How do I substitute any variable for a hardcoded variable

**Weazel Boy** · 07-07-2010, 05:09 AM

Hello Everyone,

I'm trying to get my program to work with any variable and I want to avoid hardcoding. Are there any simple fixes for this?

Java Code:

public class Prog4
{
  public static void main(String[] args)
  {
    double speed = 40;
    double stoppingDistance;
    System.out.println("Enter speed: " + speed);
    stoppingDistance = (speed * (2.25 + speed / 21));
    System.out.println("Stopping distance: " + stoppingDistance);


    if (stoppingDistance < 178.5)
    {
    System.out.println ("No problem");
    }//end if

    else if (stoppingDistance == 178.5)
    {
    System.out.println("Minor Wreck");
    }//end else if

    else
    {
    System.out.println("Major Wreck!");
    }//end else
  }//end main
}//end class Prog4

**al_Marshy_1981** · 07-07-2010, 05:16 AM

What variable do you wish to substitute? It does not really matter there are numerous ways for you to set variables, you can set variable from the command prompt if you wish

**doWhile** · 07-07-2010, 05:19 AM

If you wish to send input into the program, look at Scanner (Java 2 Platform SE 5.0), or send command line arguments sent via the args variable.

**Eranga** · 07-07-2010, 05:38 AM

I think that OP wants to change the speed variable. Use scanner class to get the user inputs from the command prompt.

**Weazel Boy** · 07-07-2010, 05:38 AM

Thanks al Marshy - I would like to substitute 40 (speed) with any non-hardcoded variable.

**al_Marshy_1981** · 07-07-2010, 05:48 AM

it is temporarlily gone out of my head but its a quick experiment to find out which one, when you run a program from command prompt you can provide values.. reference---> Command-Line Arguments (The Java™ Tutorials > Essential Classes > The Platform Environment)

all you have to do is set that speed variable to args[0], im pretty sure the first argument is the variable. Just remember arguments come in as Strings so you will have to parse them to a double, here....

e.g.

Java Code:

double speed=Double.parseDouble(args[0]);

where args[0] is the value passed at the command prompt.

Other than this like Eranga says use Scanner class Scanning (The Java™ Tutorials > Essential Classes > Basic I/O) (or DoWhiles link) to get values from user input and assign them to the speed variable..

**Eranga** · 07-07-2010, 05:50 AM

And also you've think about how to validate user inputs, like string literals rather digits.

**Weazel Boy** · 07-07-2010, 06:15 AM

Thanks Eranga does this look right?

import java.util.Scanner;

Java Code:

public class Prog4
{
  public static void main(String[] args)
  {
    Scanner keyboard = new Scanner(System.in);
    String speed = "";
    keyboard.nextLine();

    double speed;
    double stoppingDistance;
    System.out.println("Enter speed: " + speed);
    stoppingDistance = (speed * (2.25 + speed / 21));
    System.out.println("stoppingDistance: " + stoppingDistance);


    if (stoppingDistance < 178.5)
    {
    System.out.println ("No problem");
    }//end if

    else if (stoppingDistance == 178.5)
    {
    System.out.println("Minor Wreck");
    }//end else if

    else
    {
    System.out.println("Major Wreck!");
    }//end else
  }//end main
}//end class Prog4

**al_Marshy_1981** · 07-07-2010, 06:30 AM

I can't see where speed is read in from user input and then used.

Java Code:

Scanner keyboard = new Scanner(System.in);
String speed = "";
keyboard.nextLine();

Also you have a String called speed and a double called speed.

try

Java Code:

Scanner keyboard = new Scanner(System.in);
System.out.print("Enter the value for speed: ");
String input=keyboard.nextLine();
double speed=Double.parseDouble(input);

Now you have a value for speed as a double.

**Eranga** · 07-07-2010, 06:55 AM

Originally Posted by al_Marshy_1981

Java Code:

Scanner keyboard = new Scanner(System.in);
     // Create a new scanner object

System.out.print("Enter the value for speed: ");
     // Display a message to the user

String input=keyboard.nextLine();
     // Read the next line (if the use enter a text?)

double speed=Double.parseDouble(input);
     // Convert the string literal to a double value

Now you have a value for speed as a double.

I agreed with you, OP hasn't assign any user inputs to the speed variable.

**Weazel Boy** · 07-07-2010, 06:57 AM

Thanks for all the help everyone!! I was able to use the scanner tool to help solve it.

import java.util.Scanner;

public class Prog4
{
public static void main(String[] args)
{
Scanner xyz = new Scanner(System.in);
double speed;
speed = xyz.nextDouble();

double stoppingDistance;
System.out.println("Enter speed: " + speed);
stoppingDistance = (speed * (2.25 + speed / 21));
System.out.println("stoppingDistance: " + stoppingDistance);

if (stoppingDistance < 178.5)
{
System.out.println ("No problem");
}//end if

else if (stoppingDistance == 178.5)
{
System.out.println("Minor Wreck");
}//end else if

else
{
System.out.println("Major Wreck!");
}//end else
}//end main
}//end class Prog4

**Eranga** · 07-07-2010, 07:02 AM

Next thing, what happen if I enter the value "hello" as my inputs in your code?

Please use code tags. Didn't you notice that I've edited your previous posts and added code tags? Unformated codes are really hard to read.