将数字转为指定长度的字符串，如果位数不够，添加前缀 0
呃。。。好象可以用 java.text.DecimalFormat。。。先研究一下这个类。

/** * 将数字转为指定长度的字符串，如果位数不够，添加前缀 0 * @param value * @param length * @return */private static String i2s(int value, int length){//System.out.println("value:" + value);//System.out.println("length:" + length);String s = String.valueOf(value);if(s.length()>length){throw new RuntimeException("length is too short.");}else if(s.length()==length){return s;}else{char[] cc = new char[length];int i=0;for(; i<length - s.length(); i++){cc[i] = '0';}for(; i<length; i++){//System.out.println(i);cc[i] = s.charAt(length - i - 1); //这里容易出错：length - i - 1}return new String(cc);}}private static void testI2s(){for (int i = 0; i < 1050; i++) {System.out.println(i2s(i, 3));}}

private static String i2s_02(int value, int length){//java.util.Formatter//DecimalFormat df = new DecimalFormat("###");//DecimalFormat df = new DecimalFormat("000");char[] cc = new char[length];int i=0;for(i=0; i<length; i++){//cc[i] = '#';cc[i] = '0';}DecimalFormat df = new DecimalFormat( new String(cc) );String s = df.format(value);if(s.length()>length){throw new RuntimeException("length is too short.");}return s;}private static void testI2s_02(){for (int i = 0; i < 1050; i++) {System.out.println(i2s_02(i, 3));}}