解决com.sun.tools.javac.Main is not on the classpath的问题

在重装了JDk之后，有可能会使Eclipse在编译工程的时候出现如下错误：

com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:/Program Files/Java/jre1.5.0_11" 

遇到这种情况时直接将C:/Program Files/Java/jdk1.5.0_11/lib中的tools.lib拷贝到C:/Program Files/Java/jre1.5.0_11/lib中即可。