Efficient way to compare version strings in Java

Question

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How do you compare two version Strings in Java?

I've 2 strings which contains version information as shown below:

str1 = "1.2"
str2 = "1.1.2"

Now, can any one tell me the efficient way to compare these versions inside strings in Java & return 0 , if they're equal, -1, if str1 < str2 & 1 if str1>str2.

Answer 1

Requires commons-lang3-3.8.1.jar for string operations.

/**
 * Compares two version strings. 
 * 
 * Use this instead of String.compareTo() for a non-lexicographical 
 * comparison that works for version strings. e.g. "1.10".compareTo("1.6").
 * 
 * @param v1 a string of alpha numerals separated by decimal points. 
 * @param v2 a string of alpha numerals separated by decimal points.
 * @return The result is 1 if v1 is greater than v2. 
 *         The result is 2 if v2 is greater than v1. 
 *         The result is -1 if the version format is unrecognized. 
 *         The result is zero if the strings are equal.
 */

public int VersionCompare(String v1,String v2)
{
    int v1Len=StringUtils.countMatches(v1,".");
    int v2Len=StringUtils.countMatches(v2,".");

    if(v1Len!=v2Len)
    {
        int count=Math.abs(v1Len-v2Len);
        if(v1Len>v2Len)
            for(int i=1;i<=count;i++)
                v2+=".0";
        else
            for(int i=1;i<=count;i++)
                v1+=".0";
    }

    if(v1.equals(v2))
        return 0;

    String[] v1Str=StringUtils.split(v1, ".");
    String[] v2Str=StringUtils.split(v2, ".");
    for(int i=0;i<v1Str.length;i++)
    {
        String str1="",str2="";
        for (char c : v1Str[i].toCharArray()) {
            if(Character.isLetter(c))
            {
                int u=c-'a'+1;
                if(u<10)
                    str1+=String.valueOf("0"+u);
                else
                    str1+=String.valueOf(u);
            }
            else
                str1+=String.valueOf(c);
        }            
        for (char c : v2Str[i].toCharArray()) {
            if(Character.isLetter(c))
            {
                int u=c-'a'+1;
                if(u<10)
                    str2+=String.valueOf("0"+u);
                else
                    str2+=String.valueOf(u);
            }
            else
                str2+=String.valueOf(c);
        }
        v1Str[i]="1"+str1;
        v2Str[i]="1"+str2;

            int num1=Integer.parseInt(v1Str[i]);
            int num2=Integer.parseInt(v2Str[i]);

            if(num1!=num2)
            {
                if(num1>num2)
                    return 1;
                else
                    return 2;
            }
    }
    return -1;
}