call one constructor from another in java [duplicate]

Question

This was the question asked in interview. Can we call one constructor from another if a class has multiple constructors in java and when?How can I call I mean syntax?

Answer 1

You can, and the syntax I know is

this(< argument list >); 

You can also call a super class' constructor through

super(< argument list >); 

Both such calls can only be done as the first statement in the constructor (so you can only call one other constructor, and before anything else is done).

Answer 2

Yes, you can do that.

Have a look at the ArrayList implementation for example:

public ArrayList(int initialCapacity) {     super();     if (initialCapacity < 0)         throw new IllegalArgumentException("Illegal Capacity: "+                                            initialCapacity);     this.elementData = new Object[initialCapacity]; }  /**  * Constructs an empty list with an initial capacity of ten.  */ public ArrayList() {     this(10); } 

The second constructor calls the first one with a default capacity of ten.