java:No enclosing instance of type Classname is accessible. Must qualify the allocation

java编译错误:

No enclosing instance of type Classname is accessible. Must qualify the allocation with an enclosing instance of type Classname(e.g. x.new A() where x is an instance of Classname).

原因：

成员内部类创建之前，必须先创建外部类。

形如：

public class outclass{

public class innerclass{

}

}

想要使用类innerclass，必须先创建外部类。

方法：

outclass out=new outclass();

out.innerclass inner=out.new innerclass();