Question

I want to do something like this:

Creator method = new Creator();
method.addSubject("example");

class Creator{
  public void addSubject(String subjName) {
     //here is the issue
     subjName = new Subject(subjName);
  }
}

class Subject {
  private String name;
  public Subject(String newName) {
    name = newName;
  }
}

So I want this class called Creator to be able to make Subjects, but I need it to be able to do so by passing it a String with the name that I want to call those subjects. How can I do this?

Edit: To clarify, the class “Creator” has a method called “addSubject”. In the main method of the program I have an object of Creator called “method” (probably should have chosen a better example name). So can this object of Creator make objects of another class, class “Subject”, simply by passing the method “addSubject” the name I want those objects of Subject to have?

Edit2: This is the pseudocode of what I want:

Main method:
Initialize Creator object
Command line for program takes arguments
Pass these arguments to creator object

Creator Object:
Takes command line argument in the form of string and makes a new object of the class Subject by the name of the String

Answer 1

I think you want to create a new object of a class that you just want to use the name. Is it? So, you can do this (Java 7).

try {
    // you need to provide the default constructor!
    Object newInstance = Class.forName( "your.package.YourClassName" ).newInstance();
} catch ( ClassNotFoundException | IllegalAccessException | InstantiationException exc ) {
    exc.printStackTrace();
}

If you are using a Java version prior to 7, you need to use 3 catch statements, one for ClassNotFoundException, one for IllegalAccessException and one for InstantiationException.

Edit: I think I understood now. You want to create instances of Subject with a name passed to the method. You can use a HashMap to simulate this.

Something like:

import java.util.*;

class Creator{

  private Map<String, Subject> map = new HashMap<String, Subject>();

  public void addSubject(String subjName) {
     map.put( subjName, new Subject(subjName) );
  }

  public Subject getSubject(String subjName) {
     return map.get(subjName);
  }
}

class Subject {
  private String name;
    public Subject(String newName) {
      name = newName;
    }
    @Override
    public String toString() {
      return name;
    }
}

// using...
Creator method = new Creator();
method.addSubject("example");

// prints example
System.out.println( method.getSubject("example") );

// prints null, since there is not a value associeted to the "foo" 
// key in the map. the map key is your "instance name".
System.out.println( method.getSubject("foo") );