jdk1.6.21在eclipse 3.6下存在冲突的问题，但说的不是很详细，有人问到，那我就再说一下吧。这是这个官方就有说明的，在下载页面很明显的标出了，只是有的同学不是在官方下载的或者太粗心没注意到。我们看官方是怎么说的。   

       The Eclipse 3.3 - 3.6 launchers for Windows had a problem with the Oracle/Sun Java VM version '1.6.0_21-b06'.

UPDATE: Oracle/Sun have released a respin of their JDK/JRE to fix this, so the recommended resolution of this problem is to download and re-install version 1.6.0_21-b07' or higher from (alternative link is ). Make sure you have b07 or higher by running java -version.

Before the fix was released, there were three choices to work around this:

1. switch back to '1.6.0_20' (as of July 19, 2010 it can still be downloaded )
2. Change the commandline for launching or add the following line after "-vmargs" to your file: -XX:MaxPermSize=256m ()
3. For 32-bit Helios, download the fixed and place it into (eclipse_home)/plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.0.v20100503

The Java bug was closed for voting and comments at on the Java BugParade because the change has been reverted; the related Eclipse bug report is open for voting and comments at .     已经说得很明白了，由于1.6.0_21-b06中部分包的名字被Oracle公司修改了，会造成原先的插件内存泄露，故官方也给出了三种解决方案。 （1）把JDK的版本降级到 jdk 1.6.0_20。下载地址： （2）修改文件里的设置，在-vmargs后添加或修改下面这句-XX:MaxPermSize=256m。 （3）对于32位版本的Eclipse3.6，可以下载这个补丁。，并且放置到(eclipse_home)/plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.0.v20100503。 （4）升级jdk1.6.0_21-b06到1.6.0_21-b07或更高。