anyone know java?

[SuperBowlNachos]

I need help on my java again. I suck at this stuff.

I have to make a program that lets a user select between 4 options and then choose a distance of their choosing. It's trying to figure out how fast sound travels through certain objects. I have to have a demo program and a separate class.

As you will see I have a lot of repeating calculations. I'm just not sure what needs to be where, and I am not sure of what the output statement should be.

public class Sound

{
	private final double air = 1100;
	private final double water = 4900;
	private final double steel = 16400;
	double distance;
	double time;

	// no arg constructor

	public Sound()
	{
		distance = 0.0;
	}

	//parameterized constructor

	public Sound(double d)
	{
		distance = d;
	}

	//mutator methods

	public void setDistance(double d)
	{
		distance = d;
	}

	//accessor methods

	public double getSpeedInAir()
	{
		return distance / 1100;
	}

	public double getSpeedInWater()
	{
		return distance / 4900;
	}

	public double getSpeedInSteel()
	{
		return distance / 16400;
	}
}

	import java.util.Scanner;
	import java.text.DecimalFormat;

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

	{

		double choice;
		double time;
		double distance;

		Scanner keyboard = new Scanner(System.in);


		System.out.print("Please choose 1. Air 2. Water 3. Steel 4. Quit ");
		choice = keyboard.nextDouble();

		System.out.print("What distance would you like to know? ");
		distance = keyboard.nextDouble();


	   if (choice.equals("1"))
			{
	     		time = (distance / 1100);
	   			System.out.println("The total time traveled is " + time + ".");
			}

		else if (choice.equals("2"))
			{
				time = (distance / 4900);
				System.out.println("The total time traveled is " + time + ".");
			}

		else if (choice.equals("3"))
			{
				time = (distance / 16400);
				System.out.println("The total time traveled is " + time + ".");
			}
		else if (choice.equals(" "))
			{
				System.out.println("Invalid input!");
			}


}
}

[ChampN252]

Re: anyone know java?

I'm no expert, but I'm trying to get this running and can't. I made my little java script file and tried running this thru FF and I'm having to luck. What should this look like in the file and what are you using to run this?

[ChampN252]

Re: anyone know java?

I see I had confused myself...maybe I should leave to for an actually "pro". GL

[SuperBowlNachos]

Re: anyone know java?

Textpad. You have to save them both to the same folder. First one should have no syntax errors, the second isn't complete. It won't run as a whole yet.

[stizz]

Re: anyone know java?

Your biggest problem is that you're trying to compare a double to a string. To compare a double you should have if (choice == 1) { do stuff }.

Another thing you could do as well is make the very last else if statement just an else statement. That way if they type anything other than 1,2,3 or 4 it'll print out your error message.

I also noticed that you haven't created a Sound object yet either.

You don't use your final variables either. In your Sound class, you should use the final variables instead of the numbers you type in.

I don't think you should have those computing methods inside your main either. Those should be calculated in the Sound class then you should call the methods on the Sound object you create.

[The GIGGAS]

Re: anyone know java?

Your biggest problem is that you're trying to compare a double to a string. To compare a double you should have if (choice == 1) { do stuff }.

Another thing you could do as well is make the very last else if statement just an else statement. That way if they type anything other than 1,2,3 or 4 it'll print out your error message.

I also noticed that you haven't created a Sound object yet either.

You don't use your final variables either. In your Sound class, you should use the final variables instead of the numbers you type in.

I don't think you should have those computing methods inside your main either. Those should be calculated in the Sound class then you should call the methods on the Sound object you create.

This is all good stuff.

[SuperBowlNachos]

Re: anyone know java?

Well apparently we are supposed to use switches. So this is where I am now at. Had a buddy helping me, but he had to go. He said I needed to add something to the class statements in the driver program, can't remember what though.

public class Sound

{

	double distance;


	// no arg constructor

	public Sound()
	{
		distance = 0.0;
	}

	//parameterized constructor

	public Sound(double d)
	{
		distance = d;
	}

	//mutator methods

	public void setDistance(double d)
	{
		distance = d;
	}


	//accessor methods

	public double getSpeedInAir()
	{
		return distance / 1100;
	}

	public double getSpeedInWater()
	{
		return distance / 4900;
	}

	public double getSpeedInSteel()
	{
		return distance / 16400;
	}
}

	import java.util.Scanner;
	import java.text.DecimalFormat;

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

	{

		Int choice;
		double distance;

		Scanner keyboard = new Scanner(System.in);


		System.out.print("Please choose 1. Air 2. Water 3. Steel 4. Quit ");
		choice = keyboard.nextDouble();

		if (choice != 1 && choice != 2 && choice != 3 && choice !=4)
		System.out.print("Please choose 1. Air 2. Water 3. Steel 4. Quit ");
		choice = keyboard.nextDouble();

		if(choice ==4)
		{
		System.exit(choice)
	}

		System.out.print("What distance would you like to know? ");
		distance = keyboard.nextDouble();

		switch(choice)

		class 1:

  	 			System.out.println("The total time traveled is " + time + ".");

		class 2:

				System.out.println("The total time traveled is " + time + ".");

		class 3:

				System.out.println("The total time traveled is " + time + ".");


}

[The GIGGAS]

Re: anyone know java?

Well apparently we are supposed to use switches. So this is where I am now at. Had a buddy helping me, but he had to go. He said I needed to add something to the class statements in the driver program, can't remember what though.

Your syntax for the switch statement is a bit off:

It should look like this:

   switch (choice)
   {
      case 1:
         sop...;
         break;
      case 2:
         sop...;
         break;
      case 3:
         sop...;
         break;
   }

http://download.oracle.com/javase/tutorial/java/nutsandbolts/switch.html

[SuperBowlNachos]

Re: anyone know java?

What does the break mean?

[p_rushing]

Re: anyone know java?

What does the break mean?

It breaks out of the switch case. It ends that current case statement and then exits the switch so you don't check the other cases, saving processing time. You also need to add a default case so that action is taken if their is a case that doesn't match anything.

[Blzer]

Re: anyone know java?

It breaks out of the switch case. It ends that current case statement and then exits the switch so you don't check the other cases, saving processing time. You also need to add a default case so that action is taken if their is a case that doesn't match anything.

To append to what he said, "switch" is essentially another way of using a bunch of if-else statements. The default case is your "else" in this scenario.

[stizz]

Re: anyone know java?

http://www.java2s.com/Tutorial/Java/CatalogJava.htm

This website has good tutorials for Java.

[SuperBowlNachos]

Re: anyone know java?

I ended up getting it. I'll post it next week when I am in class again.