Java Community | Help. Code. Learn.•2mo ago

Problem with own Scanner's methods

I need to realise simple version of scanner for much faster reading. I must use block reading available from Reader and its buffer. I can't get how to make hasNext methods (at least hasNext and hasNextInt) due to the problem, that if next appropriate answer is lay in some buffers and input is keyword I will lost intermediate buffers as i cant reread system input. also as i understand using linkedhashmap or String for intermediate buffers can cost a lot of memory if answer is lay in a few million buffers. can someone tell it is more sensible to realise these methods i have such realisation now(sorry if someone thinks that i have bad or cumbersome code, i m a newbie in java)

public class MyScanner {
    private char[] buffer = new char[4096];
    private Reader in;
    private int position = 0;
    private int read = 0;
    
    public MyScanner(String inputFile) throws IOException {
        this.in = new InputStreamReader(
                new FileInputStream(inputFile), "utf8"
            );    
    }
    
    public MyScanner(InputStream input) {
        this.in = new InputStreamReader(input);
    }
    
    private String getNext(String token) {
        StringBuilder chars = new StringBuilder();
        StringBuilder remainder = new StringBuilder();
        if (position == 0) {
            read = in.read(buffer);
        } 
        while (read >= 0) {
                     ..... //logic of checking symbols
        }

public class MyScanner {
    private char[] buffer = new char[4096];
    private Reader in;
    private int position = 0;
    private int read = 0;
    
    public MyScanner(String inputFile) throws IOException {
        this.in = new InputStreamReader(
                new FileInputStream(inputFile), "utf8"
            );    
    }
    
    public MyScanner(InputStream input) {
        this.in = new InputStreamReader(input);
    }
    
    private String getNext(String token) {
        StringBuilder chars = new StringBuilder();
        StringBuilder remainder = new StringBuilder();
        if (position == 0) {
            read = in.read(buffer);
        } 
        while (read >= 0) {
                     ..... //logic of checking symbols
        }

10 Replies

JavaBot•2mo ago

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dan1st•2mo ago

Depending on what you for your hasNext methods, you may not need a large buffer between methods and if you need a bigger buffer locally (within one method), that can likely be optimized (at least if the method is used very frequently)

JavaBot•2mo ago

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KnightElf•2mo ago

Hi, My name is Lukas and I'm proficient in Java. I read your post and I think I can help you.

KnightElf•2mo ago

check this code

scanner.java

KnightElf•2mo ago

I hope this can help you

flechergameOP•2mo ago

wow, it is almost ideally what i need, i will try to add checking special word patterns in it, thank you a lot, I can't contain my joy

JavaBot•2mo ago

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KnightElf•2mo ago

You're welcome is it working?

JavaBot•2mo ago

💤 Post marked as dormant

This post has been inactive for over 300 minutes, thus, it has been archived. If your question was not answered yet, feel free to re-open this post or create a new one. In case your post is not getting any attention, you can try to use /help ping. Warning: abusing this will result in moderative actions taken against you.

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Problem with own Scanner's methods

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