用递归方法产生格雷码；

public class ThrowDemo02{
public static void main(String[] args) {   
    String[] strArr = GrayCode(3);//产生8位的格雷码
    for(int i = 0 ; i < strArr.length ; i++){
        System.out.println(strArr[i]);
    }
   }
    public static String[] GrayCode(int n) {
    String[] grayCodeArr = new String[(int)Math.pow(2, n)];   
    if(n < 1){
        System.out.println("你输入的格雷码位数有误！");
    }  
    if(1 == n){
        grayCodeArr[0] = "0";
        grayCodeArr[1] = "1";
        return grayCodeArr;
    }
    String[] before = GrayCode(n-1); //递归调用  
    for(int i = 0 ; i < before.length ; i++){
        grayCodeArr[i] = "0" + before[i];
        grayCodeArr[grayCodeArr.length -1 - i] = "1" + before[i];
    } 
    return grayCodeArr;  
    }
}