在ecliipse-->preference-->Java--->Debug 设置

Suspend execution:
只保留 suspend for breakpoint.

Hot code replace
保留: show error when hot code replace failed.
          show error when obsolete code remain after replace.
          replace classfiles containing compilation errors.

Communication:
change Debugger timer  to 30000
Launch timer to 200000

The project was not built since its build path is incomplete. The project was not built since its build path is incomplete. Fix the build path then try building this project
The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files

出現以上訊息的原因是因為你裝了多個版本的jre或jdk的關係。本來Eclipse在建立專案時，會自動參照你的jre路徑，但多個版本就沒辦法了。
你只能手動建立…
1. 進入window\preferences\java\Installed JREs
1)按Add
2)輸入JRE Name, 例JDK1.5.0.03
3)JRE home directory, 選擇安裝的路徑
4)按OK
2. 進入Project\properties\Java Bulid Path
1)Add library
2)選JRE System Library後按Next
3)選workplace default JRE後按finish...