Use of the file class, common APIs and how to traverse directories and subdirectories

Common APIs

Package Corejava;
Import Java.io.File;

Import java.io.IOException; public class Filedemo {public static void main (string[] args) {//Understand the constructor, check Help file file = new file
        ("G:\\workspace_java\\corejava\\src\\corejava\\test");
        File File2 = new file ("G:" +file.separator);//Separator//system.out.println (file.exists ());
        if (!file.exists ()) File.mkdir ();//file.mkdirs ();//Multilevel Directory else File.delete ();
        is a directory System.out.println (File.isdirectory ());

        Whether it is a file System.out.println (File.isfile ());
        File File2 = new file ("G:\\workspace_java\\corejava\\src\\corejava\\test.txt");
        File File2 = new file ("G:\\workspace_java\\corejava\\src\\corejava", "test.txt");
            if (!file2.exists ()) try {file2.createnewfile ();
            catch (IOException e) {//TODO auto-generated catch block E.printstacktrace ();
   }     else File2.delete (); The common file object's API System.out.println (file),//file.tostring () content System.out.println (File.getabsolutepath ());
        /abstract Path System.out.println (File.getname ());//The name of the file System.out.println (File2.getname ());
        System.out.println (File.getparent ());
        System.out.println (File2.getparent ());

    System.out.println (File.getparentfile (). GetAbsolutePath ());
 }

}

Run results

True
false
G:\workspace_JAVA\coreJava\src\coreJava\test
G:\workspace_JAVA\coreJava\src\coreJava\ Test
Test
test.txt
G:\workspace_JAVA\coreJava\src\coreJava
G:\workspace_JAVA\coreJava\src\ Corejava
G:\workspace_JAVA\coreJava\src\coreJava

Traverse Directory

Package Corejava;
Import Java.io.File;

Import java.io.IOException; public class FileUtils {/** * lists all files in the specified directory (including its subdirectories) * @param args/public static void Listdirect Ory (File dir) throws ioexception{//TODO auto-generated Method stub if (!dir.exists ()) {throw
        New IllegalArgumentException ("Directory: +dir+" does not exist. ");}
        if (!dir.isdirectory ()) {throw new IllegalArgumentException (dir+ "not Directory");
            }/*string[] filenames = dir.list ()//Returns a string array, the name of the direct child, and does not contain the contents of the subdirectory for (String string:filenames) {
        System.out.println (dir+ "\" +string);
        }*///If you want to traverse the contents of the subdirectory, you need to construct a file object to do the recursive operation, file provides an abstract file[that directly returns the subdirectory] files = Dir.listfiles (); Direct subdirectories (Abstract of the file) are returned directly. if (files!=null&&files.length>0) {for (File file:files) {if (file.isdirect
                Ory ()) {//recursive listdirectory (file);
    } else{                System.out.println (file);
 }
            }
        }
    }

}

Test method

Package Corejava;

Import Java.io.File;
Import java.io.IOException;

public class Test1 {public

    static void Main (string[] args) throws IOException {
        //TODO auto-generated method Stu b
        Fileutils.listdirectory (New File ("G:\\workspace_java"));
    }

Run results

g:\workspace_java\.metadata\.plugins\org.eclipse.pde.core\eclipse Application\ Org.eclipse.osgi\899\0\.cp\icons\wtp_icon_x32.gif G:\workspace_JAVA\.metadata\.plugins\org.eclipse.pde.core\ Eclipse Application\org.eclipse.osgi\899\0\.cp\icons\wtp_icon_x48.gif G:\workspace_JAVA\.metadata\.plugins\ Org.eclipse.pde.core\eclipse application\org.eclipse.osgi\899\0\.cp\images\01.png G:\workspace_JAVA\.metadata\. Plugins\org.eclipse.pde.core\eclipse application\org.eclipse.osgi\899\0\.cp\images\02a.png G:\workspace_JAVA\. Metadata\.plugins\org.eclipse.pde.core\eclipse Application\org.eclipse.osgi\899\0\.cp\images\02b.png G:\ Workspace_java\.metadata\.plugins\org.eclipse.pde.core\eclipse application\org.eclipse.osgi\899\0\.cp\images\ 02b_o.png G:\workspace_JAVA\.metadata\.plugins\org.eclipse.pde.core\Eclipse application\org.eclipse.osgi\899\0\. Cp\images\02c.png