可以标准的Sun javac做增量编译吗？ [英] Can standard Sun javac do incremental compiling?

问题描述

最近我开始使用Eclipse的java编译器，因为它比标准的javac快得多。我被告知，它更快，因为它执行增量编译。但是我仍然不清楚这一点，因为我找不到关于eclispse和sun的编译器增量功能的权威文件。 Sun的编译器是否总是编译每个源文件，而Eclipse的编译器只编译已更改的文件和受这种更改影响的文件？

编辑：我没有使用Eclipse自动构建功能，而是设置

  -Dbuild.compiler = org.eclipse.jdt.core.JDTCompilerAdapter $ b $对于我的蚂蚁构建，b  

解决方案

这是真的，Sun的编译器总是编译每个源文件，Eclipse的编译器只编译更改的文件那些受这种变化影响的那些？

我相信你是两个都是正确的。

您当然可以强制Eclipse重新编译所有内容。

但方程式的其他部分是Java构建工具（如Ant和Maven）只能编译已经更改的类，以及依赖类的树。

编辑

在Ant中，增量编译可以通过两种方式完成：

• 默认情况下， < javac> 任务将时间戳 .java 和相应的 .class 文件，只告诉Java编译器恢复（.java）文件比其对应的目标（.class）文件更新，或者根本没有目标文件。




• < depend> task / a>还考虑了类之间的依赖关系，它通过阅读和分析嵌入在 .class 文件中的依赖信息来确定。确定哪个 .class 文件已过期，< depend> 任务将删除它们，以便以下< javac> 任务将重新编译它们。但是，这并不完全是愚蠢的。例如，对源代码的大量更改可能导致< depend> 任务可能是分析过时的依赖关系。在 .class 文件格式中，某些类型的依赖关系（例如静态常量）也不明显。

  
  
  

  了解为什么Ant < depend> 不是傻瓜的，请阅读文档。

Recently I started to use Eclipse's java compiler, because it is significantly faster than standard javac. I was told that it's faster because it performs incremental compiling. But I'm still a bit unsure about this since I can't find any authoritative documentation about both - eclispse's and sun's - compilers "incremental feature". Is it true that Sun's compiler always compiles every source file and Eclipse's compiler compile only changed files and those that are affected by such a change?

Edit: I'm not using Eclipse autobuild feature but instead I'm setting

-Dbuild.compiler=org.eclipse.jdt.core.JDTCompilerAdapter

for my ant builds.

解决方案

Is it true that Sun's compiler always compiles every source file and Eclipse's compiler compile only changed files and those that are affected by such a change?

I believe that you are correct on both counts.

You can of course force Eclipse to recompile everything.

But the other part of the equation is that Java build tools like Ant and Maven are capable of only compiling classes that have changed, and their tree of dependent classes.

EDIT

In Ant, incremental compilation can be done in two ways:

• By default the <javac> task compares the timestamps of .java and corresponding .class files, and only tells the Java compiler to recompile source (.java) files that are newer than their corresponding target (.class) files, or that don't have a target file at all.

• The <depend> task also takes into account dependencies between classes, which it determines by reading and analysing the dependency information embedded in the .class files. Having determined which .class files are out of date, the <depend> task deletes them so a following <javac> task will recompile them. However, this is not entirely fool-proof. For example, extensive changes to the source code can lead to the <depend> task may be analysing stale dependencies. Also certain kinds of dependency (e.g. on static constants) are not apparent in the .class file format.

  To understand why Ant <depend> is not fool-proof, read the "Limitations" section of the documentation.

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