terminology

问题 It is not a statement nor an expression. What is that called then? A directive? 回答1: "declaration" See also JLS 7.5. Import Declaration 7.5.1 Single-Type-Import Declaration 7.5.2 Type-Import-on-Demand Declaration 7.5.3 Single Static Import Declaration 7.5.4 Static-Import-on-Demand Declaration 回答2: It's called a Declaration. 回答3: In the general scope, it is a directive. Within Java, classes have a tight relationship between their declaration and their containing file (known as a compiler unit

问题 B-Tree Definition they use the 'order' term in : According to Knuth's definition, a B-tree of order m is a tree which satisfies the following properties: 1. Every node has at most m children. ... and 'Degree' is defined in Tree terms as: Degree – number of sub trees of a node. so, are they same thing? I cannot feel any difference. 回答1: Degree represents the lower bound on the number of children a node in the B Tree can have (except for the root). i.e the minimum number of children possible.

问题 I read the wiki page about heisenbug, but don't understand this example. Can anyone explain it in detail? One common example of a heisenbug is a bug that appears when the program is compiled with an optimizing compiler, but not when the same program is compiled without optimization (as is often done for the purpose of examining it with a debugger). While debugging, values that an optimized program would normally keep in registers are often pushed to main memory. This may affect, for instance,

问题 I read the wiki page about heisenbug, but don't understand this example. Can anyone explain it in detail? One common example of a heisenbug is a bug that appears when the program is compiled with an optimizing compiler, but not when the same program is compiled without optimization (as is often done for the purpose of examining it with a debugger). While debugging, values that an optimized program would normally keep in registers are often pushed to main memory. This may affect, for instance,

问题 I remember reading somewhere that as.tibble() is an alias for as_data_frame() , but I don't know what exactly an alias is in programming terminology. Is it similar to a wrapper? So I guess my question probably comes down to the difference in possible usages between tbl_df() and as_data_frame() : what are the differences between them, if any? More specifically, given a (non-tibble) data frame df , I often turn it into a tibble by using: df <- tbl_df(df) Wouldn't df <- as_data_frame(df) do the

问题 When people mention that Spring is a lightweight containter compared to other frameworks, do they mean? That it occupies less memory in the system or it does not have the operations like start stop that we have for EJB containers and it doesn't use a special container? What makes Spring a lightweight container? 回答1: Whether it is "lightweight" or "heavyweight", it is all about comparison. We consider Spring to be lightweight when we are comparing to normal J2EE container. It is lightweight in

问题 And who has the authority to decide? Edit: Apparently I haven't succeeded in formulating my question well. I am not asking how Java's argument passing works. I know that what looks like a variable holding an object is actually a variable holding a reference to the object, and that reference is passed by value. There are lots of fine explanations of that mechanism here (in the linked threads and others) and elsewhere. The question is about the technical meaning of the term pass-by-reference.

问题 What does the State Transfer in Representational State Transfer refer to? Found some explanations about this (e.g. here) but I still don't understand. For example in the article it is said The representation places the client application in a state. Why? What does state (as I understand it, something like a session) have to do with a representation of a resource? 回答1: Why? What does state (as I understand it, something like a session) have to do with a representation of a resource? An object

问题 While reading the QTKit Application Programming Guide I came across the term 'headless environments' - what does this mean? Here is the passage: ...including applications with a GUI and tools intended to run in a “headless” environment. For example, you can use the framework to write command-line tools that manipulate QuickTime movie files. 回答1: "Headless" in this context simply means without a graphical display. (i.e.: Console based.) Many servers are "headless" and are administered over SSH

问题 I started web development in LAMP/WAMP and it was logical to me. There is a Web Server program called Apache which does the networking part of setting up a service on port 80 (common port). If the request is regular HTML it serves it using HTTP. And if the request is a PHP resource, there is a mod_php with which the Apache invokes the PHP interpreter to process the file and it gives back HTML which is again transferred as usual HTML. Now the question is what is a Web Framework? I came across