Blog from Thorsten Gunkel

2011-12-16

Istanbul 2011

14 Pictures

Istanbul 2011
Folder date 2011-10-27
Istanbul 2011
Relevant links:

Istanbul

10-12-2011 03.01

2011-12-12

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Java java.sql.Date equals

2011-12-10

Sailing in Split

20 Pictures

Split 2011
Folder date 2011-09-30
Sailing in Split 2011
Relevant links:

Split

10-12-2011 03.01

2011-12-08

Java: Foo.class.getName() does no longer initialize static blocks

Imaging you have the following to Java class with a static attribute

public class ClassWithStaticVariable
{
protected static int myNumber=0;

public static int getMyNumber()
{
return myNumber;
}

}

No you extend this class and want to initialize the static attribute of
your father in a static block (for whatever reason)

public class ClassWithStaticBlock extends ClassWithStaticVariable
{
static
{
myNumber=42;
}
public static void init() { };
}

It is obvious that if you just read the static variable of the father's
class the static init block never gets executed:

System.out.println(ClassWithStaticVariable.getMyNumber());
0

But how do you ensure it is executed? It seems to be a common practice
to execute the getName() method on the class attribute

ClassWithStaticBlock.class.getName();
System.out.println(ClassWithStaticVariable.getMyNumber());

Sadly, this stopped working after Java 1.4:
Result / Java Environment
42 / Java Vendor: Sun Microsystems Inc. Java version: 1.4.2_19 OS: x86 Windows Vista 6.1
0 / Java Vendor: Sun Microsystems Inc. Java version: 1.6.0_27 OS: x86 Windows 7 6.1
0 / Java Vendor: Oracle Corporation Java version: 1.7.0 OS: x86 Windows 7 6.1
So you better not trust static init blocks to be executed if you call
class.getName(). A reliable alternative might be to add an empty static
method to the class and call that method:

ClassWithStaticBlock.init();

This will trigger the static init block plus you can even add code to
the init method. Remember however, that this code maybe called more than
once, while your static init block normally is only executed once.

10-12-2011 13.01

2011-12-03

Java VisualVm has stopped working

With Windows 7 Java VisualVm stopped working:

Problem signature:
Problem Event Name: APPCRASH
Application Name: jvisualvm.exe
Application Version: 7.0.0.0
Application Timestamp: 4d8c6dcf
Fault Module Name: msvcrt.dll
Fault Module Version: 7.0.7600.16385
Fault Module Timestamp: 4a5bda6f
Exception Code: c0000005
Exception Offset: 00018dbd
OS Version: 6.1.7601.2.1.0.256.4
Locale ID: 1031
Additional Information 1: 0a9e
Additional Information 2: 0a9e372d3b4ad19135b953a78882e789
Additional Information 3: 0a9e
Additional Information 4: 0a9e372d3b4ad19135b953a78882e789
Read our privacy statement online:
http://go.microsoft.com/fwlink/?linkid=104288&clcid=0x0409
If the online privacy statement is not available, please read our privacy statement offline:
C:\Windows\system32\en-US\erofflps.txt

Solution: Check if the following regkey exists and points to a valid directory:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
"AppData"="C:\\Users\\Foo\\AppData"

03-12-2011 15.05