casting

问题 Here is a very simple case: I am trying to cast an Object type to a primitive like this: Object object = Integer.valueOf(1234); int result1 = int.class.cast(object); //throws ClassCastException: Cannot convert java.lang.integer to int int result2 = (int)object; //works fine This is the source code of cast method of class 'Class' public T cast(Object obj) { if (obj != null && !isInstance(obj)) throw new ClassCastException(cannotCastMsg(obj)); return (T) obj; } private String cannotCastMsg

问题 I want to know why below downcast fails @ run time: case 1: Object y = 10.23; Console.WriteLine(y.GetType()); //System.Double int z = (int)y;// fails @ runtime Console.ReadKey(); case 2: Double y = 10.23; Console.WriteLine(y.GetType());//System.Double int z = (int)y;//success Console.ReadKey(); In both the cases the type of y is System.Double, still why downcst fails in first case? 回答1: In the first example; unboxing (what you show) is different to downcasting or conversion; it is perhaps

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How do the equality (== double equals) and identity (=== triple equals) comparison operators differ? Why this var_dump(0 == "string"); outputs this bool(true) Isn't the context of == operator supposed to convert 0 into FALSE and "string" into TRUE according to this set of rules? 回答1: var_dump(0 == "string"); is doing a numeric (integer) comparison 0 is an integer, so "string" is converted to an integer to do the

问题 I have got a similar problem like Cheva had in his Question: How to cast System.Object[*] to System.Object[] I use an external library (Reuters EIKON API) via the COM interop functionality. After submitting a request, the object gets updated and its data member gets updated. The Object catalogue shows this for the Data member: public virtual dynamic Data { get; } In the debug mode, I can see, that after submitting the request, DataStatus changes to dataset_full and the Data member is actually

问题 How to convert __int64 to long in Windows (MSVC8 & MSVC6)? Will a normal typecasting work? Also, how about converting long to __int64? If the long is a negative value, will it work? Note - I am talking of a scenario in which the __int64 variable will always contain a value which will not be more than 32 bits long. 回答1: 1. Convert long to __int64 Acorrding to MSDN on the __int64 keyword: The _ _int64 keyword declares a new type, a 64-bit (8-byte) integer. As with the int, short, and long types

问题 How to convert __int64 to long in Windows (MSVC8 & MSVC6)? Will a normal typecasting work? Also, how about converting long to __int64? If the long is a negative value, will it work? Note - I am talking of a scenario in which the __int64 variable will always contain a value which will not be more than 32 bits long. 回答1: 1. Convert long to __int64 Acorrding to MSDN on the __int64 keyword: The _ _int64 keyword declares a new type, a 64-bit (8-byte) integer. As with the int, short, and long types

问题 The following code: echo (int) "2e2"; echo (int) 2e2; echo (float) "2e2"; outputs 2 200 200 .. and i have no idea why. Thanks. 回答1: "2e2" is scientific notation, meaning 2*10 2 == 200. In your first example, parsing the string as an int reads only digits up to the first non-digit (so it ignores the e ). The PHP parser treats 2e2 as a float literal with value 200.0 and this gives 200 when cast to a int. Parsing the string as a float understands the notation and gives the expected result of 200

问题 I have a web application (WAR file) which uses jersey jars.Now when i am trying to deploy this i am getting class cast exception(Some bootstrap servlet uses jersey)..On analysis i found that weblogic itself have jersey jars in common\modules..and my web app have different version of jersey jars. Now if i delete the common/modules jersey jar then my web app got deployed.I want to know how can i make my web app to use its own version of jersey jars so that it gets deployed without deleting

问题 I have a web application (WAR file) which uses jersey jars.Now when i am trying to deploy this i am getting class cast exception(Some bootstrap servlet uses jersey)..On analysis i found that weblogic itself have jersey jars in common\modules..and my web app have different version of jersey jars. Now if i delete the common/modules jersey jar then my web app got deployed.I want to know how can i make my web app to use its own version of jersey jars so that it gets deployed without deleting

问题 Or is it always guaranteed to be positive for all possible Chars? 回答1: It's guaranteed to be non-negative. char is an unsigned 16-bit value. From section 4.1.5 of the C# 4 spec: The char type represents unsigned 16-bit integers with values between 0 and 65535. The set of possible values for the char type corresponds to the Unicode character set. Although char has the same representation as ushort , not all operations permitted on one type are permitted on the other. 回答2: Since the range of