条件Java编译 [英] Conditional Java compilation

问题描述

我是一个长期的C ++程序员，是Java的新手。我正在Eclipse中开发一个Java Blackberry项目。问题 - 有没有办法在项目中引入不同的配置集，然后根据这些编译稍微不同的代码？

在Visual Studio中，我们有项目配置和#ifdef ;我知道Java中没有#ifdef，但也可能是文件级别的一些？

解决方案

您可以设置'final'如果要编译器来优化编译的字节码。

  ... 
 public static final boolean myFinalVar =假; 
 ... 
 if（myFinalVar）{
 do something .... 
 .... 
} 
  

如果代码编译时'myFinalVar'为false，那么做某事....将被错过编译的类。如果你有不止一个条件 - 可以把它们整理一下：把它们全部转移到另一个类（比如'Config.myFinalVar'），然后这些条件都可以保存在一个整齐的位置。

这种机制在'Hardcore Java'。

[实际上我认为这是与前面发布的穷人的ifdef相同的机制。]

I'm a longtime C++ programmer, new to Java. I'm developing a Java Blackberry project in Eclipse. Question - is there a way to introduce different configuration sets within the project and then compile slightly different code based on those?

In Visual Studio, we have project configurations and #ifdef; I know there's no #ifdef in Java, but maybe something on file level?

解决方案

You can set up 'final' fields and ifs to get the compiler to optimize the compiled byte-codes.

...
public static final boolean myFinalVar=false;
...
if (myFinalVar) { 
 do something ....
 ....
}

If 'myFinalVar' is false when the code is compiled the 'do something....' bit will be missed out of the compiled class. If you have more than one condition - this can be tidied up a bit: shift them all to another class (say 'Config.myFinalVar') and then the conditions can all be kept in one neat place.

This mechanism is described in 'Hardcore Java'.

[Actually I think this is the same mechanism as the "poor man's ifdef" posted earlier.]

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