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Java

Md shujaul Haque
Md shujaul Haque
839 Points
Posted by Md shujaul Haque
Md shujaul Haque
839 Points

Constructor 

class SongBook{

  private List<Song> mSongs;

  public SongBook(){
    mSongs = new ArrayList<Song>();
  }

  public void addSong(Song song){
    mSongs.add(song);
  }

  public int getSongCount(){
    return mSongs.size();}
  }

why we use constructor for this class and how its work here and benefit of using it here please explain

[MOD - edited code block - srh]

1 Answer

markmneimneh
markmneimneh
14,132 Points
markmneimneh
markmneimneh
14,132 Points

Hello

regarding your question:

why we use a constructor for this class and how its work here and benefit of using it here please explain

 public SongBook(){
    mSongs = new ArrayList<Song>();
  }


This is the no argument constructor ...  and generally speaking, regardless of the language (Java, C#, C++ ...  it get created for you whether or not you explicitly add it to the code.  

Therefore, you basically get this for free:

 public SongBook(){
  }
No need to add constructor in your java class. Compiler will provide a default no- arg constructor. If you add a constructor, then this default constructor will not be added. If you dont define constructors in java you get one automatically as simple as that.


now since this constructor is called when instantiating an object. as in :

SongBook mySongBook = new SongBook();

why not make use of the default constructor to start a new collection?

and this is what this code is doing when the SongBook mySongBook = new SongBook(); line is executed.

 public SongBook(){
    mSongs = new ArrayList<Song>();
  }
Md shujaul Haque
Md shujaul Haque
839 Points
Md shujaul Haque
Md shujaul Haque
839 Points

thanks a lot its helpful information