This is a File Browser program that can be used to locate, append, and display files, also has an option of creating a log file that updates and prints everything that is shown to the user. Option (4) is the one thing I can't get working at the moment but it doesn't crash the program.

FileBrowser.java

import java.util.Scanner;
import java.io.*;

public class FileBrowser{

	private static String logName;

	public FileBrowser(){
		logFile();
		run();
	}

	public static void print(String s){
		updateLog(s);
		System.out.println(s);
	}

	// public void listOptions(){ wanted to make this a seperate method but had to make run() a static method and couldnt have this as a non-static
	// 	print("File Browser 9000");
	// 	print(" ");
	// 	print("(1) List the contents of a directory.");
	// 	print("(2) List the contents and sub directories of a directory.");
	// 	print("(3) Locate a file with a given name.");
	// 	print("(4) Locate files with a given file extension.");
	// 	print("(5) Concatenate the contents of 2 files and output the result to a third file.");
	// 	print("(6) Exit");
	// }

	public static void run(){
		Scanner input = new Scanner(System.in);
		print("File Browser 9000");
		print(" ");
		print("(1) List the contents of a directory.");
		print("(2) List the contents and sub directories of a directory.");
		print("(3) Locate a file with a given name.");
		print("(4) Locate files with a given file extension.");
		print("(5) Concatenate the contents of 2 files and output the result to a third file.");
		print("(6) Exit");
		String answer = input.nextLine();
		updateLog(answer);
		if(answer.equals("1")){
			ListContents listContents = new ListContents(1);
		}
		else if (answer.equals("2")){
			ListContents listContents = new ListContents(2);
		}
		else if(answer.equals("3")){
			LocateFile locateFile = new LocateFile(3);
		}
		else if(answer.equals("4")){
			LocateFile locateFile = new LocateFile(4);
		}
		else if(answer.equals("5")){
			LocateFile locateFile = new LocateFile(5);
		}
		else if (answer.equals("6")){
			System.exit(1);//quits program
		}
	}

		public void logFile(){
		Scanner input = new Scanner(System.in);
		System.out.println("Would you like to make a log[Yes/No]: ");
		if(input.nextLine().equalsIgnoreCase("yes")){
			System.out.println("Name the log file(ex: log.txt): ");
			logName = input.nextLine();
			try{
				PrintWriter pw = new PrintWriter(new FileOutputStream(logName));
				pw.close();
			}
			catch(Exception ex){
				System.out.println("Exception " + ex.getMessage());
			}
		}
	}

		public static void updateLog(String records){ //updates log, static to use in other classes to update and not create an object each time
			if(logName == null){
				return;
			}
		try{
			PrintWriter pw = new PrintWriter(new FileOutputStream(logName, true));
			pw.println(records);
			pw.close();
		}
		catch(Exception ex){
			System.out.println("Exception " + ex.getMessage());
		}
	}

	public static void main(String[] args){
		FileBrowser fileBrowser = new FileBrowser();
	}
}

ListContents.java

import java.util.Scanner;
import java.io.*;

public class ListContents{

	public ListContents(int i){
		Scanner input = new Scanner(System.in);
		File directory;
		while(true){//repeats incase user enters a directory that doesnt exist
			FileBrowser.print("Enter Directory: ");
			String answer = input.nextLine();
			FileBrowser.updateLog(answer);
			directory = new File(answer);
			if(directory.listFiles() != null){
				break;
			}
		}
		if(i == 1){ //shows files only
			try{
				//FileBrowser.print("Before showDirectory"); used to check for errors
				showDirectory(directory.listFiles());//array of Files sent to method
			}
			catch(Exception ex){
				FileBrowser.print("Exception " + ex.getMessage());
			}
		}else if(i == 2){//shows files and subdirectories
			try{
				printTree(directory);//array of Files sent to method
			}
			catch(Exception ex){
				FileBrowser.print("Exception " + ex.getMessage());
			}
		}
		FileBrowser.run();
	}

	public void showDirectory(File[] files){ //prints directory
		//FileBrowser.print("showDirectory");used to check for errors
		try{
		for(int i = 0; i < files.length; ++i){
			FileBrowser.print(files[i].getName());
		}
		System.out.println();
		}
		// catch(FileNotFound fx){
		// 	FileBrowser.print(fx.getMessage());
		// }
		catch(Exception ex){
			FileBrowser.print("Exception " + ex.getMessage());
		}
		FileBrowser.print(" ");
		
	}

	public void printTree(File f){//using recursion for printing out list of files and the subdirectories	
		//FileBrowser.print("printTree");used to check for errors
		File[] theFiles = f.listFiles();
		for(int i = 0; i < theFiles.length; ++i){
			if(!(theFiles[i].isDirectory())){
				try{
					FileBrowser.print(theFiles[i].getName());	
				}
				catch(Exception ex){
					FileBrowser.print("Exception " + ex.getMessage());
				}
			}
			else{
				try{
					FileBrowser.print(theFiles[i].getName());
					printTree(theFiles[i]);
				}
				catch(Exception ex){
					FileBrowser.print("Exception " + ex.getMessage());
				}	
			}
		}
			FileBrowser.print(" ");
	}
}

LocateFile.java

import java.util.Scanner;
import java.io.*;

public class LocateFile{


	private boolean fileFound;
	private String fileExtension;

	public LocateFile(int i){
		this.fileFound = false;
		if(i == 3){
			FileBrowser.print("Enter file name: ");
			searchComputer(false);
		}
		else if(i == 4){
			FileBrowser.print("Enter file extention (ex: txt\\java\\jpg): ");
			searchComputer(true);
		}
		else if(i == 5){
			concatenateFiles();
		}
		FileBrowser.run();
	}

	// public void searchFile(){
	// 	Scanner input = new Scanner(System.in);
	// 	FileBrowser.print("Enter file name: ");
	// 	String fileName = input.nextLine();
	// 	try{

	// 	}
	// 	catch(Exception ex){
	// 		FileBrowser.print(ex.getMessage());
	// 	}
	// }


	public void searchComputer(boolean filter){
		Scanner input = new Scanner(System.in);
		this.fileExtension = input.nextLine();
		FileBrowser.print("Searching...");		
		FileBrowser.print(" ");
		searchDirectory(this.fileExtension, (new File("\\")), filter);
	}

	public void searchDirectory(String fileName, File f, boolean extention){
		File[] theFiles = f.listFiles();
		if(!this.fileFound){
			for(int i = 0; i < theFiles.length; ++i){
				if(!extention){
					if(theFiles[i].getName().equals(fileName)){
						try{
							this.fileFound = true;
							FileBrowser.print(theFiles[i].getPath());
						}
						catch(Exception ex){
							// FileBrowser.print(("Exception: " + ex.getMessage()));
						}
					}
				}else{
					String chars = theFiles[i].getName();
					if(theFiles[i].getName().substring(theFiles[i].getName().length() - chars.length(), theFiles[i].getName().length()).equals(fileName) && !theFiles[i].isDirectory()){
						try{
							FileBrowser.print(theFiles[i].getName());
							FileBrowser.print(theFiles[i].getPath());
						}
						catch(Exception ex){
							// FileBrowser.print("Exception: " + ex.getMessage());
						}
					}
				}
			}
			for (int i = 0; i < theFiles.length; ++i) {
				if(theFiles[i].isDirectory() && !this.fileFound || extention){ //goes to next directory to search for file
					try{
						searchDirectory(fileName, theFiles[i], extention);
					}
					 catch(Exception ex){
					 	// FileBrowser.print("Exception: " + ex.getMessage());
					 }	
				}
			}

		}
	}

	public void concatenateFiles(){
		Scanner input = new Scanner(System.in);
		FileBrowser.print("Enter Full Pathnames that are given in option (4)");
		FileBrowser.print("Path of 1st File: ");
		String firstFile = input.nextLine();
		FileBrowser.print("Path of 2nd File: ");
		String secondFile = input.nextLine();
		String temp1 = " ";
		String temp2 = " ";
		try{
			Scanner sc1 = new Scanner(new FileInputStream(firstFile));
			while(sc1.hasNextLine()){
			temp1 += sc1.nextLine();
			}
			sc1.close();
			Scanner sc2 = new Scanner(new FileInputStream(secondFile));
			while(sc2.hasNextLine()){
			temp2 += sc2.nextLine();
			}
			sc2.close();
		}
		catch(Exception fx){
			FileBrowser.print(fx.getMessage());
		}	
		FileBrowser.print("Name of new file?(Add \".txt\" extension): ");
		String newFile = input.nextLine();
		try{
			PrintWriter pw = new PrintWriter(new FileOutputStream(newFile));
			pw.write(temp1 + " " + temp2);
			pw.close();
		}
		catch(Exception fx){
			FileBrowser.print(fx.getMessage());
		}
	}
}