Multiple markers at this line - Implicit super constructor Object() is undefined for default constr

Multiple markers at this line
- Implicit super constructor Object() is undefined for default constructor. Must
define an explicit constructor
- The hierarchy of the type FirstController is inconsistent

Implicit super constructor Object() is undefined for default constructor. Must define an explicit constructor
解 决方案：把java的类库加载进去，在工程上右键选择属性->Java Build Path的Libraries->Add Library选择JRE System Library->点击Next->选择Execution environment并选择版本或workspace default jre->点击Finish。