public class Parcel4 {
      private class PContents{
          private int i = 11;
          public int value() { return i; }
      }
      public PContents contents() {
          PContents contents=  new PContents();
          return contents;  
      }  
      public static void main(String[] args) {
          Parcel4 parcel4=new Parcel4();
          PContents contents=parcel4.new PContents();
      }
}
为什么在 contents()方法里面PContents可以直接new出来(PContents contents=  new PContents();),
而在Main()方法里面却要创建外围类的对象，再通过外围类的对象进行new出来
Parcel4 parcel4=new Parcel4();
PContents contents=parcel4.new PContents();