How do I initialize this 2D array with null in Java? -

-

i have made 2-d array store references objects of children classes of parent class student. 

student[][] = new student [5][4];

now want initialize array null? how do it? trick doing @ once? also, wanted know if possible store references of children class in array of base class in java?

i want initialize values null. also, let's values filled , want overwrite values null. how do that?

by default java initialises reference objects null.


Comments

Post a Comment

Popular posts from this blog

c# - Class in a list -

-
i understand in c# class passed reference. mean when store said class in list stored reference well, or better said c# style "pointer" of sorts? mean list n elements of class not take memory n times size of class n times size of reference class? or thinking wrong? you're right. if create n elements of class t, , class t uses, say, 10 bytes, takes on order of 10*n memory. if store in list<t> , still have 10*n memory objects, plus n times size of c# reference , list overhead. if store same elements in 2 lists, have 10*n objects, plus 2*n references, , 2 times list overhead. they're pointing @ same underlying objects.
Read more

ios - RestKit 0.20 — CoreData: error: Failed to call designated initializer on NSManagedObject class (again) -

-
this error has shown on many times, seems. prominent answer issue seems restkit 0.20 — coredata: error: failed call designated initializer on nsmanagedobject class however, solution posted doesn't work me. let's start beginning: i want upload file server. want parse response make sure uploaded. if not, try again later. model has boolean variable called nsnumber *senttoserver purpose (in coredata, bool saved nsnumber ) . because don't know whether sending going successful, save entity coredata model first before sending via restkit. when post request successful, server returns json string this: {"id":14,"created":true} notice that, of course, id not set on coredata model yet, both id , created new informations model. here's model: @interface recording : nsmanagedobject @property (nonatomic, retain) nsstring * audiofilepath; @property (nonatomic, retain) nsdate * createdat; @property (nonatomic, retain) nsstring * deviceid; @...
Read more

Jdbc Odbc Driver error -

-
i have small problem jdbc.odbc.jdbcodbcdriver . it gives me following error: java.sql.sqlexception: driver not support function the code: saverec.addactionlistener(new actionlistener() { @override public void actionperformed(actionevent e) { saverecclick = 1; if (saverecclick == 1) { try { field2.setenabled(false); field3.setenabled(false); field4.setenabled(false); field5.setenabled(false); field6.setenabled(false); table.setenabled(true); mainframe(); string mydriver = "sun.jdbc.odbc.jdbcodbcdriver"; string myurl = "jdbc:odbc:dlfishhunter"; con = drivermanager.getconnection("jdbc:odbc:dlfishhunter"); stmt = con.createstatement(); string query = " insert data (user, datum, location, kind, size , bait)" + ...
Read more