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Compute relative path from a directory to other file or directory.
/*
* by Shigeru KANEMOTO at SWITCHSCIENCE.
*/
import java.io.File;
import java.io.IOException;
class RelativePath {
//
// Compute relative path to "target" from a directory "origin".
//
// If "origin" is not absolute, it is relative from the current directory.
// If "target" is not absolute, it is relative from "origin".
//
public static String relativePath(String origin, String target) {
try {
origin = (new File(origin)).getCanonicalPath();
File targetFile = new File(target);
if (targetFile.isAbsolute())
target = targetFile.getCanonicalPath();
else
target = (new File(origin, target)).getCanonicalPath();
}
catch (IOException e) {
return null;
}
if (origin.equals(target)) {
// origin and target is identical.
return ".";
}
if (origin.equals(File.separator)) {
// origin is root.
return "." + target;
}
String prefix = "";
String root = File.separator;
if (System.getProperty("os.name").indexOf("Windows") != -1) {
if (origin.startsWith("\\\\") || target.startsWith("\\\\")) {
// Windows UNC path not supported.
return null;
}
char originLetter = origin.charAt(0);
char targetLetter = target.charAt(0);
if (Character.isLetter(originLetter) && Character.isLetter(targetLetter)) {
// Windows only
if (originLetter != targetLetter) {
// Drive letters differ
return null;
}
}
prefix = "" + originLetter + ':';
root = prefix + File.separator;
}
String relative = "";
while (!target.startsWith(origin + File.separator)) {
origin = (new File(origin)).getParent();
if (origin.equals(root))
origin = prefix;
relative += "..";
relative += File.separator;
}
return relative + target.substring(origin.length() + 1);
}
}
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