created a static variable to make spelling mistakes harder to make when

assigning values to the "prAvAvail" attribute. 

src/main/java/ch/ethz/matsim/projects/astra_2018_002/av/AssignPrivatAVs.java

@@ -20,6 +20,7 @@ public class AssignPrivatAVs {
 		Config config = ConfigUtils.loadConfig(args[0]);
 		Scenario scenario = ScenarioUtils.loadScenario(config);
 		Random random = new Random(1);
+		final String AV_AVAILABILITY_ATTRIBUTE = "prAvAvail";
 
 		for (Person person : scenario.getPopulation().getPersons().values()) {	
 			String carAvailability = (String) person.getAttributes().getAttribute("carAvail");
@@ -41,27 +42,27 @@ public class AssignPrivatAVs {
 				
 					if (r <= 0.4200) {//produces "true" 42.05% of the time
 					
-						person.getAttributes().putAttribute("prAvAvail","car");
+						person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE,"car");
 						person.getAttributes().putAttribute("carAvail", "true");
 					
 					} else if (r <= 0.66) {//produces "true" 65.91% of the time: because the first step took 42.05% of the agents already,
 						// then this step will only consider the next 23.86% of agents
 					
-						person.getAttributes().putAttribute("prAvAvail","prav3");
+						person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE,"prav3");
 						person.getAttributes().putAttribute("carAvail", "false");
 					
 					} else if (r <= 0.82){
-						person.getAttributes().putAttribute("prAvAvail","prav4");
+						person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE,"prav4");
 						person.getAttributes().putAttribute("carAvail", "false");
 					
 					} else {
-						person.getAttributes().putAttribute("prAvAvail","prav5");
+						person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE,"prav5");
 						person.getAttributes().putAttribute("carAvail", "false");
 					}
 				
 				} else {  // make sure that those agents who "never" have a car available also do not have an private av available,and to 
 					// prevent "null" exceptions from Java, which occur when a variable, such as the attribute "pAvail
-					person.getAttributes().putAttribute("prAvAvail","noPrav");
+					person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE,"noPrav");
 					person.getAttributes().putAttribute("carAvail", "false");
 				}
 				
@@ -77,7 +78,7 @@ public class AssignPrivatAVs {
 						
 						if (leg.getMode().equals("car")) {
 							//need to make sure Mode is not zero, otherwise java will throw an error
-							leg.setMode((String) person.getAttributes().getAttribute("pAvAvail"));
+							leg.setMode((String) person.getAttributes().getAttribute(AV_AVAILABILITY_ATTRIBUTE));
 						}
 					}
 				}
@@ -92,7 +93,7 @@ public class AssignPrivatAVs {
 						
 						if (leg.getMode().equals("car")) {
 							//need to make sure Mode is not zero, otherwise java will throw an error
-							leg.setMode((String) person.getAttributes().getAttribute("pAvAvail"));
+							leg.setMode((String) person.getAttributes().getAttribute(AV_AVAILABILITY_ATTRIBUTE));
 						}
 					}
 				}
@@ -101,13 +102,13 @@ public class AssignPrivatAVs {
 			
 			 //##code that assigns all persons with carAvail == "always" or "sometimes" an AV##
 			/*if( carAvailability.equals(string1)) 
-				person.getAttributes().putAttribute("pAvAvail", "true");
+				person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE, "true");
 				
 				else if( carAvailability.equals(string2))
-					person.getAttributes().putAttribute("pAvAvail", "true");
+					person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE, "true");
 			
 				else
-					person.getAttributes().putAttribute("pAvAvail", "false");
+					person.getAttributes().putAttribute(AV_AVAILABILITY_ATTRIBUTE, "false");
 		*/