class T {
  public static void main(String[] args) {
    System.out.println(getSecondMax(new int[] { 1, 3, 5, 7, 9, 2, 4, 6, 8, 10 }));
  }

  /**
   * 求整数数组的第2大的数,不许用排序算法
   * 
   * @param nums
   * @return
   */
  public static int getSecondMax(int[] all) {
    int max, max2;// 第一大，第二大数字
    max = all[0];
    max2 = all[1];
    if (max < max2) {
      max = all[1];
      max2 = all[0];
    }
    for (int i = 1; i < all.length; i++) {
      if (all[i] > max2) {
        if (all[i] > max) {
          max2 = max;// 原来最大值变第二大
          max = all[i];// 最大值更新为当前值
        } else
          max2 = all[i];// 当前值为第二大
      }
    }
    return max2;
  }
}

------解决方案--------------------
Java code
 
 public class BigNum { 
 	public static void main(String[] args) { 
 		int[] a = new int[]{1,684,-2,1564,6564,65,465,-465,464874,464874,464874,464874,9874,9546,-54,65,46,568,8,4685,6,8,46,846,8,6,8446,86,46,8,464874}; 
 		if(null != a && a.length>2)	printTheFirstBigNumAndTheSecondBigNumInIntArray(a); 
 	} 
 	 
 	public static void printTheFirstBigNumAndTheSecondBigNumInIntArray(int[] a) { 
 		int fMax = a[0]; 
 		int sMax = a[1]; 
 		 
 		if(fMax  < sMax) { 
 			fMax += sMax; 
 			sMax = fMax - sMax; 
 			fMax = fMax - sMax; 
 		} 
 		 
 		for(int i=2; i <a.length; i++) { 
 			if(fMax  < a[i]) { 
 				if(sMax  < fMax) { 
 					sMax = fMax; 
 				} 
 				fMax = a[i]; 
 			}else { 
 				if(fMax != a[i] && sMax  < a[i]) { 
 					sMax = a[i]; 
 				} 
 			} 
 		} 
 		System.out.println("fMax:\t" + fMax + "\nsMax:\t" + sMax); 
 	} 
 }