Top "Null" questions

Cleaner way to do a null check in C#?

Suppose, I have this interface, interface IContact { IAddress address { get; set; } } interface IAddress { string city { get; set; } } class Person : IPerson { …

c# .net-4.0 null .net-4.5

HashMap with Null Key and Null Value

Consider the following Code : import java.util.*; class Employee { String name; public Employee(String nm) { this.name=nm; } } public class …

java collections null hashmap hashcode

Update columns with Null values

I tried updating a table as follows: update userloginstats set logouttime = sysdate where logouttime = null; It didn't update the columns …

sql oracle null sql-update

Uninitialized Object vs Object Initialized to NULL

I'm working in Java. I commonly setup some objects as such: public class Foo { private SomeObject someName; // do stuff public …

java null initialization

Why does String.valueOf(null) throw a NullPointerException?

according to the documentation, the method String.valueOf(Object obj) returns: if the argument is null, then a string equal …

java null nullpointerexception overloading api-design

Conditional NOT NULL case SQL

I am trying to calculate a field and I want it to behave differently depending on if one of the …

sql mysql null mysql-error-1064

How to replace all Null values of a dataframe in Pyspark

I have a data frame in pyspark with more than 300 columns. In these columns there are some columns with values …

dataframe null pyspark

Android Calendar get current day of week as string

i tried to get a string with the name of the actual weekday this way: Calendar c = Calendar.getInstance(); int …

java android calendar null dayofweek

Possible causes of Java VM EXCEPTION_ACCESS_VIOLATION?

When a Java VM crashes with an EXCEPTION_ACCESS_VIOLATION and produces an hs_err_pidXXX.log file, what does …

java null jvm crash swt

Why does 'fopen' return a NULL pointer?

I'm working on a simple file splitter/merger program in the C programming language. The problem is, for some reason …

c null fopen fwrite