java - 不允许在main方法中声明

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//这是一个小代码，用于研究集合的工作原理，但是当我在main方法中创建Mountain对象时，会出现错误。最后进一步解释。

import java. util. * ;
    public class sortMountains {
     class Mountain {
               String name;
               int height;
               Mountain(String n, int h) {
                 name      = n;

                 height = h;
               }
               public String toString( ) {
                 return name +  + height;
               }
            }
    List<Mountain> mtn  = new ArrayList<Mountain> ();
      class NameCompare implements Comparator <Mountain> {
        public int compare(Mountain one, Mountain two) {
          return one.name. compareTo(two. name);
      }
      }
      class HeightCompare implements Comparator <Mountain> {
        public int compare(Mountain one, Mountain two) {
    return (two. height - one. height) ;
    }

      }
      public void go() {
            mtn.add(new Mountain("Longs ", 14255));
            mtn.add(new Mountain("Elbert ", 14433));
            mtn.add(new Mountain("Maroon " , 14156));
            mtn.add(new Mountain("Castle ", 14265));

            System.out.println("as entered:\n" + mtn);
            NameCompare nc = new NameCompare();
            Collections.sort(mtn, nc);
            System.out.println("by name:\n'" + mtn);
            HeightCompare hc = new HeightCompare();
            Collections.sort(mtn, hc);
            System.out.println("by height:\n " + mtn);
          }
    public static void main(String args[]){

        sortMountains   sorting=new sortMountains();
        sorting.go();
         //error line   Mountain a=new Mountain("Everest",12121);
    }

    }

上面的代码在没有错误的情况下编译正常，但是当我想在main方法中创建Mountain对象时，出现错误“无法从静态方法引用非静态”

最佳答案

使Mountain类static如下所示：

static class Mountain {
   ...

如果不这样做，则每个Mountain实例都必须具有一个与之关联的sortMountains实例。由于main()中没有这样的实例（方法本身是static），因此编译器不允许您在其中实例化Mountain。

有关更多讨论，请参见：


Java: Static vs non static inner class
Java inner class and static nested class

关于java - 不允许在main方法中声明，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13507952/