java 实现比较版本号功能

/** 
 * 比较版本号的大小,前者大则返回一个正数,后者大返回一个负数,相等则返回0 
 * @param version1 
 * @param version2 
 * @return 
 */ 
public static int compareVersion(String version1, String version2) throws Exception { 
  if (version1 == null || version2 == null) { 
    throw new Exception("compareVersion error:illegal params."); 
  } 
  String[] versionArray1 = version1.split("\\.");//注意此处为正则匹配，不能用"."； 
  String[] versionArray2 = version2.split("\\."); 
  int idx = 0; 
  int minLength = Math.min(versionArray1.length, versionArray2.length);//取最小长度值 
  int diff = 0; 
  while (idx < minLength 
      && (diff = versionArray1[idx].length() - versionArray2[idx].length()) == 0//先比较长度 
      && (diff = versionArray1[idx].compareTo(versionArray2[idx])) == 0) {//再比较字符 
    ++idx; 
  } 
  //如果已经分出大小，则直接返回，如果未分出大小，则再比较位数，有子版本的为大； 
  diff = (diff != 0) ? diff : versionArray1.length - versionArray2.length; 
  return diff; 
}