java gets the code for a known file extension

1. Demand analysis

1, get known file extensions -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- - "to read the file first, get the file name
2, abc.txt extension is txt, abc.Java

2. Technical Difficulties

1. Convert 1 given path into 1 file object and get the complete file name

You can do this directly with the new File() class, and then get the file name from getName

2. How to get the extension through the file name?

This can be obtained by splitting the file names into regular expressions

Code implementation :(PS adds a function that gives the file extension under the specified directory to get the loop directory)

package com.itheima;

import java.io.File;

/**
 * 7 ,   Write a program to get the extension of a known file .  Pay attention to : abc.txt The extension is txt, abc.java.txt The extension is also txt.
 * 
 * @author 281167413@qq.com
 */

public class Test7 {

	public static void main(String[] args) {
		String srcPath = "D:/java/java.copy.doc";

		getFilenameExtension(srcPath);
	}

	//  Gets the extension of the specified file 
	public static void getFilenameExtension(String srcPath) {
		//  Converts the source path to a file object 
		File file = new File(srcPath);

		if (file.isFile()) {
			String name = file.getName();

			String[] exName = name.split("\\.");

			System.out.println(exName[exName.length - 1]);
		} else {
			System.out.println("It's not a file!");
		}
	}

	//  Gets the extension of the file in the specified directory 
	public static void getDirFilenameExtension(String srcPath) {
		//  Converts the source path to the directory object 
		File[] file = (new File(srcPath)).listFiles();
		for (int i = 0; i < file.length; i++) {
			if (file[i].isDirectory()) {
				//  Source folder ready to be copied 
				srcPath = srcPath + "/" + file[i].getName();
				getDirFilenameExtension(srcPath);
			} else {
				//  The source file 
				File sourceFile = file[i];
				//  The file name 
				String name = sourceFile.getName();

				String[] exName = name.split("\\.");

				System.out.println(exName[exName.length - 1]);
			}
		}
	}
}

For more details, please refer to previous articles published on this site.