Returns the path will relative path segments like ".." - Android File Input Output

Android examples for File Input Output:File Path

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Description

Returns the path will relative path segments like ".."

Demo Code

/*//  w  w w.  j  av a 2s.co m
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//package com.java2s;

public class Main {
    /**
     * Returns the path will relative path segments like ".." and "." resolved.
     * The returned path will not necessarily start with a "/" character. This
     * handles ".." and "." segments at both the beginning and end of the path.
     *
     * @param discardRelativePrefix true to remove leading ".." segments from
     *     the path. This is appropriate for paths that are known to be
     *     absolute.
     */
    public static String canonicalizePath(String path,
            boolean discardRelativePrefix) {
        // the first character of the current path segment
        int segmentStart = 0;

        // the number of segments seen thus far that can be erased by sequences of '..'.
        int deletableSegments = 0;

        for (int i = 0; i <= path.length();) {
            int nextSegmentStart;
            if (i == path.length()) {
                nextSegmentStart = i;
            } else if (path.charAt(i) == '/') {
                nextSegmentStart = i + 1;
            } else {
                i++;
                continue;
            }

            /*
             * We've encountered either the end of a segment or the end of the
             * complete path. If the final segment was "." or "..", remove the
             * appropriate segments of the path.
             */
            if (i == segmentStart + 1
                    && path.regionMatches(segmentStart, ".", 0, 1)) {
                // Given "abc/def/./ghi", remove "./" to get "abc/def/ghi".
                path = path.substring(0, segmentStart)
                        + path.substring(nextSegmentStart);
                i = segmentStart;
            } else if (i == segmentStart + 2
                    && path.regionMatches(segmentStart, "..", 0, 2)) {
                if (deletableSegments > 0 || discardRelativePrefix) {
                    // Given "abc/def/../ghi", remove "def/../" to get "abc/ghi".
                    deletableSegments--;
                    int prevSegmentStart = path.lastIndexOf('/',
                            segmentStart - 2) + 1;
                    path = path.substring(0, prevSegmentStart)
                            + path.substring(nextSegmentStart);
                    i = segmentStart = prevSegmentStart;
                } else {
                    // There's no segment to delete; this ".." segment must be retained.
                    i++;
                    segmentStart = i;
                }
            } else {
                if (i > 0) {
                    deletableSegments++;
                }
                i++;
                segmentStart = i;
            }
        }
        return path;
    }
}

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