Java , storing strings into an array

Question

I wish to put the raw questions(rawQuestions) as inputted in this way in command prompt: java Hangman Hello test 123, into the array (questions). I know rawQuestion will not work down in the "store valid questions into an array" part because of

• "error: ';' expected " and "error: not a statement"

in the line

• " questions[vCount] = String rawQuestion; "

Therefore how should I rewrite it?

public class Hangman {

    //Validation of raw questions

    public static boolean isValidQuestion(String rawQuestion){
        rawQuestion = rawQuestion.toUpperCase();
        boolean vQuestion = true;
        for(int i=0; i<rawQuestion.length(); i++){
            char c = rawQuestion.charAt(i);

            if(!(c>='A' && c<='Z'))
            vQuestion = false;
        }
        return vQuestion;
    }


    public static void main(String args[]){

        boolean vQs[] = new boolean[args.length];

        for(int i=0; i<args.length; i++){

            String rawQuestion = args[i];

            boolean b = isValidQuestion(rawQuestion);

            if(b)
                 System.out.println(rawQuestion + " is a valid question!");

            else
                 System.out.println("Error: " + rawQuestion + ", input must be a word consist of a-z or A-Z");

            vQs[i] = b;
        }

        //count the number of valid questions

        int vCount = 0;
        for(int i=0; i<vQs.length; i++){
            System.out.println(i + " " + vQs[i] );
            if(vQs[i])
                vCount++;
        }
        System.out.println("There are " + vCount + " valid questions");

        //store valid questions into an array

        String questions[] = new String[vCount];
        for(vCount=0; vCount<args.length; vCount++){
            questions[vCount] = String rawQuestion;
            System.out.println( questions[vCount] );


        }

    }
}

Answer 1

Try this:

String[] validQuestions = Arrays.stream(args)
                                .filter(Hangman::isValidQuestion)
                                .toArray(String[]::new);
int validQuestionCount = validQuestions.length;

But even without Streams, your whole method could be done in one for loop, counting and collecting the valid questions in one go instead of having three separate steps:

List<String> validQuestions = new ArrayList<>();
for (int i = 0; i < args.length; i++)
{
    String rawQuestion = args[i];
    boolean b = isValidQuestion(rawQuestion);
    if (b)
    {
        validQuestions.add(rawQuestion);
        System.out.println(rawQuestion + " is a valid question!");
    }
    else
    {
        System.out.println("Error: " + rawQuestion + ", input must be a word consist of a-z or A-Z");
    }
}

// count the number of valid questions
System.out.println("There are " + validQuestions.size() + " valid questions");

// store valid questions into an array
String questions[] = validQuestions.toArray(new String[validQuestions.size()]);

This way, you do not have to juggle the index variables yourself, which is hard to understand, especially if somebody else tries to read it. (Especially the re-use of vCount is kinda scary to me)

Answer 2

I fixed something and commented, not sure if it works, i haven't compiled it.

public static void main(String args[]){

boolean vQs[] = new boolean[args.length];
int vCount=0;

for(int i=0; i<args.length; i++){

    String rawQuestion = args[i];

    if(isValidQuestion(rawQuestion)){


    System.out.println(rawQuestion + " is a valid question!");
            //Here you have enough data to count the valid questions, three loops are not needed.
            ++vCount;
            vQs[i]=true;
        }else{
            System.out.println("Error: " + rawQuestion + ", input must be a word consist of a-z or A-Z");
            vQs[i]=false;
        }
    }

    System.out.println("There are " + vCount + " valid questions");

    //store valid questions into an array
    String questions[] = new String[vCount];

    int j=0;
    for(int i=0; i<args.length; i++){
        //You need to iterate for all strings, because vQs[] is long args.length
        if(vQs[i]){
            //Ok the i-th question was valid, let's move it and print it
            questions[j] = args[i];
            System.out.println( questions[j] );
            ++j;
        }
    }

}

}