what is stub？
小知识点，我google了一下，找了一些认为比较满意的答案贴过来。供君参考。
实际上如果你知道它是 substitute的缩写就可以了
A stub is a small program routine that substitutes for a longer program, possibly to be loaded later or that is located remotely. For example, a program that uses Remote Procedure Calls ( RPC ) is compiled with stubs that substitute for the program that provides a requested procedure. The stub accepts the request and then forwards it (through another program) to the remote procedure. When that procedure has completed its service, it returns the results or other status to the stub which passes it back to the program that made the request.
A routine that doesn't actually do anything other than declare itself and the parameters it accepts. Stubs are used commonly as placeholders for routines that still need to be developed. The stub contains just enough code to allow it to be compiled and linked with the rest of the program.
A stub is a controllable replacement for an existing dependency (or collaborator) in the system. By using a stub, you can test your code without dealing with the dependency directly.
这里的dependency可能是指，函数或者类等等：
Anything that the code uses. It might help to understand if you re-read and replace "dependency" with "class" or "function" or whatever (depends on your background).
A stub, in this context, means a mock implementation.
That is, a simple, fake implementation that conforms to the interface and is to be used for testing.
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更加专业一点儿的解释：
A stub, in the context of distributed computing, is a piece of code that is used to convert parameters during a remote procedure call (RPC). An RPC allows a client computer to remotely call procedures on a server computer. The parameters used in a function call have to be converted because the client and server computers use different address spaces. Stubs perform this conversion so that the remote server computer perceives the RPC as a local function call.
翻译做中转或者替代，多为机器自动产生。
Stub libraries are generally installed on the client and server. Client stubs convert parameters used in function calls and reconvert the result obtained from the server after function execution. Server stubs, on the other hand, reconvert parameters passed by clients and convert results back after function execution.
Stubs are generated either manually or automatically. In a manual generation, a remote procedure call implementer provides translation functions, from which a user constructs stubs. They handle complex parameter types. Automatic stub generation is commonly used to generate stubs. They use integration description language to define client and server interfaces.
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更经典的总结：
https://en.wikipedia.org/wiki/Method_stub
A method stub or simply stub in software development is a piece of code used to stand in for some other programming functionality. A stub may simulate the behavior of existing code (such as a procedure on a remote machine) or be a temporary substitute for yet-to-be-developed code. Stubs are therefore most useful in porting, distributed computing as well as general software development and testing.
An example of a stub in pseudocode might be as follows:
BEGIN Temperature = ThermometerRead(Outside) IF Temperature > 40 THEN PRINT "It's HOT!" END IF END BEGIN ThermometerRead(Source insideOrOutside) RETURN 28 END ThermometerRead
The above pseudocode utilises the function ThermometerRead, which returns a temperature. While ThermometerRead would be intended to read some hardware device, this function currently does not contain the necessary code. So ThermometerRead does not, in essence, simulate any process, yet it does return a legal value, allowing the main program to be at least partially tested. Also note that although it accepts the parameter of type Source, which determines whether inside or outside temperature is needed, it does not use the actual value passed (argument insideOrOutside) by the caller in its logic.
A stub [1] is a routine that doesn't actually do anything other than declaring itself and the parameters it accepts and returning something that is usually the values expected in one of the "happy scenarios" for the caller. Stubs are used commonly as placeholders for implementation of a known interface, where the interface is finalized/known but the implementation is not yet known/finalized. The stub contains just enough code to allow it to be compiled and linked with the rest of the program. In RMI nomenclature, a stub communicates on the server-side with a skeleton.[2]
Android Binder这一块儿也有个Stub，如果你理解Binder的话，那么stub就很好理解了。
更通俗的理解是： “默认生成，有待实现”
就这样，不贪多。
merlin
2015/10/22