Getting number of lines in a file

The following code 'll return the number of lines in the file 'example.txt'

1. public static int getNoOfLines(String filename){
2.   File file = new File("example.txt");
3.   if (!file.exists()){
4.    System.out.println("File doesn't exist");
5.    System.exit(0);
6.   }
7.   if (file.isDirectory()){
8.    System.out.println("Expected file name but entered directory name");
9.    System.exit(0);
10.   }
11.   int line = 0;
12.   try {
13.     LineNumberReader ln = new LineNumberReader(new FileReader(filename));                                                                        
14.           while (ln.readLine() != null) {
15.            line++;
16.           }
17.       } catch (IOException e) {
18.        e.printStackTrace();
19.       }
20.   return line;  
21.  }

Checking a file/directory present or not

The following code 'll return boolean values,true if the file/directory is present,false if the file/directory is not present.

1. public boolean isFileOrDirectoryPresent(String fileOrDirName){
2.   File file = new File(fileOrDirName);
3.   if (!file.exists()){
4.     System.out.println("File/Directory doesn't exist");
5.     return false;
6.   }
7.   else {
8.     System.out.println("File/Directory exists");
9.     return true;
10.   }
11. }

Getting list of files/subdirectories in a directory

The following code 'll return the list of files that are present in the directory.This function accepts a parameter 'dirName',the directory in which you want the list of files.

1. public String[] filesInDir(String dirName){
2.   String[] files = null;  
3.   try {
4.     File dir = new File(dirName);
5.     if (dir.isDirectory()) {
6.       files = dir.list();
7.     }
8.     else if (!dir.exists()){
9.       System.out.println("Directory doesn't exist");
10.       System.exit(0);
11.    }
12.    } catch (Exception e) {
13.      e.printStackTrace();
14.    }  
15.   return files;
16. }

Copy directory in Java

The following code 'll copy the contents of a given source folder to a given destination folder.This method accepts 2 parameters,one for source folder location and another for destination folder location.

1. public static void copyFolder(File srcFolder, File destFolder)  
   throws IOException{
2.  
3.  if(!srcFolder.exists()){
4.     System.out.println("Source folder does not exist!");
5.     System.exit(0);
6.  }
7.      
8. //If folder/directory
9.  if(srcFolder.isDirectory()){  
10.  
11.   //If destination directory doesn't exist, create it
12.   if(!destFolder.exists()){
13.      destFolder.mkdir();
14.   }
15.  
16.   //List all the contents of source directory
17.   String files[] = srcFolder.list();
18.   for (String file : files) {
19.      //construct the srcFolder and destFolder file structure
20.      File srcFile = new File(srcFolder, file);
21.      File destFile = new File(destFolder, file);
22.  
23.      //recursive copy
24.      copyFolder(srcFile,destFile);
25.   }
26.  }
27.  
28.  //If file, then copy it
29.  else{
30.  
31.  //Use bytes stream to support all file types
32.   InputStream in = new FileInputStream(srcFolder);
33.   OutputStream out = new FileOutputStream(destFolder);
34.      byte[] buffer = new byte[1024];
35.      int length;
36.      
37.      //copy the file content in bytes
38.      while ((length = in.read(buffer)) > 0){
39.      out.write(buffer, 0, length);
40.      }
41.      in.close();
42.      out.close();
43.  }
44. }