Initial data commit

Task/Unix-ls/Java/unix-ls-1.java

@@ -0,0 +1,86 @@
+import java.io.File;
+import java.util.ArrayList;
+import java.util.Formatter;
+import java.util.List;
+
+public class Ls {
+    public static void main(String[] args) throws Exception {
+        Ls ls = new Ls("/");
+        System.out.println(ls);
+    }
+
+    private final File directory;
+    private final List<File> list;
+
+    public Ls(String path) throws Exception {
+        directory = new File(path);
+        if (!directory.exists())
+            throw new Exception("Path not found '%s'".formatted(directory));
+        if (!directory.isDirectory())
+            throw new Exception("Not a directory '%s'".formatted(directory));
+        list = new ArrayList<>(List.of(directory.listFiles()));
+        /* place the directories first */
+        list.sort((fileA, fileB) -> {
+            if (fileA.isDirectory() && fileB.isFile()) {
+                return -1;
+            } else if (fileA.isFile() && fileB.isDirectory()) {
+                return 1;
+            }
+            return 0;
+        });
+    }
+
+    private String size(long bytes) {
+        if (bytes > 1E9) {
+            return "%.1fG".formatted(bytes / 1E9d);
+        } else if (bytes > 1E6) {
+            return "%.1fM".formatted(bytes / 1E6d);
+        } else if (bytes > 1E3) {
+            return "%.1fK".formatted(bytes / 1E3d);
+        } else {
+            return "%d".formatted(bytes);
+        }
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder string = new StringBuilder();
+        Formatter formatter = new Formatter(string);
+        /* add parent and current directory listings */
+        list.add(0, directory.getParentFile());
+        list.add(0, directory);
+        /* generate total used space value */
+        long total = 0;
+        for (File file : list) {
+            if (file == null) continue;
+            total += file.length();
+        }
+        formatter.format("total %s%n", size(total));
+        /* generate output for each entry */
+        int index = 0;
+        for (File file : list) {
+            if (file == null) continue;
+            /* generate permission columns */
+            formatter.format(file.isDirectory() ? "d" : "-");
+            formatter.format(file.canRead() ? "r" : "-");
+            formatter.format(file.canWrite() ? "w" : "-");
+            formatter.format(file.canExecute() ? "x" : "-");
+            /* include size */
+            formatter.format("%7s ", size(file.length()));
+            /* modification timestamp */
+            formatter.format("%tb %1$td %1$tR ", file.lastModified());
+            /* file or directory name */
+            switch (index) {
+                case 0 -> formatter.format(".");
+                case 1 -> formatter.format("..");
+                default -> formatter.format("%s", file.getName());
+            }
+            if (file.isDirectory())
+                formatter.format(File.separator);
+            formatter.format("%n");
+            index++;
+        }
+        formatter.flush();
+        return string.toString();
+    }
+}