Constructors are used to initializing the variables. Following example helps in better understanding.

Java Code:
public class Lab {
private int id;
private String name;
private String category;
private Date dateOfConst;

public Lab(int id, String name, String category, Date dateOfConst)
{
	this.id = id;
	this.name = name;
	this.category = category;
	this.dateOfConst = dateOfConst;
	}

}