Files

[Adam Chalkley]

hi guys I keep getting a nullPointerException and I can't figure out why?

my directory contains 4 files and 3 directories

import java.io.File;


public class Main {

	public static StringBuilder builder = new StringBuilder();
	
	public static void main(String[] args) {
		
		String path = ("C:\\Users\\College\\workspace\\AdventureGameTWO");
		listAllFiles(path);
        
	}

	public static void listAllFiles(String path){
		
		File f = new File(path);
		
		
		
		if(f.isFile()){
			
			builder.append(f.getName());
			
		}
		
		for(String s: f.list()){
			
			System.out.println(s);
			listAllFiles(s);
			
			
		}
		
	}
	
}

then I changed the code a little to make sure the file is a directory so maybe I wouldn't get a nullPointer exception it worked no exceptions but the only problem is that it does not actually print the files

import java.io.File;


public class Main {

	public static StringBuilder builder = new StringBuilder();
	
	public static void main(String[] args) {
		
		String path = ("C:\\Users\\College\\workspace\\AdventureGameTWO");
		listAllFiles(path);
        
	}

	public static void listAllFiles(String path){
		
		File f = new File(path);
		
		
		
		if(f.isFile()){
			
			builder.append(f.getName());
			
		}
		
		for(String s: f.list()){
			
			File file = new File("C:\\Users\\College\\workspace\\AdventureGameTWO\\" + s);
			
			if(file.isDirectory()){
			listAllFiles(s);
			
			}
			
		}

any ideas how I can get this code working to actually print the file names?

thanks

[Adam Chalkley]

I found a way to list all the directories in my workspace

but I still need to figure out a way to print the files in those directories

import java.io.File;

public class Main {
	
	public static void main(String[] args){
		
		File file = new File("C:\\Users\\College\\workspace");
		list(file);
		
	}
	
	public static void list(File f){
	
	System.out.println(f.getName());
	File[] files = f.listFiles();
	
	  for(File file : files){
		  
		  if(file.isFile()){
			  
		  }
		  
		  if(file.isDirectory()){
		  list(file);
		  
		  }
		  
	  }
	
	}

}

[Adam Chalkley]

Ok guys I figured out the solution,feedback is more than welcome


thanks

[Tony Docherty]

Well done for figuring it out. Show us your solution and we will give you some feedback.

[Adam Chalkley]

sorry forgot to post the solution

import java.io.File;

public class Main {
	
	public static void main(String[] args){
		
		File file = new File("C:\\Users\\Adam\\workspace\\AdventureGameTWO");
		list(file);
		
	}
	
	
	
	public static void list(File f){
	
	System.out.println(f.getName());
	File[] files = f.listFiles();
	
	  for(File file : files){
		  
		  if(file.isFile()){
			  System.out.println("FILE" + file.getName());
		  }
		  
		  if(file.isDirectory()){
		  list(file);
		  
		  }
	  }
	
	}

}

[Campbell Ritchie]

I don't like your making both methods static. Yes, you have to start off in a static method (main) but you shou‍ld get out of a static context as soon as possible. Since you are not creating any objects, that isn't an object‑oriented approach.

In the case of listing files, you can argue that you you won't notice the difference between the results from an object‑oriented (=OO) solution and a procedural solution, but you shou‍ld probably get into the habit of writing OO as soon as possible.

[Adam Chalkley]

thanks Campbell great tips, I'll keep them in mind =)

[Carey Brown]

This is a slight reorganization of your solution but this will handle the case where the parameter 'f' could be a file or a directory.

	public static void list( File f )
	{
		if( f.isFile() )
		{
			System.out.println( "FILE: " + f.getName() );
		}
		else if( f.isDirectory() )
		{
			File[] files = f.listFiles();
			for( File file : files )
			{
				list( file );
			}
		}
	}