Using string as name for objects in Java

Question

Okay so I have the following piece of code:

Random rnd = new Random();
int i = 0;
while(i<1000) {
  String name = "event" + i;
  Event name = new Event(rnd.nextInt(100000)); //ERROR duplicate variable
  SimEngine.getScheduler().addEventToQueue(event);
  i++;
}
System.out.println(SimEngine.getScheduler().getQueue().iterator());

I know that declaring name twice makes no sense, but I hope you can see what I'm trying to do. Because I want Event objects with names event1, event2 ,event3 etc.

How can I get it to let me use the String name as the name of the Event object?

Jon Skeet · Accepted Answer · 2012-11-10 15:21:54Z

6

Because I want Event objects with names event1, event2 ,event3 etc.

Objects don't (typically) have names. Variables have names. You really don't want to have variables with names event1, event2 etc though.

In this case, you should basically use an array, if you really need to have access to the events by index.

Event[] events = new Event[1000];
for (int i = 0; i < 1000; i++) {
    events[i] = new Event(rnd.nextInt(100000));
    SimEngine.getScheduler().addEventToQueue(events[i]);
}

Of course, if you're not going to use the variable afterwards, it's pointless anyway, and you'd be just as well off with:

for (int i = 0; i < 1000; i++) {
    SimEngine.getScheduler().addEventToQueue(new Event(rnd.nextInt(100000));
}

If this particular kind of class does have a name associated with each instance, you'd need to pass that name into the constructor, I suspect.

answered Nov 10, 2012 at 15:21

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Force444 Over a year ago

Thank you very much! Both solutions are helpful, but as I'm not really going to be using each Event object afterwards anyway, I'll go with the second approach. :)

amit · Accepted Answer · 2012-11-10 15:22:17Z

4

You cannot¹, but you can use a Map<String,Event> instead, and put your variable names as the keys and the objects as the values.

To access the "variables" - you can use Map.get() and Map.put(). Something along the lines of:

Map<String,Event> varaibles = new HashMap<String,Event>();
variables.put("event" + i, new Event(...)) //setting new "varaibles"
Event myEvent = variables.get(someString); //getting the objects assigned to a "variable"

(1) It could partially be done with reflection. If you have the variables already (not declaring new ones) - you can access a variable by its name using the reflection API, but it is unadvised.

answered Nov 10, 2012 at 15:22

amit

179k27 gold badges245 silver badges348 bronze badges

Comments

James Lim · Accepted Answer · 2012-11-10 15:22:44Z

1

Use an array, or a hash table.

Map<String, Event> m = new HashMap<String, Event>();

You cannot (at least not easily) set variable names during runtime.

answered Nov 10, 2012 at 15:22

James Lim

13.1k4 gold badges44 silver badges66 bronze badges

Comments

Moataz Elmasry · Accepted Answer · 2012-11-10 15:24:07Z

1

you don't have to name each object in order to use a series of them, that's what data structures are for, ex array or map so you can do something like

SimEngine.getScheduler().addEventToQueue(new Event(rnd.nextInt(100000)));

is that what you want?

answered Nov 10, 2012 at 15:24

Moataz Elmasry

2,5194 gold badges28 silver badges39 bronze badges

Collectives™ on Stack Overflow

Using string as name for objects in Java

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related