Eclipse “cannot be resolved to a type” error

引言： 

    eclipse新導入的項目經常可以看到“XX cannot be resolved to a type”的報錯信息。本文將做以簡單總結。 

正文： 

    （1）jdk不匹配（或不存在） 

    項目指定的jdk爲“jdk1.6.0_18”，而當前eclipse使用的是“jdk1.6.0_22”。需要在BuildPath | Libraries，中做簡單調整。 

    （2）jar包缺失或衝突 

    當找不到“XX”所在的jar包時，會報這個錯。解決只需要找到（ctrl+點擊，可能能看到jar包名稱）對應jar包導入項目即可。 

    另外，出現相同的XX時也會報此錯。可能需要調包、解包、選刪。 

    （3）eclipse查找項目類型策略所致 

    eclipse下，上述兩條都對比過了，沒有任何問題，可偏偏還報這錯。這時，需要操作一下 Project | Clean... ，問題即可解決。原因是，機制所致。因爲某些特殊原因，eclipse沒能自動編譯源代碼到build/classes（或其他classes目錄），導致類型查找不到。 

Based on the comments here, I started checking how I could make sure that my Ant build 

wouldn’t interfere with my Eclipse build.

I found an option in Eclipse that clears up the problem (and is possibly more efficient than

 changing the 2 build system’s output folders).

Windows–>Preferences–>Java–>Compiler–>Building–>Output folder–>

”Rebuild class files modified by others”. This exists in Eclipse 3.5; I’m not sure about earlier versions.

Checking this seems to have fixed my problems

轉自：http://www.cnblogs.com/xuxm2007/archive/2011/10/20/2219104.html