初学不懂，请高手帮看一下


         public class ArrayDemoTester
{
public static void main(String[] args)
{
ArrayDemo.declareArray();
ArrayDemo.creatArray();
ArrayDemo.initializeArray();
ArrayDemo.outputArray(); int[] a =ArrayDemo.getInputArray();
System.out.println("a="+ArrayDemo.arrayToString(a));
System.out.println("max(a)=a["+ArrayDemo.indexOfMax(a)+"]"+ArrayDemo.max(a));
System.out.println("min(a="+ArrayDemo.min(a));
ArrayDemo.expandCapacity(a);
System.out.println("a="+ArrayDemo.arrayToString(a));
a=ArrayDemo.expand(a);
System.out.println("a="+ArrayDemo.arrayToString(a));
}
}  
    public class ArrayDemo
    {
     public static final int MAX_SIZE=9;
     public static final int MAX_RANDOM_INT=36;
    
    
     public static void  declareArray()
     {
     System.out.println("declareArray...");
     int[] x =null;
     System.out.println("int[] x;// x="+x);
     System.out.println();
     }
    
        public static void creatArray()
        {
         System.out.println("creatArray...");
         int[] x=new int[MAX_SIZE];
         System.out.println("int[] x=new int[MAX_SIZE];// x="+x);
         System.out.println("x="+arrayToString(x));
         System.out.println();
        
        
        }
    
        public static void initializeArray()
        {
         System.out.println("initializeArray...");
         int[] x=new int[MAX_SIZE];
         System.out.println("int[] x=new int[MAX_SIZE];// x="+x);
         for(int i=0;i<x.length;i++)
         {
         x[i]=2*i;
         }
         System.out.println("foreach i do x[i]=2*i; //x="+x);
         System.out.println("x="+arrayToString(x));
         System.out.println();
        
        }
        
        
        
        public static void outputArray()
        {
         System.out.println("outputArray...");
         int[] x={1,1,2,3,5,8,13};
         for(int i=0;i<x.length;i++)
         {
         System.out.println(x[i]+" ");
        
         }
         System.out.println();
         char[] city={'Y','a','n','g','z','h','o','u'};
         System.out.println(city);
         System.out.println();
        
        }
        
        
    
        
        public static int max(int[] x)
        {
         int maxValue=x[0];
         for(int i=0;i<x.length;i++)
         {
         maxValue=Math.max(maxValue,x[i]);
        
         }
         return maxValue;
        
        }
    
    
    
    
        public static int min(int[] x)
        {
         return min(x,x.length);
        
        }
         private static int min(int[] x,int size)
         {
          if(size==1)
          {
          return x[0];
         
          }
          else if (size==2)
          {
          return Math.min(x[0],x[1]);
         
          }
          else 
          {
          return Math.min(min(x,size-1),x[size-1]);
          }
         }
         
         
         
         public static int indexOfMax(int[] x)
         {
          int index=0;
          for(int i=0;i<x.length;i++)
          {
          if(x[i]>x[index])
          {
          index=i;
          }
          }
          return index;
         }
         
         
         /**
          *从控制台接受任意个整数，以数组形式返回
          */
         public static void randomArray()
         {
          System.out.println("randomArray...");
          int[] x=new int[MAX_SIZE];
          for(int i=0;i<x.length;i++)
          {
          x[i]=RandomDemo.randomInt(MAX_RANDOM_INT);
          }
          System.out.println("x="+arrayToString(x));
         System.out.println();
        
         
         }                   
         
         
         
         public static  int[] getInputArray()
         {
          System.out.println("getInputArray..");
          java.util.Scanner sc=new java.util.Scanner(System.in);
          String buffer="";
          System.out.println("输入任意个整数");
          int counter=0;
          while(sc.hasNextInt())
          {
          counter++;
          buffer=buffer+sc.nextInt()+" ";
         
          }
         
          java.util.Scanner scanner=new java.util.Scanner(buffer);
          int[] x=new int[counter];
          counter=0;
          while(scanner.hasNextInt())
          {
          x[counter++]=scanner.nextInt();
          }
         
          return x;
         }
         
         
         
         
         public static String arrayToString(int[] x)
         {
          if (x==null) return "null";
          if (x.length==0 )  return "[]";
          StringBuilder buffer=new StringBuilder();
          buffer.append("[").append(x[0]);
          for(int i=1;i<x.length;i++)
          {
          buffer.append(",").append(x[i]);
          }
         
          buffer.append("]");
          return buffer.toString();
          }
         
         
         
         
          
          public  static  void expandCapacity(int[] x)
          {
           int newCapacity=(x.length+1)*2;
           if(newCapacity<0)
           {
           newCapacity=Integer.MAX_VALUE;
           }
          
           int[]  temp=new int[newCapacity];
          
           for(int i=0;i<x.length;i++)
           {
           temp[i]=x[i];
           }
           x=temp;
          
          }
          
          
          
          
          public static int[] expand(int[] x)
          {
           int newCapacity=(x.length+1)*2;
           if(newCapacity<0)
           {
           newCapacity=Integer.MAX_VALUE;
           }
          
           int[]  newArray=new int[newCapacity];
           for(int i=0;i<x.length;i++)
           {
           newArray[i]=x[i];
           }
          
           return newArray;
          
          }
          
          
}
--------------------Configuration: <Default>--------------------
F:\java\ArrayDemoTester.java:22: 类 ArrayDemo 是公共的，应在名为 ArrayDemo.java 的文件中声明
    public class ArrayDemo
           ^
F:\java\ArrayDemoTester.java:146: 找不到符号
符号： 变量 RandomDemo
位置： 类 ArrayDemo
                        x[i]=RandomDemo.randomInt(MAX_RANDOM_INT);
                             ^
2 错误Process completed.
问题在哪啊