udunits/src/main/java/ucar/units/PrefixDBImpl.java
public void addSymbol(final String symbol, final double value)
			throws PrefixExistsException {
		final Prefix prefix = new PrefixSymbol(symbol, value);
		symbolSet.add(prefix);
		valueMap.put(new Double(value), prefix);
	}
public void addSymbol(final String symbol, final double value)
			throws PrefixExistsException {
		final Prefix prefix = new PrefixSymbol(symbol, value);
		symbolSet.add(prefix);
		valueMap.put(new Double(value), prefix);
	}
Adds a prefix symbol to the database.

@param symbol
The symbol of the prefix to be added.
@param value
The value of the prefix.
@throws PrefixExistsException
Another prefix with the same symbol or value already exists
in the database.