Does anyone knows how to fix this nullpointerexception?
https://haste.nycode.de/gipicaxune.avrasm
Silvan
The world you are trying to load with your code (Bukkit.getWorld("myWorld");) in class InventoryListener in line 55.
Before you handle optional information you should check if it exist.
Example:
if(Bukkit.getWorld("myWorld") == null) {
return;
}
Bukkit.getWorld("myWorld").//do something
Related
I have userDto, contains programs, which contains actual field. Actual program can be only one. I need to get it. Than, I run this:
userDto.programs.sortedBy { it.created }.findLast { it.actual }?
Okay, but I want to foresee case, when findLast returns null, & throw exception. Please, advice, how to do it?
UPD:
ProgramType.valueOf(userDto.programs
.sortedBy { it.created }
.findLast { it.actual }
//check here
!!.programType!!).percentage
You are pretty close actually :)! What you could do is:
userDto.programs.sortedBy { it.created }.findLast { it.actual } ?: throw RuntimeException()
Or if you're trying to actually avoid throwing an error(couldn't really tell with the way question is asked), you could just do an error check like this:
userDto.programs.sortedBy { it.created }.findLast { it.actual }?.let{
//rest of your code goes here
}
Hope this helps, cheers!
EDIT: The issue was with the assert as people pointed out below. Thanks for the help!
I have a enum set that i'm trying equate, but for some reason its not working.
Its declared like so:
typedef NS_ENUM(NSUInteger, ExUnitTypes) {
kuNilWorkUnit,
kuDistanceInMeters,
//end
kuUndefined
};
And i'm using it here:
+(NSString*) ExUnitDescription: (ExUnitTypes) exUnit
{
if (exUnit == kuNilWorkUnit)
{
assert("error with units");
}
///.... more stuff
}
Xcode isnt triggering my assert. EDIT: the assert is just for testing. i've used NSLog as well. The conditional isn't evaluating to true even though the value is clearly kuNilWorkUnit.
Does anyone have any suggestions or ideas of what i'm doing wrong?
You want to do this:
+(NSString*) ExUnitDescription: (ExUnitTypes) exUnit
{
assert(exUnit != kuNilWorkUnit);
///.... more stuff
}
This is because, assert only stops execution if the expression you pass to it is false. Since a string literal is always non-zero, it will never stop execution.
Now, since you are using Objective C and it also looks like you want to have a message associated with your assert, NSAssert would be preferable.
+(NSString*) ExUnitDescription: (ExUnitTypes) exUnit
{
NSAssert(exUnit != kuNilWorkUnit, #"error with units");
///.... more stuff
}
Unit testing and xdebug usage aside, I wish to have a way to throw some browser message is a value is not expected to be present.
Let's say: $className = 45;
If we have:
public function setMainClass($className) {
if (is_string($className)) {
$this->_mainClass = $className;
} else {
echo Yii::trace(CVarDumper::dumpAsString($className),'vardump');
}
}
We will get this output to the browser on development stage.
It's great.
I'm not sure however, if this is a proper way of use Yii::trace of if I'm miss using it.
Please advice.
It is not necessary to echo the call Yii::trace() (it returns void so the echo does nothing). The other recommendation is that you might consider changing category to resemble a path alias as discussed in the documentation. For example-
} else {
Yii::trace(CVarDumper::dumpAsString($className), 'application.models.MyGreatModel');
}
In the following method, I need to handle if a null gets passed in but I am unsure how. How do I handle this so this method will pass a JUnit test?
public Album(String name) {
if(name==null){
// what do I do here?
}
this.name = name;
this.images = new ArrayList<Image>();
}
And in this method, how do I handle if the index passed in is either negative or greater than the size of the array list it is getting from?
public Image getImage(int index) {
if (index < 0 || index > images.size()) {
// how to handle here?
}
return images.get(index);
}
I've tried various things for both, but these methods keep failing their JUnit tests. Thank you for any input you can give me.
if(name==null){
throw new IllegalArgumentException("name");
}
although personally I don't see anything wrong with throwing NullPointerException directly.
if (index < 0 || index > images.size()) {
throw new ArrayIndexOutOfBounds(index);
}
But you know what? images.get(index) will throw it as well, so don't bother checking it first. Less code to read and test. In fact you already made a mistake. Your precondition will let index equal to images.size(). There should have been index >= images.size().
In below code I want to neutralize the throw and continue the method - Can it be done ?
public class TestChild extends TestParent{
private String s;
public void doit(String arg) throws Exception {
if(arg == null) {
Exception e = new Exception("exception");
throw e;
}
s=arg;
}
}
The net result should be that, in case of the exception triggered (arg == null)
throw e is replaced by Log(e)
s=arg is executed
Thanks
PS : I can 'swallow' the exception or replace it with another exception but in all cases the method does not continue, all my interventions take place when the harm is done (ie the exception has been thrown)
I strongly doubt that general solution exists. But for your particular code and requirements 1 and 2:
privileged public aspect SkipNullBlockAspect {
public pointcut needSkip(TestChild t1, String a1): execution(void TestChild.doit(String))
&& this(t1) && args(a1) ;
void around(TestChild t1, String a1): needSkip(t1, a1){
if(a1==null) //if argument is null - doing hack.
{
a1=""; //alter argument to skip if block.
proceed(t1, a1);
t1.s=null;
a1=null; //restore argument
System.out.println("Little hack.");
}
else
proceed(t1, a1);
}
}
I think that generally what you want makes no sense most cases because if an application throws an exception it has a reason to do so, and that reason almost always includes the intention not to continue with the normal control flow of the method where the exception was thrown due to possible subsequent errors caused by bogus data. For example, what if you could neutralise the throw in your code and the next lines of code would do something like this:
if(arg == null)
throw new Exception("exception");
// We magically neutralise the exception and are here with arg == null
arg.someMethod(); // NullPointerException
double x = 11.0 / Integer.parseInt(arg); // NumberFormatException
anotherMethod(arg); // might throw exception if arg == null
Do you get my point? You take incalculable risks by continuing control flow here, assuming you can at all. Now what are the alternatives?
Let us assume you know exactly that a value of null does not do any harm here. Then why not just catch the exception with an after() throwing advice?
Or if null is harmful and you know about it, why not intercept method execution and overwrite the parameter so as to avoid the exception to begin with?
Speculatively assuming that the method content is a black box to you and you are trying to do some hacky things here, you can use an around() advice and from there call proceed() multiple times with different argument values (e.g. some authentication token or password) until the called method does not throw an exception anymore.
As you see, there are many ways to solve your practical problem depending on what exactly the problem is and what you want to achieve.
Having said all this, now let us return to your initial technical question of not catching, but actually neutralising an exception, i.e. somehow avoiding its being thrown at all. Because the AspectJ language does not contain technical means to do what you want (thank God!), you can look at other tools which can manipulate Java class files in a more low-level fashion. I have never used them productively, but I am pretty sure that you can do what you want using BCEL or Javassist.