Databases
StackOverflow2013
Postsdbo
POJava reference and new keyword
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POJava reference and new keyword
    primarykey
    data
    text
    <p>I'm writing a simple chessboard while learning Java and come up with the following question:</p> <p>I have abstract class <code>ChessPiece</code> and classes like <code>King</code>, <code>Queen</code>, <code>Rook</code> etc. which all extend <code>ChessPiece</code>.</p> <p>And I have a 2D array of ChessPiece for the chessboard.</p> <pre><code>public ChessPiece myChessBoard[][] = new ChessPiece[8][8]; </code></pre> <p>Then I make my chess pieces like this:</p> <pre><code>ChessPiece aPiece = new Rook(); </code></pre> <p>And put it on myChessBoard so I can find it:</p> <pre><code>myChessBoard[0][0] = aPiece; </code></pre> <p>Same goes for other pieces...</p> <p>My question is when I do this <code>public ChessPiece myChessBoard[][] = new ChessPiece[8][8]; </code> in my first step, I used new keyword and allocated 8*8 = 64 ChessPiece objects right? But I did it again when writing <code>ChessPiece aPiece = new Rook();</code> I feel stuff in myChessBoard such as myChessBoard[0][0] don't need to be allocated since it's just a reference and don't need that much space as a real chess piece like <code>new Rook()</code>. </p> <p>In short I feel I only need to allocate 32 chess pieces with new keyword (32 pieces on a chessboard) instead of 32 + 64 = 96 chess pieces.</p> <p>I might have confused some basic concept in Java, please help.</p> <p>Edit:</p> <p><code>myChessBoard[][] = new ChessPiece[8][8]</code> here I used new keyword to create 64 reference without real object. So new keyword doesn't necessarily create new objects, it can also create new references referring to null, right? </p> <p>that is wrong. "the new keyword in that case is creating a new 2D array Object" thanks to accepted answer.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USArch1tect
    1. USArch1tect
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POJava reference and new keyword
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POJava reference and new keyword
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POJava reference and new keyword
      1. This table or related slice is empty.
      1. VTUpMod
    1. COyou are instantiating the abstract class?
      singulars
      1. POJava reference and new keyword
      1. USuser2837260
    2. CO@user2837260 no, I'm not. The only abstract class is `ChessPiece`
      singulars
      1. POJava reference and new keyword
      1. USArch1tect
    3. CO`new ChessPiece[8][8];` ??
      singulars
      1. POJava reference and new keyword
      1. USuser2837260
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload