스레드 관련되어서 질문드립니다.... 제발부탁드립니다..

소스코드내용
 
import java.io.*;
import java.net.*;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets; 
import java.nio.file.Files;
import java.nio.file.Paths; 
 
 
class Server1 {  
 
 
	public static class AndroidServer extends Server1 implements Runnable{
		public static final int serverPort = 10200;
		@Override
		public void run(){
			try{
				System.out.println("----------------------------");
				System.out.println("AndoridServer 동작중입니다...");  
				System.out.println("----------------------------");
 
				while(true)
				{
				ServerSocket serverSocket = new ServerSocket(serverPort);
				Socket sock = serverSocket.accept();
				System.out.println("AndroidClient 접속하였습니다.");
				try{
					BufferedReader in = new BufferedReader(new InputStreamReader(sock.getInputStream()));
					String str = in.readLine();
					System.out.println("수신중인 파일 이름 : " + str);
					File f1 = new File("c:\\Temp", str);
					FileOutputStream output = new FileOutputStream(f1);
					byte[] buf = new byte[1024];
					while(sock.getInputStream().read(buf)>0){
						output.write(buf);
						output.flush();
					}
					in.close();
					output.close();
					System.out.println(str + ".std 수신완료");
					String s1 = readFile(f1.getAbsolutePath(), StandardCharsets.UTF_8);
				}catch(Exception e){
					System.out.println("서버에러");
					e.printStackTrace();
				}finally{
					}
				}
			}catch(IOException e)
				{
					e.printStackTrace();
				}
			}
 
		static String readFile(String path, Charset encoding)throws IOException {     
					byte[] encoded = Files.readAllBytes(Paths.get(path));
					System.out.println("올바른 파일을 선택하여주세요.");
					return encoding.decode(ByteBuffer.wrap(encoded)).toString();
					}
 
 
	public static class WindowServer extends Server1 implements Runnable{
		public static final int serverPort = 5555;
		@Override
		public void run(){
			try{
				System.out.println("----------------------------");
				System.out.println("WindowServer 동작중입니다...");  
				System.out.println("----------------------------");
 
				ServerSocket server = new ServerSocket(serverPort);
				Socket sk = server.accept();
				System.out.println("Window Client 접속하였습니다.");
				try{
					InputStream input = sk.getInputStream();   
					BufferedReader inReader = new BufferedReader
							(new InputStreamReader(sk.getInputStream())); 
					BufferedWriter outReader = new BufferedWriter
							(new OutputStreamWriter(sk.getOutputStream()));
					// Read the filename     
					String filename = inReader.readLine(); 
					System.out.println("수신중인 파일 이름 : " + filename);
					File f3 = new File("C://tmp/", filename);      
					if(!f3.isDirectory()) {       
						f3.mkdir();    
						}  
					FileOutputStream wr = new FileOutputStream(new File("C://tmp/" + filename));
					byte[] buffer = new byte[sk.getReceiveBufferSize()];
					int bytesReceived = 0;           
					while((bytesReceived = input.read(buffer))>0)  
					{            
						// Write to the file 
						wr.write(buffer,0,bytesReceived); 
						}                  
					File f2 = new File("C://tmp/" + filename);  
					String s2 = readFile(f2.getAbsolutePath(), StandardCharsets.UTF_8);
				}catch(Exception e){
			}finally{
				}
			}catch(IOException e){
				e.printStackTrace();
				}
			}
 
 
		static String readFile(String path, Charset encoding)throws IOException {     
					byte[] encoded = Files.readAllBytes(Paths.get(path));
					System.out.println("올바른 파일을 선택하여주세요.");
					return encoding.decode(ByteBuffer.wrap(encoded)).toString();
					}
 
		}
 
	public static class Prepare extends Server1 implements Runnable{
		@Override
		public void run(){
 
			try{
 
			}catch(Exception e){
				e.printStackTrace();
			}
		}
	}
	public static void main(String args[])throws Exception {
		File f1;
		File f2;
 
		Thread as = new Thread(new AndroidServer());
		as.setName("AndroidServer");
		Thread ws = new Thread(new WindowServer());
		ws.setName("WindowServer");
		Thread pp = new Thread(new Prepare());
		pp.setName("Prepare");
		as.start();
		ws.start();
		pp.start();
		}
	}
	}