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The SizeFileComparator class in the ApacheSW Commons IOS library has several Comparator singletons for sorting files according to file size. Files can be sorted in ascending and descending size order. SIZE_COMPARATOR and SIZE_REVERSE treat directory sizes as 0, while SIZE_SUMDIR_COMPARATOR and SIZE_SUMDIR_REVERSE treat directory sizes as the sum of their contents. The SizeFileComparatorTest class demonstrates this.

SizeFileComparatorTest.java

package test;

import java.io.File;
import java.io.IOException;
import java.util.Arrays;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.comparator.SizeFileComparator;

public class SizeFileComparatorTest {

	public static void main(String[] args) throws IOException {
		File directory = new File(".");
		File[] files = directory.listFiles();

		System.out.println("Default order");
		displayFiles(files);

		Arrays.sort(files, SizeFileComparator.SIZE_COMPARATOR);
		System.out.println("\nSizeFileComparator.SIZE_COMPARATOR (Ascending, directories treated as 0)");
		displayFiles(files);

		Arrays.sort(files, SizeFileComparator.SIZE_REVERSE);
		System.out.println("\nSizeFileComparator.SIZE_REVERSE (Descending, directories treated as 0)");
		displayFiles(files);

		Arrays.sort(files, SizeFileComparator.SIZE_SUMDIR_COMPARATOR);
		System.out.println("\nSizeFileComparator.SIZE_SUMDIR_COMPARATOR (Ascending, directory size used)");
		displayFilesWithDirectorySizes(files);

		Arrays.sort(files, SizeFileComparator.SIZE_SUMDIR_REVERSE);
		System.out.println("\nSizeFileComparator.SIZE_SUMDIR_REVERSE (Descending, directory size used)");
		displayFilesWithDirectorySizes(files);
	}

	public static void displayFiles(File[] files) {
		for (File file : files) {
			System.out.printf("%-20s Size:" + file.length() + "\n", file.getName());
		}
	}

	public static void displayFilesWithDirectorySizes(File[] files) {
		for (File file : files) {
			if (file.isDirectory()) {
				System.out.printf("%-20s Size:" + FileUtils.sizeOfDirectory(file) + "\n", file.getName());
			} else {
				System.out.printf("%-20s Size:" + file.length() + "\n", file.getName());
			}
		}
	}

}

The console output from the execution of SizeFileComparatorTest is self-explanatory and shown below:

Results

Default order
.classpath           Size:293
.project             Size:383
bin                  Size:0
docs                 Size:0
lib                  Size:0
src                  Size:0
Test1.txt            Size:17
test2.txt            Size:19
Test3.txt            Size:11
test4.txt            Size:19

SizeFileComparator.SIZE_COMPARATOR (Ascending, directories treated as 0)
bin                  Size:0
docs                 Size:0
lib                  Size:0
src                  Size:0
Test3.txt            Size:11
Test1.txt            Size:17
test2.txt            Size:19
test4.txt            Size:19
.classpath           Size:293
.project             Size:383

SizeFileComparator.SIZE_REVERSE (Descending, directories treated as 0)
.project             Size:383
.classpath           Size:293
test2.txt            Size:19
test4.txt            Size:19
Test1.txt            Size:17
Test3.txt            Size:11
bin                  Size:0
docs                 Size:0
lib                  Size:0
src                  Size:0

SizeFileComparator.SIZE_SUMDIR_COMPARATOR (Ascending, directory size used)
Test3.txt            Size:11
Test1.txt            Size:17
test2.txt            Size:19
test4.txt            Size:19
.classpath           Size:293
.project             Size:383
src                  Size:3513
bin                  Size:5417
lib                  Size:289835
docs                 Size:529577544

SizeFileComparator.SIZE_SUMDIR_REVERSE (Descending, directory size used)
docs                 Size:529577544
lib                  Size:289835
bin                  Size:5417
src                  Size:3513
.project             Size:383
.classpath           Size:293
test2.txt            Size:19
test4.txt            Size:19
Test1.txt            Size:17
Test3.txt            Size:11