两个大数相乘，帮忙修改下代码，急～ 在线等～
package test_wanglei;

public class wang {

public int[] a1;
public int[] a2;
public int[][] a3;
public int[] a4;

public int[][] B1(int[] a1, int[] a2) {
for (int i = a1.length-1; i >= 1; i--) {
for (int j = a2.length-1; j >= 1; j--) {
int temp = a1[i] * a2[j];
if(temp >9){
a3[i][j-1] = a1[i] * a2[j - 1] + temp/10;
a3[i][j] = temp %10;
}
else a3[i][j] = temp;
}
}
return a3;
}

public int [] B2(int [][] a3){
for(int a = a3.length-1; a >=1; a--){
for(int b = a3.length-1; b >= 1; b--){
int add = 0;
add += a3[a][b];
if(add >9){
a4[a] = add % 10;
a4[a-1] = a4[a-1] + add/10;
}
else a4[a] = add;
}
}

return a4;
}

public static void main(String[] args) {
wang w = new wang();

int [] x= {1,2};
int [] y= {1,2};

int [][] c = w.B1(x, y);
int [] d = w.B2(c);
System.out.println("=====================");

for(int x1 = 1; x1 < d.length; x1++){
System.out.println(d[x1]);
}
}

}

[解决办法]
public int[][] B1(int[] a1, int[] a2) {
a3 = new int[a1.length][a2.length];
for (int i = a1.length-1; i >= 1; i--) {
for (int j = a2.length-1; j >= 1; j--) {
int temp = a1[i] * a2[j];
if(temp >9){
a3[i][j-1] = a1[i] * a2[j - 1] + temp/10;
a3[i][j] = temp %10;
}
else a3[i][j] = temp;
}
}
return a3;
}

public int [] B2(int [][] a3){
a4 = new int[a3.length];
for(int a = a3.length-1; a >=1; a--){
for(int b = a3.length-1; b >= 1; b--){
int add = 0;
add += a3[a][b];
if(add >9){
a4[a] = add % 10;
a4[a-1] = a4[a-1] + add/10;
}
else a4[a] = add;
}
}

return a4;
}

// 加上这两行就不报错了
[解决办法]

Java code

public  int[][] B1(int[] a1, int[] a2) {        a3 = new int[a1.length][a2.length];        for (int i = a1.length-1; i >= 0; i--) {             for (int j = a2.length-1; j >= 0; j--) {                int temp = a1[i] * a2[j];                System.out.println("a1["+i+"] * a2["+j+"] = " + temp);                if(temp > 9){                     a3[i][j-1] = a1[i] * a2[j - 1] + temp/10;                     a3[i][j] = temp %10;                 }                 else a3[i][j] = temp;             }         }         return a3;     }
[解决办法]
楼主给的分不多啊
Java code 
 
public class wang{    private int[] a;        private int[] b;        public wang(int[] a, int[] b)    {        this.a = a;        this.b = b;    }        public int[] getMultipleResult()    {        //判断参数是否为空        if(a == null || b == null)        {            throw new IllegalArgumentException("Nonillable parameter is null!");        }                //判断参数是否合法        for(int temp : a)        {            if(temp > 9)            {                throw new IllegalArgumentException("Array item must less than 9!");            }        }                for(int temp : b)        {            if(temp > 9)            {                throw new IllegalArgumentException("Array item must less than 9!");            }        }                //创建结果数组，两个数相乘，结果的积最大为两个乘数位数之和        int[] resultTemp = new int[a.length + b.length];                //模拟手乘竖式        //      1  2  3    --内层循环        //    * 4  5  6    --外层循环        //  -------------        for (int i = a.length - 1; i >= 0; i--)        {            for (int j = b.length - 1; j >= 0; j--)            {                int temp = a[i] * b[j];                resultTemp[i + j + 1] += temp;                                //处理进位                if(resultTemp[i + j + 1] > 9)                {                    int carry = resultTemp[i + j + 1];                    resultTemp[i + j + 1] %= 10;                    resultTemp[i + j] += (int)(carry / 10);                }            }        }        int[] result = null;        //找到第一个不为零的元素        for (int i = 0; i < resultTemp.length; i++)        {            if(resultTemp[i] != 0)            {                result = new int[resultTemp.length - i];                System.arraycopy(resultTemp, i, result, 0, result.length);                break;            }        }        return result;    }        public static void main(String[] args)    {        int[] x = { 9, 9, 9};        int[] y = { 9, 9, 9};                wang w = new wang(x, y);                int[] d = w.getMultipleResult();                System.out.println("=====================");        for (int i = 0; i < d.length; i++)        {            System.out.print(d[i]);        }    }    }