CODEWITHSUNDEEP
javaio
mooglin
mooglin

Reputation: 534

How to write the Java hasNext() function for custom scanners

I've found a number of custom Scanner classes on the internet for fast Java IO, but none of them offer a custom hasNext() method implementation, so I don't know how to read data when input is of variable size.

Here's an example of one of these classes:

class Reader {
static BufferedReader reader;
static StringTokenizer tokenizer;

/** call this method to initialize reader for InputStream */
static void init(InputStream input) {
    reader = new BufferedReader(
                 new InputStreamReader(input) );
    tokenizer = new StringTokenizer("");
}

/** get next word */
static String next() throws IOException {
    while ( ! tokenizer.hasMoreTokens() ) {
        //TODO add check for eof if necessary
        tokenizer = new StringTokenizer(
               reader.readLine() );
    }
    return tokenizer.nextToken();
}

static int nextInt() throws IOException {
    return Integer.parseInt( next() );
}

static double nextDouble() throws IOException {
    return Double.parseDouble( next() );
}
}

How could I go about writing this myself? Thanks.

Upvotes: 1

Views: 192

Answers (1)

Omar Emad
Omar Emad

Reputation: 78

Unfortunately the BufferedReader doesn't have a hasNext() function but it includes a ready() function which is a boolean function that tells if there is an input to be read or not, You can find about it here https://docs.oracle.com/javase/8/docs/api/java/io/BufferedReader.html#ready-- .

So if you want to added to the class you mentioned it will go like this :

static boolean ready() throws IOException {return reader.ready();}

However take care if the input is not present ready() will return false.

Upvotes: 2

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