce you to using the primitive variable types, the basic operators, and the concept of casting.

Remember – Java is case sensitive!

Create a new Java Project​

  1. Using your IDE, create a new Java project.

  2. The IDE might create a new class for you - if it doesn't create a class called "Main.java", containing the following content:

    class Main {
        public static void main(String[] args) {
            
        }
    }

  3. If the IDE created this class for you, change the content in this class so that it matches the above.

Declaring and initialising variables​

  1. Within the main method, you will declare some variables to represent the car you drive, or if you do not have a car – a car you would like to drive! Firstly declare two variables of type String called make and model, then declare a variable of type double to be the engineSize, and declare a variable of type byte to be the gear your car is in.

  2. Now initialise those variables with appropriate values. Put in some code so that the program will print out the values of these variables, things like;

The make is x
The gear is y
The engine size is z

You can join String and other variables together by using the concatenator (+).

  1. Fix any errors and run the application.

Click here to see the sample solution

public class Main
{
       public static void main(String[] args)
       {
              String make = "BMW";
              String model = "530D";
              double engineSize = 3.0;
              byte gear = 2;

              System.out.println("The make is " + make);
              System.out.println("The model is " + model);
              System.out.println("The engine size is " + engineSize);
         }
}

Casting​

  1. Now declare a variable of type short to be the speed. This variable will be the result of the gear multiplied by 20 (not scientific but it will do for now!).

  2. Put in a line of code to set the speed to equal the gear multiplied by 20. You will need to cast to get it to compile (why?).

  3. Print out the speed to the console, and run your program to check that it works correctly.

Click here to see the sample solution

public class Main
{
       public static void main(String[] args)
       {
              String make = "BMW";
              String model = "530D";
              double engineSize = 3.0;
              byte gear = 2;
              short speed = (short)gear * 20;

              System.out.println("The make is " + make);
              System.out.println("The model is " + model);
              System.out.println("The engine size is " + engineSize);
              System.out.println("The speed is " + speed);
         }
}

Optional Extras​

  1. Modify your code so that you have a number of other variables of different types. Build in some simple arithmetic, printing out your results to the console. You could place in an int for example to be the revs, which could be based on the speed variable multiplied by the gear!