# Variables & Types¶

In this lab you will parse a number (hours) from the command-line arguments and calculate the number of seconds in those hours. For example:

``````\$ java HoursToSeconds 2
Number of seconds in 2 hour(s) is 7200
``````

Remember: Don't copy-and-paste any code from here, get your fingers used to typing the code.

## Step 1: Create a New Class With Entry Point¶

Create a new file, `HoursToSeconds.java`, and inside of that file, define a class with the same name, `HoursToSeconds`, e.g.:

``````public class HoursToSeconds {
}
``````

Create a new entry point method inside the class, e.g.:

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

## Step 2: Calculate "Seconds Per Hour" Using an `int` Variable¶

Inside of the `main` method (the entry point), write code that creates an `int` variable named `hours` and assign 1 to it.

``````int hours = 1;
``````

Compute the number of seconds for those hours:

``````int hoursInSeconds = hours * // fill in the rest of this computation yourself!
``````

## Step 3: Print the Result¶

Using `System.out.println()`, print out the text "Number of seconds in 1 hour(s) is 3600", but replace the `1` with the value from the `hours` variable, and the `3600` with the calculated number of seconds.

Remember to Use String Concatenation

For example: to print "I have worked here for 2 years and 3 months", you might write:

``````int years = 2;
int months = 3;
System.out.println("I have worked here for " + years + " years and " + months + " months");
``````

## Step 4: Compile and Run¶

Save the file `HoursToSeconds.java`, compile it, and then run it, e.g.:

``````\$ java HoursToSeconds
Number of seconds in 1 hour(s) is 3600
``````

## Step 5: Parse Hours from the Command Line¶

Now let's get the number of hours from the command line arguments, instead of "hard-coding" it.

Replace the `int hours = 1;` with `int hours =` and use the `Integer.parseInt()` method to convert the first command-line argument from a `String` to an `int`, storing it in the `hours` variable.

Everything else should remain the same, so do the same routine:

• Compile the Java file
• Run it and pass a number as a parameter:
``````\$ java HoursToSeconds 2
Number of seconds in 2 hour(s) is 7200
``````

## Experiment¶

Things to try:

• What if you don't pass anything on the command-line?
• What if the String isn't a valid number?
• What if the String isn't an integer (i.e., decimal)?
• What else might you try? Once you've completed the above steps, check in with the instructor to review your code.