https://github.com/hughperkins/jfastparser

Very fast parsing of doubles and ints from a string
https://github.com/hughperkins/jfastparser

Last synced: 4 months ago
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Very fast parsing of doubles and ints from a string

• Host: GitHub
• URL: https://github.com/hughperkins/jfastparser
• Owner: hughperkins
• License: mit
• Created: 2012-10-11T02:15:31.000Z (about 13 years ago)
• Default Branch: master
• Last Pushed: 2017-10-28T12:33:24.000Z (almost 8 years ago)
• Last Synced: 2025-05-13T02:12:35.699Z (5 months ago)
• Language: Java
• Size: 217 KB
• Stars: 16
• Watchers: 3
• Forks: 6
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
jfastparser

===========

Very fast parsing of doubles and ints from a string

Usage

=====

    String input = "123 56.4 12:3";

    Parser parser = new Parser(input);

    int v1 = parser.eatInt();

    parser.eatWhitespace();

    double v2 = parser.eatDouble();

    parser.eatWhitespace();

    double v3 = parser.eatDouble();

Concept

=======

Instantiate a Parser object with a string, call eat methods to progressively 'eat' the 

string.

Methods

=======

    parser.eatInt(); // eats an integer from the string, or throws 

                     // RuntimeException

    parser.eatDouble(); // eats double from the string, or throws 

                        // RuntimeException

    parser.eatChar(somechar); // eats somechar from the string, or throws 

                              // RuntimeException

    parser.eatWhitespace(); // eats any whitespace from the string from the 

                            // current position

    parser.more(); // is there anything else to read?

Performance

===========

Test: parse a string of doubles, created like this:

    StringBuilder builder = new StringBuilder();

    builder.append(0);

    int N = 1000000;

    for( int i = 1; i < N; i++ ) {

    builder.append(" " + ( i / 10.0 ) );

    }

    String line = builder.toString();

Code:

Scanner:

	byte[] bytes = line.getBytes();

	ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);

	Scanner scanner = new Scanner(byteArrayInputStream);

    while(scanner.hasNext()) {

	    double value =  scanner.nextDouble();

	    values[n] = value;

	    n++;

    }		

Split:

    String[] splitline = line.split(" " );

    for( String token : splitline ) {

	    double value =  Double.parseDouble(token);

	    values[n] = value;

	    n++;

    }

StringTokenizer:

    StringTokenizer stringTokenizer = new StringTokenizer(line);

    while( stringTokenizer.hasMoreTokens()) {

	    double value = Double.parseDouble( stringTokenizer.nextToken() );

	    values[n] = value;

	    n++;

    }		

JFastParser:

    parser = new Parser(line);

    while(parser.more()) {

	    double value =  parser.eatDouble();

	    parser.eatWhitespace();

	    values[n] = value;

	    n++;

    }		

Timings:

    Scanner: 10642 ms

    split: 715 ms

    StringTokenizer: 544ms

    JFastParser: 290ms