Parse.java

import java.util.ArrayList;


class HelloWorld
{
	public static void main(String[] args)
	{
		String input = "John;27;\nPeter;22;";
		System.out.println("Input:");
		System.out.println(input);
		System.out.println("");
		Persons p = new Persons(input);
		// Change peters age to 30
		p.persons.get(1).age = 30;
		// Print the result
		System.out.println("Output:");
		System.out.println(p.save());

	}
}

class Person
{
	public String name;
	public int age;

	public Person(String line){
		String[] content = line.split(";");
		name = content[0];
		age = Integer.parseInt(content[1]);
	}
}

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;
	}
}