How do you compare two version Strings in Java?

Question

Another solution for this old post (for those that it might help) :

public class Version implements Comparable<Version> {

    private String version;

    public final String get() {
        return this.version;
    }

    public Version(String version) {
        if(version == null)
            throw new IllegalArgumentException("Version can not be null");
        if(!version.matches("[0-9]+(\\.[0-9]+)*"))
            throw new IllegalArgumentException("Invalid version format");
        this.version = version;
    }

    @Override public int compareTo(Version that) {
        if(that == null)
            return 1;
        String[] thisParts = this.get().split("\\.");
        String[] thatParts = that.get().split("\\.");
        int length = Math.max(thisParts.length, thatParts.length);
        for(int i = 0; i < length; i++) {
            int thisPart = i < thisParts.length ?
                Integer.parseInt(thisParts[i]) : 0;
            int thatPart = i < thatParts.length ?
                Integer.parseInt(thatParts[i]) : 0;
            if(thisPart < thatPart)
                return -1;
            if(thisPart > thatPart)
                return 1;
        }
        return 0;
    }

    @Override public boolean equals(Object that) {
        if(this == that)
            return true;
        if(that == null)
            return false;
        if(this.getClass() != that.getClass())
            return false;
        return this.compareTo((Version) that) == 0;
    }

}

---

Version a = new Version("1.1");
Version b = new Version("1.1.1");
a.compareTo(b) // return -1 (a<b)
a.equals(b)    // return false

Version a = new Version("2.0");
Version b = new Version("1.9.9");
a.compareTo(b) // return 1 (a>b)
a.equals(b)    // return false

Version a = new Version("1.0");
Version b = new Version("1");
a.compareTo(b) // return 0 (a=b)
a.equals(b)    // return true

Version a = new Version("1");
Version b = null;
a.compareTo(b) // return 1 (a>b)
a.equals(b)    // return false

List<Version> versions = new ArrayList<Version>();
versions.add(new Version("2"));
versions.add(new Version("1.0.5"));
versions.add(new Version("1.01.0"));
versions.add(new Version("1.00.1"));
Collections.min(versions).get() // return min version
Collections.max(versions).get() // return max version

// WARNING
Version a = new Version("2.06");
Version b = new Version("2.060");
a.equals(b)    // return false

---

Edit:

@daiscog: Thank you for your remark, this piece of code has been developed for the Android platform and as recommended by Google, the method "matches" check the entire string unlike Java that uses a regulatory pattern. (Android documentation - JAVA documentation)

It's really easy using Maven:

import org.apache.maven.artifact.versioning.DefaultArtifactVersion;

DefaultArtifactVersion minVersion = new DefaultArtifactVersion("1.0.1");
DefaultArtifactVersion maxVersion = new DefaultArtifactVersion("1.10");

DefaultArtifactVersion version = new DefaultArtifactVersion("1.11");

if (version.compareTo(minVersion) < 0 || version.compareTo(maxVersion) > 0) {
    System.out.println("Sorry, your version is unsupported");
}

You can get the right dependency string for Maven Artifact from this page:

<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-artifact</artifactId>
<version>3.0.3</version>
</dependency>

Tokenize the strings with the dot as delimiter and then compare the integer translation side by side, beginning from the left.

You need to normalise the version strings so they can be compared. Something like

import java.util.regex.Pattern;

public class Main {
    public static void main(String... args) {
        compare("1.0", "1.1");
        compare("1.0.1", "1.1");
        compare("1.9", "1.10");
        compare("1.a", "1.9");
    }

    private static void compare(String v1, String v2) {
        String s1 = normalisedVersion(v1);
        String s2 = normalisedVersion(v2);
        int cmp = s1.compareTo(s2);
        String cmpStr = cmp < 0 ? "<" : cmp > 0 ? ">" : "==";
        System.out.printf("'%s' %s '%s'%n", v1, cmpStr, v2);
    }

    public static String normalisedVersion(String version) {
        return normalisedVersion(version, ".", 4);
    }

    public static String normalisedVersion(String version, String sep, int maxWidth) {
        String[] split = Pattern.compile(sep, Pattern.LITERAL).split(version);
        StringBuilder sb = new StringBuilder();
        for (String s : split) {
            sb.append(String.format("%" + maxWidth + 's', s));
        }
        return sb.toString();
    }
}

Prints

'1.0' < '1.1'
'1.0.1' < '1.1'
'1.9' < '1.10'
'1.a' > '1.9'

The best to reuse existing code, take Maven's ComparableVersion class

advantages:

• Apache License, Version 2.0,
• tested,
• used (copied) in multiple projects like spring-security-core, jboss etc
• multiple features
• it's already a java.lang.Comparable
• just copy-paste that one class, no third-party dependencies

Don't include dependency to maven-artifact as that will pull various transitive dependencies

// VersionComparator.java
import java.util.Comparator;

public class VersionComparator implements Comparator {

    public boolean equals(Object o1, Object o2) {
        return compare(o1, o2) == 0;
    }

    public int compare(Object o1, Object o2) {
        String version1 = (String) o1;
        String version2 = (String) o2;

        VersionTokenizer tokenizer1 = new VersionTokenizer(version1);
        VersionTokenizer tokenizer2 = new VersionTokenizer(version2);

        int number1 = 0, number2 = 0;
        String suffix1 = "", suffix2 = "";

        while (tokenizer1.MoveNext()) {
            if (!tokenizer2.MoveNext()) {
                do {
                    number1 = tokenizer1.getNumber();
                    suffix1 = tokenizer1.getSuffix();
                    if (number1 != 0 || suffix1.length() != 0) {
                        // Version one is longer than number two, and non-zero
                        return 1;
                    }
                }
                while (tokenizer1.MoveNext());

                // Version one is longer than version two, but zero
                return 0;
            }

            number1 = tokenizer1.getNumber();
            suffix1 = tokenizer1.getSuffix();
            number2 = tokenizer2.getNumber();
            suffix2 = tokenizer2.getSuffix();

            if (number1 < number2) {
                // Number one is less than number two
                return -1;
            }
            if (number1 > number2) {
                // Number one is greater than number two
                return 1;
            }

            boolean empty1 = suffix1.length() == 0;
            boolean empty2 = suffix2.length() == 0;

            if (empty1 && empty2) continue; // No suffixes
            if (empty1) return 1; // First suffix is empty (1.2 > 1.2b)
            if (empty2) return -1; // Second suffix is empty (1.2a < 1.2)

            // Lexical comparison of suffixes
            int result = suffix1.compareTo(suffix2);
            if (result != 0) return result;

        }
        if (tokenizer2.MoveNext()) {
            do {
                number2 = tokenizer2.getNumber();
                suffix2 = tokenizer2.getSuffix();
                if (number2 != 0 || suffix2.length() != 0) {
                    // Version one is longer than version two, and non-zero
                    return -1;
                }
            }
            while (tokenizer2.MoveNext());

            // Version two is longer than version one, but zero
            return 0;
        }
        return 0;
    }
}

// VersionTokenizer.java
public class VersionTokenizer {
    private final String _versionString;
    private final int _length;

    private int _position;
    private int _number;
    private String _suffix;
    private boolean _hasValue;

    public int getNumber() {
        return _number;
    }

    public String getSuffix() {
        return _suffix;
    }

    public boolean hasValue() {
        return _hasValue;
    }

    public VersionTokenizer(String versionString) {
        if (versionString == null)
            throw new IllegalArgumentException("versionString is null");

        _versionString = versionString;
        _length = versionString.length();
    }

    public boolean MoveNext() {
        _number = 0;
        _suffix = "";
        _hasValue = false;

        // No more characters
        if (_position >= _length)
            return false;

        _hasValue = true;

        while (_position < _length) {
            char c = _versionString.charAt(_position);
            if (c < '0' || c > '9') break;
            _number = _number * 10 + (c - '0');
            _position++;
        }

        int suffixStart = _position;

        while (_position < _length) {
            char c = _versionString.charAt(_position);
            if (c == '.') break;
            _position++;
        }

        _suffix = _versionString.substring(suffixStart, _position);

        if (_position < _length) _position++;

        return true;
    }
}

Example:

public class Main
{
    private static VersionComparator cmp;

    public static void main (String[] args)
    {
        cmp = new VersionComparator();
        Test(new String[]{"1.1.2", "1.2", "1.2.0", "1.2.1", "1.12"});
        Test(new String[]{"1.3", "1.3a", "1.3b", "1.3-SNAPSHOT"});
    }

    private static void Test(String[] versions) {
        for (int i = 0; i < versions.length; i++) {
            for (int j = i; j < versions.length; j++) {
                Test(versions[i], versions[j]);
            }
        }
    }

    private static void Test(String v1, String v2) {
        int result = cmp.compare(v1, v2);
        String op = "==";
        if (result < 0) op = "<";
        if (result > 0) op = ">";
        System.out.printf("%s %s %s\n", v1, op, v2);
    }
}

Output:

1.1.2 == 1.1.2                --->  same length and value
1.1.2 < 1.2                   --->  first number (1) less than second number (2) => -1
1.1.2 < 1.2.0                 --->  first number (1) less than second number (2) => -1
1.1.2 < 1.2.1                 --->  first number (1) less than second number (2) => -1
1.1.2 < 1.12                  --->  first number (1) less than second number (12) => -1
1.2 == 1.2                    --->  same length and value
1.2 == 1.2.0                  --->  first shorter than second, but zero
1.2 < 1.2.1                   --->  first shorter than second, and non-zero
1.2 < 1.12                    --->  first number (2) less than second number (12) => -1
1.2.0 == 1.2.0                --->  same length and value
1.2.0 < 1.2.1                 --->  first number (0) less than second number (1) => -1
1.2.0 < 1.12                  --->  first number (2) less than second number (12) => -1
1.2.1 == 1.2.1                --->  same length and value
1.2.1 < 1.12                  --->  first number (2) less than second number (12) => -1
1.12 == 1.12                  --->  same length and value

1.3 == 1.3                    --->  same length and value
1.3 > 1.3a                    --->  first suffix ('') is empty, but not second ('a') => 1
1.3 > 1.3b                    --->  first suffix ('') is empty, but not second ('b') => 1
1.3 > 1.3-SNAPSHOT            --->  first suffix ('') is empty, but not second ('-SNAPSHOT') => 1
1.3a == 1.3a                  --->  same length and value
1.3a < 1.3b                   --->  first suffix ('a') compared to second suffix ('b') => -1
1.3a < 1.3-SNAPSHOT           --->  first suffix ('a') compared to second suffix ('-SNAPSHOT') => -1
1.3b == 1.3b                  --->  same length and value
1.3b < 1.3-SNAPSHOT           --->  first suffix ('b') compared to second suffix ('-SNAPSHOT') => -1
1.3-SNAPSHOT == 1.3-SNAPSHOT  --->  same length and value