public class BigIntAdd {
	private int[] array;
	//聲明一個數(shù)組 
	//計算大數(shù)相加的函數(shù) 
	public static String bigAdd(BigIntAdd fisrtNum, BigIntAdd secondNum) {
		String result = "";
		Boolean falg = false;
		//判斷數(shù)組是否越界的標志 
		int[] arrayOne;
		int[] arrayTwo;
		int[] arrayThree = null;
		//把較長的字符串放到arrayOne數(shù)組中，因為要把計算結果放到arrayOne數(shù)組中 
		if (fisrtNum.instance().length >= secondNum.instance().length) {
			arrayOne = fisrtNum.instance();
			arrayTwo = secondNum.instance();
		} else {
			arrayOne = secondNum.instance();
			arrayTwo = fisrtNum.instance();
		}
		for (int i = 0; i < arrayTwo.length; i++) {
			if (arrayOne[i] + arrayTwo[i] < 10) {
				//不需要進位時 
				arrayOne[i] = arrayOne[i] + arrayTwo[i];
			} else if (arrayOne[i] + arrayTwo[i] >= 10) {
				//需要進位時 
				arrayOne[i] = arrayOne[i] + arrayTwo[i] - 10;
				if ((i + 1) < arrayOne.length) {
					arrayOne[i + 1] = arrayOne[i + 1] + 1;
					//下一位的值加1
				} else {
					//當arrayOne的長度不夠時要把其復制到arrayThree中 
					falg = true;
					arrayThree = new int[arrayOne.length + 1];
					System.arraycopy(arrayOne, 0, arrayThree, 0,arrayOne.length);
					arrayThree[arrayOne.length] = 1;
					//把arrayThree最高位賦值1，等價于進位的1
				}
			}
		}
		//把數(shù)組arrayThree中的元素全部的拼接為字符串 
		if (falg) {
			for (int i : arrayThree) {
				result += i;
			}
		} else {
			for (int i : arrayOne) {
				result += i;
			}
		}
		//把結果反轉返回 
		return new StringBuffer(result).reverse().toString();
	}
	//初始化數(shù)組方法 
	private int[] instance() {
		return array;
	}
	//初始化構造方法 
	public BigIntAdd(String num) {
		StringBuffer sb = new StringBuffer(num);
		String string = sb.reverse().toString();
		//實現(xiàn)字符串反轉，便于計算 
		array = new int[string.length()];
		//把字符串轉化為數(shù)組 
		for (int i = 0; i < string.length(); i++) {
			array[i] = Integer.valueOf(string.substring(i, i + 1));
		}
	}
	public static void main(String [] args){
		String result=BigIntAdd.bigAdd(new BigIntAdd("5211111111"), new BigIntAdd("4099999999"));
		System.out.println(result);
	}
}