Java 101 — Variables and Parameters

Variables are useful to store information that later we can use.In order to use a variable first we must declare them.

We start with the type of variable followed by the variable name and it's value.

public class Variable
    public static void main (String [] args)
      byte variable1;
      // Can store -128 to 128
      short variable2;
      // Can store -32768 to 32768
      int variable3;
      // Can store 2147483684 to 2147483684
      long variable4;
      //Can store really huge numbers
      float variable5;
      // Can store large decimal range
      double variable6;
      // Can store huge decimal range

Area of a Rectangle

The following class calculates the area of a rectangle using variables.

public class Area
    public static void main (String [] args)
      int length = 5;
      int width = 10;
      int area = length * width;
      System.out.println("The area of the rectangle is " + area );


If you want to store a double in an integer the JVM will throw an expection because a double wont fit in an integer. The solution is casting.

int myVar = (int) myDouble;

When casting from one type to another, always use the type that you are converting to as the cast.