I am having trouble instantiating a class using Class.forName(). At first, I was trying to create the class by using just the class name but it kept on throwing "ClassNotFoundError". So, I added the package name but the format for me is package$className. E.g:
`Class<?> cls = Class.forName("GreenhouseControls$ThermostatNight"); //` This Works.
I read class names that need to be instantiated from a file. Once the class created, I add the event using the addEvent() function from the controller class.
Unfortunately, when I try to get the constructor to instantiate the class, I get a "NoSuchMethodError". I am not sure why? I am wondering if it's the abstract class that is not allowing me to get the subclass constructor?
GreenhouseControls.java
import java.io.*;
import java.lang.reflect.*;
import java.lang.Long;
import java.util.*;
import java.util.regex.*;
import tme3.*;
public class GreenhouseControls extends Controller{
public class ThermostatNight extends Event {
public ThermostatNight(long delayTime) {
super(delayTime);
}
public void action() {
// Put hardware control code here.
thermostat = "Night";
}
public String toString() {
return "Thermostat on night setting";
}
}
public class Restart extends Event {
public Restart(long delayTime, String filename) {
super(delayTime);
eventsFile = filename;
}
public void action() {
File f = new File(eventsFile);
try{
Scanner scan = new Scanner(f);
Pattern class_name = Pattern.compile("(?<==)(.*)(?=,time)");
Pattern time1 = Pattern.compile("(?<=time=)(.*)(?=,*)");
Pattern rings_time = Pattern.compile("(?<=time=)(.*)(?=,)");
Pattern rings = Pattern.compile("(?<=rings=)(.*)");
while(scan.hasNextLine()){
String event_name;
long l;
int r = 0;
Class<?> cls;
Constructor<?> clsCon;
event_name = scan.findInLine(class_name)
try{
String check = scan.findInLine(rings_time);
check.getClass();
l = Long.valueOf(check).longValue();
r = Integer.valueOf(scan.findInLine(rings)).intValue();
}catch(NullPointerException e){ l = Long.valueOf(scan.findInLine(time1)).longValue(); }
System.out.println("event_name: " + event_name + " Time: " + l + " Rings: " + r);
cls = Class.forName("GreenhouseControls$ThermostatNight");
clsCon = cls.getDeclaredConstructor(); // This Code throws and error because apparently there is no constructor
if (scan.hasNextLine())
scan.nextLine();
}
}catch(Exception e) { System.out.println(e); }
//addEvent(new ThermostatNight(0));
}
}
public static void main(String[] args) {
try {
String option = args[0];
String filename = args[1];
if ( !(option.equals("-f")) && !(option.equals("-d")) ) {
System.out.println("Invalid option");
printUsage();
}
GreenhouseControls gc = new GreenhouseControls();
if (option.equals("-f")) {
gc.addEvent(gc.new Restart(0,filename));
}
gc.run();
}
catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Invalid number of parameters");
printUsage();
}
}
}
Event.java
package tme3;
import java.io.*;
public abstract class Event {
private long eventTime;
protected final long delayTime;
public Event(){ delayTime = 0;}
public Event(long delayTime) {
this.delayTime = delayTime;
start();
}
public void start() { // Allows restarting
eventTime = System.currentTimeMillis() + delayTime;
}
public boolean ready() {
return System.currentTimeMillis() >= eventTime;
}
public abstract void action();
}
}
Controller.java
public class Controller {
// A class from java.util to hold Event objects:
private List<Event> eventList = new ArrayList<Event>();
public void addEvent(Event c) { eventList.add(c); }
public void run() {
while(eventList.size() > 0)
// Make a copy so you're not modifying the list
// while you're selecting the elements in it:
for(Event e : new ArrayList<Event>(eventList))
if(e.ready()) {
System.out.println(e);
e.action();
eventList.remove(e);
}
}
}
