首先，将乘数和被乘数按照每三位进行划分，列出乘法表，乘数和被乘数的地位分别放在表格的右端和上端。

    8  216  547

         96   785

计算表格中的数值

8	216	547	*
768	20736	52512	96
6250	169560	429395	785

 向右错位后按列相加

768	20736	52512
	6250	169560	429395
768	27016	222072	429395

最后一行，从个位数开始，以1000进制进行进位，超出1000的部分进位到前一个方格里：

	768	27016	222072	429395
	768+27=795	27016+222=27238	222072+429=222501	留395进429
	795	238	501	395

最后一排的最前端的方格可以不用再往前进位，所以8216547*96785 = 795238501395

import java.awt.List;
import java.util.Scanner;

/**
 * 
 * @author yyc 大整数乘法：采用“表格法”
 */
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		// 输入乘数与被乘数
		Scanner scanner = new Scanner(System.in);
		String mulStrA = scanner.nextLine();
		String mulStrB = scanner.nextLine();

		// 求得乘积
		String resultStr = BigIntegerMul(mulStrA, mulStrB);

		System.out.println(resultStr);
	}

	public static String BigIntegerMul(String mulStrA, String mulStrB) {

		int[] mListA = SplitToArray(mulStrA);
		int[] mListB = SplitToArray(mulStrB);

		int[][] mulArray = new int[mListA.length][mListB.length];

		// 计算表格
		for (int i = 0; i < mListA.length; i++) {
			for (int j = 0; j < mListB.length; j++) {
				mulArray[i][j] = mListA[i] * mListB[j];
			}
		}

		// 错位累加
		int[] reArray = new int[mListA.length + mListB.length + 1];
		int lastEffectIndex = 0;

		for (int n = 0; n < reArray.length; n++) {
			int iniRe = 0;
			for (int j = n; j >= 0; j--) {
				int i = n - j;

				if ((j < mListB.length) && (i < mListA.length)) {
					iniRe += mulArray[i][j];

					lastEffectIndex = n;
				}
			}
			reArray[n] = iniRe;
		}

		// 进位操作
		for (int i = lastEffectIndex; i > 0; i--) {
			reArray[i - 1] += reArray[i] / 1000;
			reArray[i] = reArray[i] % 1000;
		}

		// 拼接结果
		StringBuffer sBuffer = new StringBuffer();
		for (int i = 0; i <= lastEffectIndex; i++) {

			String string = ((Integer) reArray[i]).toString();
			for (int j = 0; j < 3 - string.length(); j++) {
				sBuffer.append("0");
			}
			sBuffer.append(string);
		}

		return sBuffer.toString();

	}

	public static int[] SplitToArray(String mulStr) {
		// 将乘数与被乘数从各位开始，每三位划分，放入数据
		int len = (int) Math.ceil(((double) mulStr.length()) / 3);
		int[] mList = new int[len];

		int i = mulStr.length() - 1;
		int n = len - 1;
		while (i >= 0) {
			StringBuffer sb = new StringBuffer();
			int interval = 3;
			if (i < 2) {
				interval = i + 1;
			}

			for (int j = interval - 1; j >= 0; j--) {
				sb.append(mulStr.charAt(i - j));
			}

			mList[n] = Integer.parseInt(sb.toString());
			n--;
			i -= interval;
		}
		return mList;
	}

}