Very basic question regarding user input

[fugazi]

Hi there, I'm new to this forum and Java in general. I was just wondering if you can give me a little bit of help with my query on user input. I am pretty much a complete newbie and learning Java from the ground up so please bear with me.

Basically, what I am trying to do is give the user a choice of two options, and depending on what option they choose, the program will do one of two things.

All I have so far is the following:

import java.util.Scanner;

public class options
{

	public static void main (String[] args) 
	{
        Scanner scan = new Scanner(System.in);
        System.out.print("Please enter 'A' for option A, or 'B' for option 'B': ");
        String option = scan.nextLine();
        }

}

From there, I want the program to do either one thing or the other (I haven't decided what it will do yet!), depending on what option the user chooses. I understand this is about as basic as you can get

Any help would be greatly appreciated.

Many thanks
fugazi

[KevinWorkman]

Methinks you're looking for an if statement?

String animal = "cat";

if(animal.equals("cat")){
   System.out.println("Meow!");
}
else if(animal.equals("tribble"){
   System.out.println("trill, trill, purr, purr");
}
else{
   //...
}

[JosAH]

Well, the user typed something, pressed enter and the result ends up as a String value named 'option'. You can do with that String whatever you want, e.g.

if (option == null) 
   // the user typed an end-of-fIle key combination
// get rid of any leading and trailing white space
option= option.trim();
if (option.length() == 0)
   // the user just pressed the enter key
if (option.charAt(0) == 'A')
   // the user typed an A
...

It's up to your imagination to do with the input what you want.

kind regards,

Jos

[fugazi]

Many thanks Kevin for your very prompt reply!

I had been messing around with the if statement but my condition left a lot to be desired:

if(option = ("A"))

Like I said, I'm a complete newbie. I should hopefully now be able to make some progress!

Thanks again
fugazi

[fugazi]

Thank you Jos for your informative reply.

[KevinWorkman]

Many thanks Kevin for your very prompt reply!

I had been messing around with the if statement but my condition left a lot to be desired:

if(option = ("A"))

Like I said, I'm a complete newbie. I should hopefully now be able to make some progress!

Thanks again
fugazi

Well, you're making two mistakes there.

First off, assignment is done with a single equals sign, but equality is checked with two equals signs:

int i = 0;
if(i == 0){
//...

Second off, when dealing with Objects, testing for equality using == is testing whether the references are equal, not the content. Instead, use .equals when testing for an Object's content.

This might demonstrate what I mean:

Integer i = new Integer(7);
Integer j = new Integer(7);
System.out.println(i == j); //false, because they are not the same instance
System.out.println(i.equals(j)); //true, because they have the same content

This is especially troublesome with Strings because of the String pool, as == might actually work some of the time, leading you to believe that everything is hunky dory when in fact it is not.

Hope that helps.

[JosAH]

This might demonstrate what I mean:

Integer i = new Integer(7);
Integer j = new Integer(7);
System.out.println(i == j); //false, because they are not the same instance
System.out.println(i.equals(j)); //true, because they have the same content

This is especially troublesome with Strings because of the String pool, as == might actually work some of the time, leading you to believe that everything is hunky dory when in fact it is not.

Hope that helps.

It sure helps; but have a look at this (a continuation of your example)

System.out.println(i == 7); // true because of that nasty auto boxing

Maybe we'd better shouldn't uncover this tricky stuff ;-)

kind regards,

Jos