How can I do this in java?

• DynamicNavStack(int cap): This constructor takes as an argument the initial capacity of the array and allocates memory for that array. If the argument is either 0 or a negative integer, set the initial capacity of the array to the default capacity (=2). Other member variables are assigned as appropriate.
• DynamicNavStack(): This constructor should use the other constructor with an initial capacity set to default value(=2).

public class DynamicNavStack //this is my class name

private E[] navStack; //and this is my stack