terminology

问题 What's the definition of a Shim? 回答1: From Wikipedia: In computer programming, a shim is a small library that transparently intercepts an API, changing the parameters passed, handling the operation itself, or redirecting the operation elsewhere. Shims typically come about when the behaviour of an API changes, thereby causing compatibility issues for older applications that still rely on the older functionality. In these cases, the older API can still be supported by a thin compatibility layer

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 3 years ago . Can you post a short example of real, overdone spaghetti code, possibly saying what it does? Can you show me a little debugger's nightmare? I don't mean IOCCC code, that is science fiction. I mean real life examples that happened to you... Update The focus has changed from "post

问题 What is meant by ‘value semantics’, and what is meant by ‘implicit pointer semantics’? 回答1: Java is using implicit pointer semantics for Object types and value semantics for primitives. Value semantics means that you deal directly with values and that you pass copies around. The point here is that when you have a value, you can trust it won't change behind your back. With pointer semantics, you don't have a value, you have an 'address'. Someone else could alter what is there, you can't know.

问题 In some texts about XML, the terms tag and element seem to be used interchangeably. Do they mean the same thing, or are do these terms represent different things? 回答1: Tags mark the start and end of an element. <foo> — start tag </foo> — end tag <foo></foo> — element See the specification: Each XML document contains one or more elements, the boundaries of which are either delimited by start-tags and end-tags, or, for empty elements, by an empty-element tag. See also section 5 of NOT the comp

问题 What's the difference in the outcome between call by reference and copy/restore? Background: I'm currently studying distributed systems. Concerning the passing of reference parameters for remote procedure calls, the book states that: "the call by reference has been replaced by copy/restore. Although this is not always identical, it is good enough". I understand how call by reference and copy/restore work in principle, but I fail to see where a difference in the result may be? 回答1: Examples

问题 What does the term Plain Old Java Object (POJO) mean? I couldn't find anything explanatory enough. POJO's Wikipedia page says that POJO is an ordinary Java Object and not a special object. Now, what makes or what doesn't make and object special in Java? The above page also says that a POJO should not have to extend prespecified classes, implement prespecified Interfaces or contain prespecified Annotations. Does that also mean that POJOs are not allowed to implement interfaces like

问题 I know that Hibernate implements ORM (Object Relational Mapping), what type of mapping does JDBC implement? Does it implement DAO? I don't totally understand how/if DAO is related to JDBC...? 回答1: DAO isn't a mapping. DAO stands for Data Access Object. It look something like this: public interface UserDAO { public User find(Long id) throws DAOException; public void save(User user) throws DAOException; public void delete(User user) throws DAOException; // ... } For DAO, JDBC is just an

问题 My neighbor is taking "Intro to Java", and asked me to help explain a few of the first-day concepts. I realized that since I do this everyday, I don't have the beginner's mind, and it's hard to relate some of this stuff from scratch. The one that's actually not trivial for me to explain is "what the heck is a class?" Best I have so far: A variable holds some kind of data; one variable might be a first name, another variable might be your weight in pounds. A method is a function, it does stuff

问题 The following higher order predicate succeeds if all pairs of the list's elements are true for a given relation. Is there a common or better, more intention revealing name for this relation? My original motivation for this name was that in clpfd, there is often a constraint all_different/1 which is described as being true, iff the elements are pairwise different . In fact, rather preferred to say the elements are all different, but I have been frequently corrected (by fellow Prolog

问题 This question already has answers here : What are the double colons (::) in R? (2 answers) Closed 2 years ago . I'm wondering how the functions of the :: and ::: operators differ in R. However, I can't figure out what these operators are called and so a google or SO search has not proven helpful. I also get an error when I try ?:: in R. So... What are the :: and ::: operators called? How do :: and ::: differ? (i.e., what exactly does each do)? 回答1: It turns out there is a unique way to access