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问题 I have the following class, that is mapped by Jackson (simplified version): public class POI { @JsonProperty("name") private String name; } In some cases the server returns "name": null and I would like to then set name to empty Java String. Is there any Jackson annotation or should I just check for the null inside my getter and return empty string if the property is null ? 回答1: You can either set it in the default constructor, or on declaration: public class POI { @JsonProperty("name")

问题 I have a table called Initial_Fees . There is a column in this table called Initial_Consult_Fee where it cannot be more than 30,000 per year. Below is my table. CREATE TABLE `initial_fees` ( `idInitial_Fees` int(11) NOT NULL AUTO_INCREMENT, `idPortfolio` int(11) NOT NULL, `Current_Time_Stamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, `Initial_Gross_Fee` double NOT NULL, `Initial_Consult_Fee` double NOT NULL, `Updated_Date` date NOT NULL, `idTransactions` int(11

问题 Suppose I want to have two variables and have them both equal to null . (More realistically, I am thinking about an array that contains a large amount of null s, but the "two variables" scenario is sufficient for the question.) Obviously, I can do this in more than one way. I can do this (method 1): $a = null; $b = $a; By my understanding, the result of this is that there is one zval that is pointed to by two entries in the symbol table: 'a' and 'b' . But alternatively one might do this

问题 I've just come across an interesting scenario on how NULL is handled in T-SQL (and possibly other forms of SQL). The issue is pretty well described and answered by this question and I've illustrated the issue below; -- SET ANSI_NULLS ON -- Toggle this between ON/OFF to see how it changes behaviour DECLARE @VAR1 DATETIME DECLARE @VAR2 DATETIME SET @VAR1 = (SELECT CURRENT_TIMESTAMP) SET @VAR2 = (SELECT NULL) -- This will return 1 when ansi_nulls is off and nothing when ansi_nulls is on SELECT 1

问题 I find myself using a common run-time type identification pattern, especially when writing code that handles controls of varying types. Here is the pattern: if (ctrl is ControlTypeEtc) (ctrl as ControlTypeEtc).SomeMethod(); I do this to avoid having to do a NULL check in case the as operator returns NULL. Is there a way to streamline this to a single operation? 回答1: No way to do this in a single operation. However, using as and checking for null is cheaper as there is only one case instead of

问题 Options A: if (NULL == pSomethingColumn) // Yes, we use Yoda conditions if (NULL != pSomethingColumn) Or if (pSomethingColumn) if (!pSomethingColumn) I am looking for references explaining the reasoning as well. I have heard some people say that technically NULL does not have to be defined as 0 , but come on! if that was the case, then the sucker (our app) would crash in -2147483648 different ways. So, if NULL != 0 , then we will have big problems. Please help me settle a pointless syntax

问题 The problem I have is that CreateInstance returns null. Here is the code: if(spattmono[0] != null) { if((SpecialAttack) System.Activator.CreateInstance( spattmono[0].GetClass()) == null) { Debug.Log("DUMB ACTIVATOR!!!"); } //combo.SetSpecialAttack(spattack); } Attack and SpecialAttack are both classes that store basic information, and inherit from UnityEngine.Object . Attmono and spattmono are both MonoScript arrays, attmono being able to hold 16 and spattmono being able to hold 4. They get

问题 if not (i_ReLaunch = 1 and (dt_enddate is not null)) How this epression will be evaluated in Oracle 10g when the input value of the i_ReLaunch = null and the value of the dt_enddate is not null it is entering the loop. According to the rules in normal c# and all it should not enter the loop as it will be as follows with the values. If( not(false and (true)) = if not( false) =if( true) which implies it should enters the loop But it is not happening Can someone let me know if i am wrong at any

问题 This question already has answers here : Why doesn't delete set the pointer to NULL? (12 answers) Why doesn't free(p) set p to NULL? (9 answers) Closed 2 years ago . I have small piece of code: #include <iostream> using namespace std; int main() { int *p = new int(10); if(p != NULL) { cout<<"Deleted dynamic allocated memory"<<endl; delete p; } if(p == NULL) { cout<<"NULL"<<endl; } else { cout<<"Not NULL"<<endl; } return 0; } After deleting dynamic allocated memory using delete operator, Why

问题 I am looking for the best way to check if a Com Object exists. Here is the code that I have; I'd like to improve the last line: $ie = New-Object -ComObject InternetExplorer.Application $ie.Navigate("http://www.stackoverflow.com") $ie.Visible = $true $ie -ne $null #Are there better options? 回答1: I would stick with the $null check since any value other than '' (empty string), 0 , $false and $null will pass the check: if ($ie) {...} . 回答2: You can also do if ($ie) { # Do Something if $ie is not