Using variables outside while loops in java

Question

I'am trying to write a program in Java that collects users favorite names within an array and then prints these names at the end.

NOTE: the length of the array should be defined by the number of names a user enters.

Please take a look at the code and tell me how to fix it. Here is what I have done so far

Scanner input = new Scanner(System.in);

System.out.println("What are your most favorite names?");
        
String[] favNames = new String[i];
int i = 1;
            
while (true){
    System.out.print("Please enter favorite name number" + i + ":  ");
    favNames[i-1] = input.next();
    System.out.print("Is that all?");
    String ans = input.next().toLowerCase();
    if(ans.startsWith("y")){
        System.out.print("Here is the completed list of your favorite names:\n" + Arrays.toString(favNames));
        break;
    }
    i++;
}

This is the error code I get:

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - cannot find symbol
symbol: variable i
location: class JavaApplication13
at JavaApplication13.main(JavaApplication13.java:52)
Java Result: 1

I tried moving the first parts of the code inside the loop but it only prints one of the names the user enters.

//These parts:
String[] favNames = new String[i];
int i = 1;

If I swap the places between the first and second line. The array gets only 1 entry from the user.

//Only gets one entry
int i = 1;
String[] favNames = new String[i];

Aman · Accepted Answer · 2020-11-15 22:13:09Z

1

Variables should be declared before use. This is why your program is not working.

Change

String[] favNames = new String[i];
int i = 1;

To

int i = 1;
String[] favNames = new String[i];

But, keep in mind that in this case the used can only input 1 time(because arrays have fixed size). If you want to use an arbitrary number of input, you have to use ArrayList or similar types.

edited Nov 15, 2020 at 22:13

answered Nov 15, 2020 at 22:06

Aman

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Comments

geocodezip · Accepted Answer · 2020-11-15 22:43:39Z

declare variables before using them:

        int i = 1;
        String[] favNames = new String[i];

However, an array of size 1, will only work for 1 entry. If you would like the user to be able to enter more than that you need a bigger array.

I would suggest an arbitrarily large size (say 100), then check that the entry fits in the array; if it doesn't, game over.


String[] favNames = new String[100];

int i = 1;
while (true) {
    System.out.print("Please enter favorite name number" + i + ":  ");
    favNames[i - 1] = input.next();
    System.out.print("Is that all?");
    String ans = input.next().toLowerCase();
    if (ans.startsWith("y")) {
        System.out.print("Here is the completed list of your favorite names:\n" + Arrays.toString(favNames));
        break;
    }
    i++;
    if (i > favNames.length)
        System.out.print("Can't accept more than "+favNames.length+" entries, here is the completed list of your favorite names:\n" + Arrays.toString(favNames));
}

The issue then is that Arrays.toString will print null for the empty entries.

I would make a custom routine to print the array that ends on the first null:


static String printFavNames(String[] favNames) {
    String output = "[";
    for (String s : favNames) {
        if (s==null)
            break;
        if (output.length() > 1)
            output += ", ";
        output += s;
    }
    output += "]";
    return output;
}

related question: How to print all non null elements of an array using Array.toString()

full code:

import java.util.Scanner;

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

        Scanner input = new Scanner(System.in);

        System.out.println("What are your most favorite names?");

        String[] favNames = new String[100];

        int i = 1;
        while (true) {
            System.out.print("Please enter favorite name number" + i + ":  ");
            favNames[i - 1] = input.next();
            System.out.print("Is that all?");
            String ans = input.next().toLowerCase();
            if (ans.startsWith("y")) {
                System.out.print("Here is the completed list of your favorite names:\n" + printFavNames(favNames));
                break;
            }
            i++;
            if (i > favNames.length)
                System.out.print("Can't accept more than "+favNames.length+" entries, here is the completed list of your favorite names:\n" + printFavNames(favNames));
        }
        input.close();
    }
    static String printFavNames(String[] favNames) {
        String output = "[";
        for (String s : favNames) {
            if (s==null)
                break;
            if (output.length() > 1)
                output += ", ";
            output += s;
        }
        output += "]";
        return output;
    }
}

Thanks a lot!<br> The assignment question asked me to create an array which its length is defined by the user.<br>
That wasn't in the question. You were still creating an array of size 1, not a size defined by the user, rather than using 1, ask the user for the size.

AntonioKaram · Accepted Answer · 2020-11-15 21:34:40Z

0

Just move the i++ to inside the while loop and all be good!

answered Nov 15, 2020 at 21:34

AntonioKaram

315 bronze badges

1 Comment

M. Steiner Over a year ago

thank u for the comment! but it doesn't still work.

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