casting

问题 public K[] toArray() { K[] result = (K[])new Object[this.size()]; int index = 0; for(K k : this) result[index++] = k; return result; } This code does not seem to work, it will throw out an exception: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to ... Could someone tell me how I can create an array with a generic type? Thanks. 回答1: You can't: you must pass the class as an argument: public <K> K[] toArray(Class<K> clazz) { K[] result = (K[])Array.newInstance(clazz,this.size

问题 public K[] toArray() { K[] result = (K[])new Object[this.size()]; int index = 0; for(K k : this) result[index++] = k; return result; } This code does not seem to work, it will throw out an exception: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to ... Could someone tell me how I can create an array with a generic type? Thanks. 回答1: You can't: you must pass the class as an argument: public <K> K[] toArray(Class<K> clazz) { K[] result = (K[])Array.newInstance(clazz,this.size

问题 public K[] toArray() { K[] result = (K[])new Object[this.size()]; int index = 0; for(K k : this) result[index++] = k; return result; } This code does not seem to work, it will throw out an exception: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to ... Could someone tell me how I can create an array with a generic type? Thanks. 回答1: You can't: you must pass the class as an argument: public <K> K[] toArray(Class<K> clazz) { K[] result = (K[])Array.newInstance(clazz,this.size

问题 I've got a few columns that have values either in fractional strings (i.e. 6 11/32) or as decimals (1.5). Is there a CAST or CONVERT call that can convert these to consistently be decimals? The error: Msg 8114, Level 16, State 5, Line 1 Error converting data type varchar to numeric. Can I avoid doing any kind of parsing? Thanks! P.S. I'm working in SQL Server Management Studio 2012 . 回答1: CREATE FUNCTION ufn_ConvertToNumber(@STR VARCHAR(50)) RETURNS decimal(18,10) AS BEGIN DECLARE @L VARCHAR

问题 I would like to display a CAST datetime in an SQL table using the RFC822 format (ex: Fri, 19 Nov 2010 13:43:39 ) from the following SELECT (part of a larger statement found here) *_snip_* ,(Select Cast(Cast(FieldValue as nvarchar(max)) as DateTime) from dbo.UserDefinedData where UserDefinedFieldId = 298 and UserDefinedRowId = item.UserDefinedRowId) as [pubDate] The bit of SQL below will retrieve the current date in the desired format. How can I integrate it into the above statement (or is

问题 I'm using PostgreSQL 9.2 . This blog entry by Grace Batumbya provides a cast from bytea to oid . create or replace function blob_write(lbytea bytea) returns oid volatile language plpgsql as $f$ declare loid oid; lfd integer; lsize integer; begin if(lbytea is null) then return null; end if; loid := lo_create(0); lfd := lo_open(loid,131072); lsize := lowrite(lfd,lbytea); perform lo_close(lfd); return loid; end; $f$; CREATE CAST (bytea AS oid) WITH FUNCTION blob_write(bytea) AS ASSIGNMENT;

问题 How can store an Int64 number in VB6, to work with Win32 functions? Is there a way to define a type like Int64 in .net? And simply evaluate the number. 回答1: I think many of VB6 programmers need something like this, Because some of the Win32 API's use _int64 as their parameters. I wrote a function to cast a currency into an API compatible structure. Put these codes in a module file. Private Declare Sub CopyMemory lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal

问题 How can store an Int64 number in VB6, to work with Win32 functions? Is there a way to define a type like Int64 in .net? And simply evaluate the number. 回答1: I think many of VB6 programmers need something like this, Because some of the Win32 API's use _int64 as their parameters. I wrote a function to cast a currency into an API compatible structure. Put these codes in a module file. Private Declare Sub CopyMemory lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal

问题 How can store an Int64 number in VB6, to work with Win32 functions? Is there a way to define a type like Int64 in .net? And simply evaluate the number. 回答1: I think many of VB6 programmers need something like this, Because some of the Win32 API's use _int64 as their parameters. I wrote a function to cast a currency into an API compatible structure. Put these codes in a module file. Private Declare Sub CopyMemory lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal

问题 Let's say I have these types: struct A { int a; }; struct B { int b; }; struct C : public A, public B { int c; }; A C* pointer can be cast to A* pointer without adjusting the actual address at all. But when C* is cast to B* , the value must change. I'd like to ensure that two related types I have can be cast to each other without a change in address (i.e. that there is no multiple inheritance, or that the base class is the first base of the derived class). This could be checked at run-time, e