File Path, File Name and Extension Program in Java and Python

Question:

Algorithm:

Explanation:

The full file path contains three useful parts: the folder path, the file name and the file extension. In a path such as C:Users\admin\Pictures\flowers.jpg, the last backslash separates the folder path from the actual file name. The last full stop separates the file name from the extension. Therefore the program does not need to check every folder separately. It only needs to locate these two important positions.

The method lastIndexOf('\\') is used to find the final backslash in the string. In Java, a backslash is written as '\\' because the backslash is an escape character. A single backslash is used inside strings and character literals to give special meanings to characters, such as newline. To represent the actual backslash character, it must be escaped with another backslash. The index returned by this method is stored in x.

Similarly, lastIndexOf('.') gives the position of the final dot in the file path. This is stored in y. The final dot is used because file names may sometimes contain other dots before the extension. Once the positions are known, substring() is used to extract the required parts. The path is the part before the last backslash. The file name starts just after the last backslash and ends just before the final dot. The extension starts just after the final dot and continues up to the end of the string.

For example, in C:Users\Java\awesome.txt, the last backslash is before awesome and the final dot is before txt. So the path becomes C:Users\Java, the file name becomes awesome and the extension becomes txt. This approach is short and clear because it uses built-in string library functions rather than manually counting characters.

Java Program:

/**
* The class File_Q6_ICSE2014 inputs the full path of a file and
* outputs the file path, file name and file extension separately.
* @author : www.guideforschool.com
* @Program Type : BlueJ Program - Java
* @Question Year : ICSE 2014 Question 6
*/

import java.util.Scanner;

class File_Q6_ICSE2014
{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter the full path of the file : ");
        String s = sc.nextLine();

        // Find the last backslash and the last dot in the file path.
        int x = s.lastIndexOf('\\');
        int y = s.lastIndexOf('.');

        String path = s.substring(0, x);
        String file = s.substring(x + 1, y);
        String extn = s.substring(y + 1);

        System.out.println("Output :");
        System.out.println("Path : " + path);
        System.out.println("File Name : " + file);
        System.out.println("Extension : " + extn);
    }
}

Equivalent Python Program:

# Program to extract file path, file name and extension
# from a complete file path.

full_path = input("Enter the full path of the file : ")

# Find the last backslash and the last dot.
x = full_path.rfind("\\")
y = full_path.rfind(".")

path = full_path[:x]
file_name = full_path[x + 1:y]
extension = full_path[y + 1:]

print("Output :")
print("Path :", path)
print("File Name :", file_name)
print("Extension :", extension)

Output: