reflection

Change private static final field using Java reflection

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Assuming no SecurityManager is preventing you from doing this, you can use setAccessible to get around private and resetting the modifier to get rid of final, and actually modify a private static final field. Here’s an example: import java.lang.reflect.*; public class EverythingIsTrue { static void setFinalStatic(Field field, Object newValue) throws Exception { field.setAccessible(true); Field modifiersField … Read more

How to read the value of a private field from a different class in Java?

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In order to access private fields, you need to get them from the class’s declared fields and then make them accessible: Field f = obj.getClass().getDeclaredField(“stuffIWant”); //NoSuchFieldException f.setAccessible(true); Hashtable iWantThis = (Hashtable) f.get(obj); //IllegalAccessException EDIT: as has been commented by aperkins, both accessing the field, setting it as accessible and retrieving the value can throw Exceptions, … Read more

Getting attributes of Enum’s value

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This should do what you need. try { var enumType = typeof(FunkyAttributesEnum); var memberInfos = enumType.GetMember(FunkyAttributesEnum.NameWithoutSpaces1.ToString()); var enumValueMemberInfo = memberInfos.FirstOrDefault(m => m.DeclaringType == enumType); var valueAttributes = enumValueMemberInfo.GetCustomAttributes(typeof(DescriptionAttribute), false); var description = ((DescriptionAttribute)valueAttributes[0]).Description; } catch { return FunkyAttributesEnum.NameWithoutSpaces1.ToString() }

Get generic type of class at runtime

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As others mentioned, it’s only possible via reflection in certain circumstances. If you really need the type, this is the usual (type-safe) workaround pattern: public class GenericClass<T> { private final Class<T> type; public GenericClass(Class<T> type) { this.type = type; } public Class<T> getMyType() { return this.type; } }

Programmatic equivalent of default(Type)

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In case of a value type use Activator.CreateInstance and it should work fine. When using reference type just return null public static object GetDefault(Type type) { if(type.IsValueType) { return Activator.CreateInstance(type); } return null; } In the newer version of .net such as .net standard, type.IsValueType needs to be written as type.GetTypeInfo().IsValueType

Checking if a variable is defined?

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Use the defined? keyword (documentation). It will return a String with the kind of the item, or nil if it doesn’t exist. >> a = 1 => 1 >> defined? a => “local-variable” >> defined? b => nil >> defined? nil => “nil” >> defined? String => “constant” >> defined? 1 => “expression” As skalee … Read more