package org.lcsim.units;
   
   import java.lang.reflect.Field;
   import java.util.HashMap;
   import java.util.Map;
   import java.util.Set;
   import java.util.Map.Entry;
   
   public class Constants 
  {
  	Map<String, Double> constantsMap = new HashMap<String, Double>();
  
  	private static Constants instance = new Constants();
  
  	public double get(String key)
  	{
  		return constantsMap.get(key);
  	}
  
  	public Set<Entry<String,Double>> entrySet()
  	{
  		return constantsMap.entrySet();
  	}
  
  	public static Constants getInstance()
  	{
  		return instance;
  	}
  
  	private Constants()
  	{
  		setupSystemOfUnits();
  	}
  
  	private void setupSystemOfUnits()
  	{
  		SystemOfUnits units = new SystemOfUnits();      
  		Class<SystemOfUnits> klass = SystemOfUnits.class;
  		Field[] fields = klass.getFields();
  		for (Field f : fields)
  		{
  			try {
  				constantsMap.put(f.getName(), f.getDouble(units));
  			}
  			catch ( IllegalAccessException x )
  			{
  				throw new RuntimeException(x);
  			}
  		}
  	}
  }