Java Version

A frequent computer science problem is comparing version numbers. Version numbers are like decimal numbers with multiple decimal points. One can not accurately compare version numbers as a string or a number. Often you want to see if a version is later than another version. Here's a Java class which goes about solving this problem.

<geshi lang="java"> public class Version implements Comparable, Serializable { private final int version[];

public Version(String version) { String[] split = version.split("\\."); this.version = new int[split.length]; for (int i = 0; i < split.length; i++) { String string = split[i]; this.version[i] = Integer.valueOf(string).intValue(); } } private static final long serialVersionUID = 5028475470314950450L;

public int compareTo(Object o) { if (this == o) return 0; final int[] other = ((Version) o).version; int length = Math.max(version.length, other.length); for(int i = 0; i < length; i++) { int x = (i < version.length) ? version[i] : 0; int y = (i < other.length) ? other[i] : 0; if (x < y) return -1; if (x > y) return 1; } return 0; }

public int hashCode() { final int prime = 31; int result = 1; result = prime * result + Version.hashCode(version); return result; }

public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; final Version other = (Version) obj; if (!Arrays.equals(version, other.version)) return false; return true; }

private static int hashCode(int[] array) { final int prime = 31; if (array == null) return 0; int result = 1; for (int index = 0; index < array.length; index++) { result = prime * result + array[index]; } return result; }

public String toString() { String s = ""; for (int i = 0; i < version.length; i++) { if (!"".equals(s)) s += "."; s += Integer.toString(version[i]); } return s; }

} </geshi>