Java Java.io.File用法及代码示例

// In this Java program, we accepts a file or directory name
// from command line arguments. Then the program will check
// if that file or directory physically exist or not and it
// displays the property of that file or directory.
import java.io.File;
// Displaying file property
class fileProperty {
    public static void main(String[] args)
    {
        // accept file name or directory name through
        // command line args
        String fname = args[0];
        // pass the filename or directory name to File
        // object
        File f = new File(fname);
        // apply File class methods on File object
        System.out.println("File name :" + f.getName());
        System.out.println("Path: " + f.getPath());
        System.out.println("Absolute path:"
                           + f.getAbsolutePath());
        System.out.println("Parent:" + f.getParent());
        System.out.println("Exists :" + f.exists());
        if (f.exists()) {
            System.out.println("Is writable:"
                               + f.canWrite());
            System.out.println("Is readable" + f.canRead());
            System.out.println("Is a directory:"
                               + f.isDirectory());
            System.out.println("File Size in bytes "
                               + f.length());
        }
    }
}

// Java Program to display all
// the contents of a directory
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
// Displaying the contents of a directory
class Contents {
    public static void main(String[] args)
        throws IOException
    {
        // enter the path and dirname from keyboard
        BufferedReader br = new BufferedReader(
            new InputStreamReader(System.in));
        System.out.println("Enter dirpath:");
        String dirpath = br.readLine();
        System.out.println("Enter the dirname");
        String dname = br.readLine();
        // create File object with dirpath and dname
        File f = new File(dirpath, dname);
        // if directory exists,then
        if (f.exists()) {
            // get the contents into arr[]
            // now arr[i] represent either a File or
            // Directory
            String arr[] = f.list();
            // find no. of entries in the directory
            int n = arr.length;
            // displaying the entries
            for (int i = 0; i < n; i++) {
                System.out.println(arr[i]);
                // create File object with the entry and
                // test if it is a file or directory
                File f1 = new File(arr[i]);
                if (f1.isFile())
                    System.out.println(": is a file");
                if (f1.isDirectory())
                    System.out.println(": is a directory");
            }
            System.out.println(
                "No of entries in this directory " + n);
        }
        else
            System.out.println("Directory not found");
    }
}