Efficient way to compare version strings in Java [duplicate]

Answer 1

Split the String on "." or whatever your delimeter will be, then parse each of those tokens to the Integer value and compare.

int compareStringIntegerValue(String s1, String s2, String delimeter)  
{  
   String[] s1Tokens = s1.split(delimeter);  
   String[] s2Tokens = s2.split(delimeter);  

   int returnValue = 0;
   if(s1Tokens.length > s2Tokens.length)  
   {  
       for(int i = 0; i<s1Tokens.length; i++)  
       {  
          int s1Value = Integer.parseString(s1Tokens[i]);  
          int s2Value = Integer.parseString(s2Tokens[i]);  
          Integer s1Integer = new Integer(s1Value);  
          Integer s2Integer = new Integer(s2Value);  
          returnValue = s1Integer.compareTo(s2Value);
          if( 0 == isEqual)  
           {  
              continue; 
           }  
           return returnValue;  //end execution
        }
           return returnValue;  //values are equal
 } 

I will leave the other if statement as an exercise.

Answer 2

Split them into arrays and then compare.

// check if two strings are equal. If they are return 0;
String[] a1;

String[] a2;

int i = 0;

while (true) {
    if (i == a1.length && i < a2.length) return -1;
    else if (i < a1.length && i == a2.length) return 1;

    if (a1[i].equals(a2[i]) {
       i++;
       continue;
    }
     return a1[i].compareTo(a2[i];
}
return 0;

Answer 3

This is almost certainly not the most efficient way to do it, but given that version number strings will almost always be only a few characters long I don't think it's worth optimizing further:

public static int compareVersions(String v1, String v2) {
    String[] components1 = v1.split("\\.");
    String[] components2 = v2.split("\\.");
    int length = Math.min(components1.length, components2.length);
    for(int i = 0; i < length; i++) {
        int result = new Integer(components1[i]).compareTo(Integer.parseInt(components2[i]));
        if(result != 0) {
            return result;
        }
    }
    return Integer.compare(components1.length, components2.length);
}

Answer 4

Comparing version strings can be a mess; you're getting unhelpful answers because the only way to make this work is to be very specific about what your ordering convention is. I've seen one relatively short and complete version comparison function on a blog post, with the code placed in the public domain- it isn't in Java but it should be simple to see how to adapt this.