parse.java

import java.lang.Math; // headers MUST be above the first class
import java.util.ArrayList;

// one class needs to have a main() method
public class HelloWorld
{
  // arguments are passed using the text field below this editor
  public static void main(String[] args)
  {
    Persons p = new Persons("John;27;\nPeter;22;");
    // Change peters age to 30
    p.persons.get(1).age = 30;
    // Print the result
    System.out.println(p.save());
  
  }
}

// you can add other public classes to this editor in any order
public class Person
{
	public String name;
  	public int age;
  	
  	public Person(String line){
      	String[] content = line.split(";");
      	name = content[0];
      	age = Integer.parseInt(content[1]);
  	}
}

public class Persons {
	public ArrayList<Person> persons;
  
  	public Persons(String file){
      	ArrayList<Person> persons = new ArrayList<Person>();
  		String[] lines = file.split("\\r?\\n");
      	for (String line : lines) {
          	Person p = new Person(line);
          	persons.add(p);
      	}
      	this.persons = persons;
    }
  
  	public String save() {
      	String s = "";
      	for (Person person : persons) {
      		s += person.name + ";" + person.age + ";\n";
      	}
      	return s;
  	}
}