是否有比较版本号的标准习语?我不能直接使用String compareTo,因为我还不知道点释放的最大数量是多少。我需要比较版本,并有以下保持正确:

1.0 < 1.1
1.0.1 < 1.1
1.9 < 1.10

当前回答

我喜欢@Peter Lawrey的想法,我把它扩展到更远的范围:

    /**
    * Normalize string array, 
    * Appends zeros if string from the array
    * has length smaller than the maxLen.
    **/
    private String normalize(String[] split, int maxLen){
        StringBuilder sb = new StringBuilder("");
        for(String s : split) {
            for(int i = 0; i<maxLen-s.length(); i++) sb.append('0');
            sb.append(s);
        }
        return sb.toString();
    }

    /**
    * Removes trailing zeros of the form '.00.0...00'
    * (and does not remove zeros from, say, '4.1.100')
    **/
    public String removeTrailingZeros(String s){
        int i = s.length()-1;
        int k = s.length()-1;
        while(i >= 0 && (s.charAt(i) == '.' || s.charAt(i) == '0')){
          if(s.charAt(i) == '.') k = i-1;
          i--;  
        } 
        return s.substring(0,k+1);
    }

    /**
    * Compares two versions(works for alphabets too),
    * Returns 1 if v1 > v2, returns 0 if v1 == v2,
    * and returns -1 if v1 < v2.
    **/
    public int compareVersion(String v1, String v2) {

        // Uncomment below two lines if for you, say, 4.1.0 is equal to 4.1
        // v1 = removeTrailingZeros(v1);
        // v2 = removeTrailingZeros(v2);

        String[] splitv1 = v1.split("\\.");
        String[] splitv2 = v2.split("\\.");
        int maxLen = 0;
        for(String str : splitv1) maxLen = Math.max(maxLen, str.length());
        for(String str : splitv2) maxLen = Math.max(maxLen, str.length());
        int cmp = normalize(splitv1, maxLen).compareTo(normalize(splitv2, maxLen));
        return cmp > 0 ? 1 : (cmp < 0 ? -1 : 0);
    }

希望它能帮助到别人。它通过了interviewbit和leetcode中的所有测试用例(需要取消compareVersion函数中的两行注释)。

很容易测试!

其他回答

我自己写了一个小函数。更简单地使用列表

 public static boolean checkVersionUpdate(String olderVerison, String newVersion) {
        if (olderVerison.length() == 0 || newVersion.length() == 0) {
            return false;
        }
        List<String> newVerList = Arrays.asList(newVersion.split("\\."));
        List<String> oldVerList = Arrays.asList(olderVerison.split("\\."));

        int diff = newVerList.size() - oldVerList.size();
        List<String> newList = new ArrayList<>();
        if (diff > 0) {
            newList.addAll(oldVerList);
            for (int i = 0; i < diff; i++) {
                newList.add("0");
            }
            return examineArray(newList, newVerList, diff);
        } else if (diff < 0) {
            newList.addAll(newVerList);
            for (int i = 0; i < -diff; i++) {
                newList.add("0");
            }
            return examineArray(oldVerList, newList, diff);
        } else {
            return examineArray(oldVerList, newVerList, diff);
        }

    }

    public static boolean examineArray(List<String> oldList, List<String> newList, int diff) {
        boolean newVersionGreater = false;
        for (int i = 0; i < oldList.size(); i++) {
            if (Integer.parseInt(newList.get(i)) > Integer.parseInt(oldList.get(i))) {
                newVersionGreater = true;
                break;
            } else if (Integer.parseInt(newList.get(i)) < Integer.parseInt(oldList.get(i))) {
                newVersionGreater = false;
                break;
            } else {
                newVersionGreater = diff > 0;
            }
        }

        return newVersionGreater;
    }

我创建了一个简单的实用程序,使用语义版本约定在Android平台上比较版本。所以它只适用于X.Y.Z (Major.Minor.Patch)格式的字符串,其中X、Y和Z是非负整数。你可以在我的GitHub上找到它。

方法version . compareversions (String v1, String v2)比较两个版本字符串。如果版本相等则返回0,如果版本v1在版本v2之前则返回1,如果版本v1在版本v2之后则返回-1,如果版本格式无效则返回-2。

我写了一个名为MgntUtils的开源库,它有一个用于字符串版本的实用程序。它正确地比较它们,适用于版本范围等等。下面是这个库javadoc参见方法TextUtils.comapreVersions(…)它已经被大量使用并经过了良好的测试。下面这篇文章描述了这个库以及如何获取它。它可以作为Maven工件和在github上获得(包括源代码和JavaDoc)

使用Java 8 Stream替换组件中的前导零。这段代码通过了interviewbit.com上的所有测试

public int compareVersion(String A, String B) {
    List<String> strList1 = Arrays.stream(A.split("\\."))
                                           .map(s -> s.replaceAll("^0+(?!$)", ""))
                                           .collect(Collectors.toList());
    List<String> strList2 = Arrays.stream(B.split("\\."))
                                           .map(s -> s.replaceAll("^0+(?!$)", ""))
                                           .collect(Collectors.toList());
    int len1 = strList1.size();
    int len2 = strList2.size();
    int i = 0;
    while(i < len1 && i < len2){
        if (strList1.get(i).length() > strList2.get(i).length()) return 1;
        if (strList1.get(i).length() < strList2.get(i).length()) return -1;
        int result = new Long(strList1.get(i)).compareTo(new Long(strList2.get(i)));
        if (result != 0) return result;
        i++;
    }
    while (i < len1){
        if (!strList1.get(i++).equals("0")) return 1;
    }
    while (i < len2){
        if (!strList2.get(i++).equals("0")) return -1;
    }
    return 0;
}

此代码尝试解决这种类型的比较版本。

大多数版本说明符,如>= 1.0,都是不言自明的。的 说明符~>具有特殊含义,最好通过示例来说明。~> 2.0.3是 与>= 2.0.3和< 2.1相同。~> 2.1与>= 2.1相同,且< 3.0.

public static boolean apply(String cmpDeviceVersion, String reqDeviceVersion)
{
    Boolean equal           = !cmpDeviceVersion.contains(">") && !cmpDeviceVersion.contains(">=") &&
                              !cmpDeviceVersion.contains("<") && !cmpDeviceVersion.contains("<=") &&
                              !cmpDeviceVersion.contains("~>");

    Boolean between         = cmpDeviceVersion.contains("~>");
    Boolean higher          = cmpDeviceVersion.contains(">") && !cmpDeviceVersion.contains(">=") && !cmpDeviceVersion.contains("~>");
    Boolean higherOrEqual   = cmpDeviceVersion.contains(">=");

    Boolean less            = cmpDeviceVersion.contains("<") && !cmpDeviceVersion.contains("<=");
    Boolean lessOrEqual     = cmpDeviceVersion.contains("<=");

    cmpDeviceVersion        = cmpDeviceVersion.replaceAll("[<>=~]", "");
    cmpDeviceVersion        = cmpDeviceVersion.trim();

    String[] version        = cmpDeviceVersion.split("\\.");
    String[] reqVersion     = reqDeviceVersion.split("\\.");

    if(equal)
    {
        return isEqual(version, reqVersion);
    }
    else if(between)
    {
        return isBetween(version, reqVersion);
    }
    else if(higher)
    {
        return isHigher(version, reqVersion);
    }
    else if(higherOrEqual)
    {
        return isEqual(version, reqVersion) || isHigher(version, reqVersion);
    }
    else if(less)
    {
        return isLess(version, reqVersion);
    }
    else if(lessOrEqual)
    {
        return isEqual(version, reqVersion) || isLess(version, reqVersion);
    }

    return false;
}

private static boolean isEqual(String[] version, String[] reqVersion)
{
    String strVersion = StringUtils.join(version);
    String strReqVersion = StringUtils.join(reqVersion);
    if(version.length > reqVersion.length)
    {
        Integer diff = version.length - reqVersion.length;
        strReqVersion += StringUtils.repeat(".0", diff);
    }
    else if(reqVersion.length > version.length)
    {
        Integer diff = reqVersion.length - version.length;
        strVersion += StringUtils.repeat(".0", diff);
    }

    return strVersion.equals(strReqVersion);
}

private static boolean isHigher(String[] version, String[] reqVersion)
{
    String strVersion = StringUtils.join(version);
    String strReqVersion = StringUtils.join(reqVersion);
    if(version.length > reqVersion.length)
    {
        Integer diff = version.length - reqVersion.length;
        strReqVersion += StringUtils.repeat(".0", diff);
    }
    else if(reqVersion.length > version.length)
    {
        Integer diff = reqVersion.length - version.length;
        strVersion += StringUtils.repeat(".0", diff);
    }

    return strReqVersion.compareTo(strVersion) > 0;
}

private static boolean isLess(String[] version, String[] reqVersion)
{
    String strVersion = StringUtils.join(version);
    String strReqVersion = StringUtils.join(reqVersion);
    if(version.length > reqVersion.length)
    {
        Integer diff = version.length - reqVersion.length;
        strReqVersion += StringUtils.repeat(".0", diff);
    }
    else if(reqVersion.length > version.length)
    {
        Integer diff = reqVersion.length - version.length;
        strVersion += StringUtils.repeat(".0", diff);
    }

    return strReqVersion.compareTo(strVersion) < 0;
}

private static boolean isBetween(String[] version, String[] reqVersion)
{
    return (isEqual(version, reqVersion) || isHigher(version, reqVersion)) &&
            isLess(getNextVersion(version), reqVersion);
}

private static String[] getNextVersion(String[] version)
{
    String[] nextVersion = new String[version.length];
    for(int i = version.length - 1; i >= 0 ; i--)
    {
        if(i == version.length - 1)
        {
            nextVersion[i] = "0";
        }
        else if((i == version.length - 2) && NumberUtils.isNumber(version[i]))
        {
            nextVersion[i] = String.valueOf(NumberUtils.toInt(version[i]) + 1);
        }
        else
        {
            nextVersion[i] = version[i];
        }
    }
    return nextVersion;
}