java - "directories-first"订单的比较器<文件>

Question

我很难过...假设我有这个目录树:

{someRoot}/
{someRoot}/bar/
{someRoot}/bar/file1.txt
{someRoot}/foo/
{someRoot}/foo/baz/
{someRoot}/foo/baz/file3.txt
{someRoot}/foo/abracadabra.txt
{someRoot}/foo/file2.txt
{someRoot}/aardvark.txt
{someRoot}/food.txt
{someRoot}/zebra.txt

您会注意到顺序。调用此 order1。在每个阶段，目录先于文件。 (注意: bar/file1.txt 出现在 foo 之前，因此在全局范围内，目录并不都出现在所有文件之前。)

如果我枚举这个目录树，然后递归枚举子目录，我将得到以下 List<File> , 排序 order2。

{someRoot}/
{someRoot}/aardvark.txt
{someRoot}/bar/
{someRoot}/foo/
{someRoot}/food.txt
{someRoot}/zebra.txt
{someRoot}/bar/file1.txt
{someRoot}/foo/abracadabra.txt
{someRoot}/foo/baz/
{someRoot}/foo/file2.txt
{someRoot}/foo/baz/file3.txt

如果我创建简单的 Comparator<File> :

Comparator<File> fc = new Comparator<File>(){
    @Override public int compare(File o1, File o2) {
        return o1.compareTo(o2);
    }
};

然后我排序，我从字典顺序得到这个顺序 (order3):

{someRoot}
{someRoot}/aardvark.txt
{someRoot}/bar
{someRoot}/bar/file1.txt
{someRoot}/foo
{someRoot}/food.txt
{someRoot}/foo/abracadabra.txt
{someRoot}/foo/baz
{someRoot}/foo/baz/file3.txt
{someRoot}/foo/file2.txt
{someRoot}/zebra.txt

但我不想要这种排序(它有问题:注意 food.txt 位于目录 foo 及其子项之间)，我想要 order1。我怎样才能写一个比较器来得到它？

Answer 1

这在我的测试中有效。

new Comparator<File>() {
    @Override
    public int compare(File first, File second) {
        if (first.isDirectory() && second.isDirectory())
            return first.compareTo(second);

        if (first.isDirectory())
            return this.compareToFile(first, second);

        if (second.isDirectory())
            return -(this.compareToFile(second, first));

        return this.compareFiles(first, second);
    }

    private int compareFiles(File first, File second) {
        File firstParentFile = first.getParentFile();
        File secondParentFile = second.getParentFile();

        if (isSubDir(firstParentFile, secondParentFile))
            return -1;

        if (isSubDir(secondParentFile, firstParentFile))
            return 1;

        return first.compareTo(second);
    }

    private int compareToFile(File directory, File file) {
        File fileParent = file.getParentFile();
        if (directory.equals(fileParent))
            return -1;

        if (isSubDir(directory, fileParent))
            return -1;

        return directory.compareTo(file);
    }

    private boolean isSubDir(File directory, File subDir) {
        for (File parentDir = directory.getParentFile(); parentDir != null; parentDir = parentDir.getParentFile()) {
            if (subDir.equals(parentDir)) {
                return true;
            }
        }

        return false;
    }