Initializing an object

The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the class constructor.

$\begin{lstlisting} // Class Declaration \par public class Dog { // Instance Var... ...n'', 5, ''white''); System.out.println(tuffy.toString()); } } \end{lstlisting}$

Output:

$\begin{lstlisting} Hi my name is tuffy. My breed,age and color are papillon,5,white \end{lstlisting}$

This class contains a single constructor. We can recognize a constructor because its declaration uses the same name as the class and it has no return type. The Java compiler differentiates the constructors based on the number and the type of the arguments. The constructor in the Dog class takes four arguments. The following statement provides tuffy,papillon,5,white as values for those arguments:

$\begin{lstlisting} Dog tuffy = new Dog(''tuffy'',''papillon'',5, ''white''); \end{lstlisting}$

The result of executing this statement can be illustrated as :

**Figure 4.2:** Object model

All classes have at least one constructor. If a class does not explicitly declare any, the Java compiler automatically provides a no-argument constructor, also called the default constructor. This default constructor calls the class parent’s no-argument constructor (as it contain only one statement i.e super();), or the Object class constructor if the class has no other parent (as Object class is parent of all classes either directly or indirectly).