Complete code for file traversal in the background folder of Java

There are two ways to traverse all files in a folder in Java:

1Recursive traversal is usually the first method that developers can think of, the advantages of recursive traversal are: relatively simple implementation, less code, and higher execution efficiency, but the disadvantages are: relatively high memory consumption, and higher hardware requirements

// Recursive traversal
 private void getDirectory(File file) {
 File flist[] = file.listFiles();
 if (flist == null || flist.length == 0) {
   return 0;
 }
 for (File f : flist) {
   if (f.isDirectory()) {
     //All folders will be listed here
     System.out.println("Dir==>" + f.getAbsolutePath()); 
     getDirectory(f);
   } else {
     //All files will be listed here
     System.out.println("file==>" + f.getAbsolutePath());
   }
 }
}

2Non-recursive traversal is relatively easy to understand, but non-recursive traversal may not be easy to come up with at first, I also struggled for a long time, and found that Java has a LinkedList thing, which is also roughly known, it is used to save a list of linked files, if there is one, it is convenient to deal with it, the specific idea is like this: when traversing a folder, if it is a folder, it is added to the LinkedList, and if it is a file, it is listed; this way, all files and folders in the directory are traversed, and all folders are saved to the LinkedList; so the remaining task is to traverse the files in the folders in the LinkedList, the traversal method is the same as the above operation, if it is a folder, it is added to the LinkedList (Ps: the LinkedList in the traversal process is always the same list), of course, after taking a folder from the list, it needs to be deleted from the list. Here, LinkedList.removeFirst() is used to read, which means reading the first element from the list and removing it from the list. Only when the state of the LinkedList is isEmty does it mean that the traversal is complete.

// Non-recursive traversal
private void GetDirectorySize(File file) {
	LinkedList list = new LinkedList();
	//Save the list of folders to be traversed
	GetOneDir(file, list);
	//Call the method to traverse files under the root directory of the folder
	File tmp;
	while (!list.isEmpty()) {
		tmp = (File) list.removeFirst();
		//The judgment here is a bit redundant, but for safety, a judgment is still given, normally the list only contains folders
		//However, it does not exclude special cases, such as: the target itself is a folder, which has become a file after being pushed onto the stack
		if (tmp.isDirectory()) {
			GetOneDirSize(tmp, list);
		} else {
			System.out.println("file==>" + tmp.getAbsolutePath());
		}
	}
}
// Traverse files under the root directory of the specified folder
private void GetOneDir(File file , LinkedList list){
	//This method is called every time a folder is traversed
	System.out.println("Dir==>" + f.getAbsolutePath());
	File[] files = file.listFiles();
	sumdir += 1;
	if (files == null || files.length == 0) {
		return ;
	}
	for (File f : files) {
		if (f.isDirectory()) {
			list.add(f);
		} else {
			//Here is a list of all files under the root directory of the current folder
			System.out.println("file==>" + f.getAbsolutePath());
		}
	}
}

Section 2: Traverse a folder using Java and get all its contents

package demo0;823;
import java.io.File;
import java.util.ArrayList;
public class FileTest {
	private static ArrayList<String> fileList = new ArrayList<String>();
	public static void main(String[] args) {}}
		String filepath = "G:\\Test\\icon";
		getFiles(filepath);
	}
	static void getFiles(String filepath){
		File root = new File(filepath);
		File[] files = root.listFiles();
		for (File file : files){
			if(file.isDirectory()){
				//If file is a directory, loop and recursively call the cabinet
				//Recursive call
				getFiles(file.getAbsolutePath());
				fileList.add(file.getAbsolutePath());
				System.out.println("Display"+filepath+"all subdirectories and their files"+file.getAbsolutePath());
			}
				//if it is not a directory, traverse its underlying files
				System.out.println("Display"+filepath+"all subfiles"+file.getAbsolutePath());
			}
		}
	}
}

Illustration:

Summary

This is the complete code for traversing files under the Java background folder in this article. I hope it will be helpful to everyone. Those who are interested can continue to read other related topics on this site. If there are any shortcomings, please leave a message to point them out. Thank you for your support to this site!

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