Mike - 2 years ago 119

Java Question

Possible Duplicate:

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.

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Answer Source

```
/**
* 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").
*
* @note It does not work if "1.10" is supposed to be equal to "1.10.0".
*
* @param str1 a string of ordinal numbers separated by decimal points.
* @param str2 a string of ordinal numbers separated by decimal points.
* @return The result is a negative integer if str1 is _numerically_ less than str2.
* The result is a positive integer if str1 is _numerically_ greater than str2.
* The result is zero if the strings are _numerically_ equal.
*/
public static int versionCompare(String str1, String str2) {
String[] vals1 = str1.split("\\.");
String[] vals2 = str2.split("\\.");
int i = 0;
// set index to first non-equal ordinal or length of shortest version string
while (i < vals1.length && i < vals2.length && vals1[i].equals(vals2[i])) {
i++;
}
// compare first non-equal ordinal number
if (i < vals1.length && i < vals2.length) {
int diff = Integer.valueOf(vals1[i]).compareTo(Integer.valueOf(vals2[i]));
return Integer.signum(diff);
}
// the strings are equal or one string is a substring of the other
// e.g. "1.2.3" = "1.2.3" or "1.2.3" < "1.2.3.4"
return Integer.signum(vals1.length - vals2.length);
}
```

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