UnitTerm.java

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package cedar.hepdata.util;

import java.util.regex.Pattern;
import java.util.regex.Matcher;

import org.apache.log4j.*;


public class UnitTerm {
    public BaseUnit baseunit;

    public SiPrefix prefix;

    public Integer power;

    // Get a log4j logger
    static Logger log = Logger.getLogger(UnitTerm.class);


    public UnitTerm(BaseUnit baseunit, SiPrefix prefix, Integer power) {
        this.baseunit = baseunit;
        this.prefix = prefix;
        this.power = power;
    }

    public UnitTerm(UnitTerm otherterm) {
        this.baseunit = otherterm.baseunit;
        this.prefix = otherterm.prefix;
        this.power = otherterm.power;
    }

    public UnitTerm(String termstr) throws HDUnitException {
        fromString(termstr);
    }


    public UnitTerm fromString(String termstr) throws HDUnitException {
        prefix = null;
        baseunit = null;
        power = null;
        for (BaseUnit bu : BaseUnit.values()) {
            String baseunitMatches = "("
                + bu.toString() + "|"
                + bu.toString().toUpperCase() + "|"
                + bu.toString().toLowerCase() + ")";
            String regex = "\\A(/?)" // division indicator
                + "([YZEPTGMkmunpfazy]?)" // SI prefix patterns
                + baseunitMatches // base unit patterns
                + "(|[-+]\\d+|[E\\^][-+]?\\d+|\\*\\*[-+]?\\d+)\\Z"; // exponent patterns
            log.debug(regex);
            Pattern p = Pattern.compile(regex);
            Matcher m = p.matcher(termstr);
            if (m.matches()) {
                // Base unit
                baseunit = bu;
                // SI prefix
                final String prefixstr = m.group(2);
                for (SiPrefix testprefix : SiPrefix.values()) {
                    //log.trace(prefixstr + " vs. " + testprefix.toString());
                    if (testprefix.toString().equals(prefixstr)) {
                        prefix = testprefix;
                        break;
                    }
                }

                // Power
                String exppart = m.group(4).replaceAll("[\\*\\^E]", "");
                if (exppart.length() == 0) exppart = "1";
                try {
                    power = Integer.parseInt(exppart);
                } catch (Exception e) {
                    String err = "Could not build a valid unit term from '" + termstr + "'. ";
                    err += "Problem with exponent part '" + exppart + "'.";
                    throw new HDUnitException(err);
                }
                // Finally, invert the power if this was a division term
                if (m.group(1).length() != 0) {
                    power = -power;
                }

                // Stop looping over base units
                break;
            }
        }
        log.debug(prefix + " " + baseunit + " " + power);
        if (prefix == null || baseunit == null || power == null) {
            throw new HDUnitException("Could not build a valid unit term from '" + termstr + "'");
        }
        log.info(termstr + " -> [" + prefix.toString() + ", " + baseunit.toString() + ", " + power + "]");
        return this;
    }

    public Double convFactor() {
        return Math.pow(10.0, new Double(prefix.powerOf10() * power));
    }

    public String toString() {
        StringBuffer s = new StringBuffer();
        s.append(this.prefix.toString());
        s.append(this.baseunit.toString());
        if (this.power != 1) {
            s.append("^" + this.power);
        }
        return s.toString();
    }

    // Override default equals
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (! (obj instanceof UnitTerm)) return false;
        UnitTerm test = (UnitTerm) obj;
        if (! test.baseunit.equals(this.baseunit) ) return false;
        if (! test.prefix.equals(this.prefix) ) return false;
        if (! test.power.equals(this.power) ) return false;
        return true;
    }
}

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