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