SISuffixHelper.java

package com.llamacorp.equate;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Helper class used to give the name equivelent of decades of numbers
 * For example 1E6 is mega, and E-9 is nano
 */
public class SISuffixHelper {
	private static final Map<String, String> mSISuffixMap;

	static {
		Map<String, String> aMap = new HashMap<>();
		aMap.put("E24",  "yotta");
		aMap.put("E21",  "zetta");
		aMap.put("E18",  "exa");
		aMap.put("E15",  "peta");
		aMap.put("E12",  "tera");
		aMap.put("E9",   "giga");
		aMap.put("E6",   "mega");
		aMap.put("E3",   "kilo");
		aMap.put("E2",   "hecto");
		aMap.put("E1",   "deca");
		aMap.put("E-1",  "deci");
		aMap.put("E-2",  "centi");
		aMap.put("E-3",  "milli");
		aMap.put("E-6",  "micro");
		aMap.put("E-9",  "nano");
		aMap.put("E-12", "pico");
		aMap.put("E-15", "femto");
		aMap.put("E-18", "atto");
		aMap.put("E-21", "zepto");
		mSISuffixMap = Collections.unmodifiableMap(aMap);
	}

	/**
	 * Get the SI unit name for the exponent attached to the given String
	 * representation of a number
	 *
	 * @param number given in string format
	 * @return SI unit name (for 2E9 return giga, for 1E-12 pico)
	 */
	public static String getSuffixName(String number) {
		//if we have more that one E for some reason, OR
		//if there is no E in the expression, leave
		if (number.matches(".*E.*E.*") || !number.contains("E")) return "";

		String result = mSISuffixMap.get(number.substring(number.indexOf("E")));

		if (result != null) return result;
		else return "";
	}
}