Browse questions answered by Jon Skeet

Warning does not implement the 'collection' pattern

I am making collection, implementing IEnumerable explicitly and trying to iterate it from within: public class MyCollection<T> : IEnumerable<T>, IEnumerable { ...

The warning exists because the C# compiler can handle foreach in a number of different ways. One of those ways is to find a GetEnumerator method with a suitable return type. That's checked before the compiler checks whether or not the type... more 8/15/2017 12:43:41 PM

Struct extension methods

With code: someVector.FixRounding(); //round vector's values to integers if the difference is 1 epsilon float x = someVector.x; //still getting old value public static void...

This declaration: public static void FixRounding(this Vector3 v) ... means v is being passed by value, and it's a struct, assuming the documentation is correct. Therefore any changes you make to it won't be visible to the caller. You... more 8/14/2017 5:54:23 PM

Java PrintWriter File Overwrite

I want to write into a file using UTF-16 so I use PrintWriter(file,"UTF-16"), but then it deletes everything in the file, I could use FileWriter(file,true), but then it wouldn't...

Use OutputStreamWriter with a UTF-16 charset, wrapping a FileOutputStream opened with append=true. Alternatives, use Files.newBufferedWriter: try (Writer writer = Files.newBufferedWriter( Paths.of("filename.txt"), ... more 8/14/2017 3:26:27 PM

Using a generic (X) delegate in a generic (Y) method where Y extends some base class. Cannot convert to base class

public abstract class SomeBaseClass {} public class SomeSpecificClass: SomeBaseClass { public int propertyA; public string propertyB; } public delegate void...

Basically, you can't do this because it's not safe. Suppose we have a concrete class derived from SomeBaseClass: public class SomeOtherSpecificClass {} Suppose we change your MethodB to: void MethodB(Callback<SomeBaseClass>... more 8/14/2017 11:10:19 AM

java jsp if statement

Following code gives me a big headache. Why does my if ignore rs.next() == true? System.out.println(rs.next()); if (rs.next() == true) { ...

What am I doing here wrong? You're calling next() twice. The first call returns true, but presumably the second returns false - which makes sense, if your query only returns a single result. If you really want to print the value out... more 8/13/2017 5:37:41 PM

Unchecked assignment: 'anonymous java.util.Iterator' to 'java.util.Iterator<java.lang.Integer>'

I have a class like this public class Symbol implements Iterable<Integer> { private int n = 123; public Iterator<Integer> iterator() { return new...

All you've got to do is change your anonymous class to use Iterator<Integer> instead of the raw type: return new Iterator<Integer>() { // Code here as before }; Imagine it had been written like this: public... more 8/13/2017 2:53:54 PM

How to transfer a file from Google Cloud Storage to Compute Engine instance using gcloud terminal?

I would like to verify my website in Google Search Console by uploading a file to my website - example.com which is hosted on Google Cloud Compute Engine (Wordpress site deployed...

I don't know if there's a way of doing it in a single step, but it looks like it should be easy to do in two steps: $ gsutil cp gs://example/123googlesearchconsoleexample.html . $ gcloud compute copy-files... more 8/13/2017 2:01:36 PM

Why compiler and run time assuming the string return type as dynamic?

In C# 5 and VS 2017, I have, var json = JsonConvert.SerializeObject(items); // why json is dynamic here Clearly, SerializeObject returns string then why json is dynamic type...

Clearly, SerializeObject returns string then why json is dynamic type instead of string. Almost every operation involving a dynamic value is considered to be dynamic in turn. This includes method calls and most operators. The only... more 8/13/2017 1:45:06 PM

Overloading a class containing an explicit constructor with a call to super ( )

It appears that if a programmer supplied constructor, with a call to super ( ) is used, no other constructor can be invoked in that class ( i.e. it can't be overloaded)....

no other constructor can be invoked in that class ( i.e. it can't be overloaded). That's not true at all. The problem with your Two(int t, int y) constructor is that it doesn't chain to any constructor explicitly, meaning that there's... more 8/12/2017 1:12:34 PM

Why do I need to transform variable into final array inside @Override[inner class] method?

I'm using following code : public void addConditions(){ final String arriveHourse, departHourse, arriveMinutes, departMinutes; TimePickerDialog.OnTimeSetListener...

departHourse is a final variable. It has to be, in order to be used within the anonymous inner class. That means you can't assign a new value to it in the anonymous inner class. One way around that is to create a single-element array... more 8/12/2017 8:37:30 AM