public static void dd(int n)
    {
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<=i+1;j++)
            {
                System.out.print("*");
            }
            System.out.print("\n");
        }
        for(int i=n;i>0;i--)
        {
            for(int j=0;j<i+1;j++)
            {
                System.out.print("*");
            }
            System.out.print("\n");
        }
    }

------解决方案--------------------
这样行不？
public class test{
	public test(int len){
		System.out.println(f(len,len,len));
	}
	public String f(int x,int y,int len){
		return y<0?"":(x<=len/2-Math.abs(y-len/2-1)?"*":" ")+(x==len?"\n":"")+f(x==0?len:x-1,x==0?y-1:y,len);
	}
	public static void main(String args[]){
		new test(7);
	}
}

------解决方案--------------------
[code=java] 
 public class PrintSign{ 
  private static final int N = 5; 
 public static void main(String[] args) { 
     for(int i=1; i <=N; i++) { 
        System.out.println(PrintSign.Sign(i)); 
      } 
     for(int i=N; i>0; i--) { 
        System.out.println(PrintSign.Sign(i)); 
      } 
    
   } 
   public static String Sign(int n) { 
     if (n == 1) 
      return "*"; 
     else 
       return ("*" + Sign(n-1)); 
  
  } 
 } 
 [/code]

------解决方案--------------------
Java code

public   class   PrintSign{ 
      private   static   final   int   N   =   5; 
public   static   void   main(String[]   args)   { 
                for(int   i=1;   i <=N;   i++)   { 
                          System.out.println(PrintSign.Sign(i)); 
                  } 
                for(int   i=N;   i> 0;   i--)   { 
                          System.out.println(PrintSign.Sign(i)); 
                  } 
            
        } 
        public   static   String   Sign(int   n)   { 
                if   (n   ==   1) 
                      return   "*"; 
                else 
                        return   ("*"   +   Sign(n-1)); 
    
      } 
}