import java.net.Socket;    
import java.io.InputStreamReader;    
import java.io.OutputStreamWriter;      
import java.io.BufferedReader;    
import java.util.ArrayList;      
import java.util.HashMap;     
   
class Program {      
       
    public static void main(String[] args){        
        POP3 popClient = new POP3("pop.host.com", 110);    
        popClient.setCredentials("username", "password");    
            
        System.out.println("Message count: " + popClient.getMessageCount());    
        System.out.println("First message:");    
            
        POP3Message message = popClient.getMessage(1);    
            
        System.out.println("From: " + message.getFrom());    
        System.out.println("To: " + message.getTo());    
        System.out.println("Subject: " + message.getSubject());    
        System.out.println("Date: " + message.getDate());    
        System.out.println("Message: " + message.getBody());    
    }      
}     
   
class POP3{    
   
    protected Socket socket;    
    protected BufferedReader reader;    
    protected OutputStreamWriter writer;    
    protected ArrayList<String> log = new ArrayList<String>();    
        
    public POP3(String host, int port){    
        try{    
            socket = new Socket(host, port);    
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));    
            writer = new OutputStreamWriter(socket.getOutputStream());    
                
            log.add(reader.readLine());    
        }catch(Exception e){    
            log.add(e.getMessage());    
        }    
    }    
        
    public void setCredentials(String username, String password){    
        try{    
            writer.write("USER " + username + "\n");    
            writer.flush();    
            log.add(reader.readLine());     
            writer.write("PASS " + password + "\n");    
            writer.flush();    
                
            log.add(reader.readLine());    
        }catch(Exception ioe){    
            log.add(ioe.getMessage());    
        }    
    }    
        
    public POP3Message getMessage(int msgIndex){    
        
        POP3Message message = new POP3Message();    
            
        try{    
            writer.write("RETR " + Integer.toString(msgIndex) + "\n");    
            writer.flush();    
                
            HashMap<String, String> headerMap = new HashMap<String, String>();    
            boolean headers = true;    
            String response = "";    
            String body = "";    
   
            while(true){    
                response = reader.readLine();     
   
                if (response.trim().equals(".")){      
                    break;      
                }      
                    
                if(response.trim().length() !=0 && headers){    
                    String[] parts = response.split(":", 2);    
                    try{    
                        headerMap.put(parts[0].trim(), parts[1].trim());    
                    }catch(Exception e){    
                    }    
                }else{    
                    headers = false;    
                }    
                    
                if(headers == false){    
                    body +=response;    
                }    
            }    
                
            message.setFrom(headerMap.get("From"));    
            message.setTo(headerMap.get("To"));    
            message.setSubject(headerMap.get("Subject"));    
            message.setDate(headerMap.get("Date"));    
            message.setBody(body);    
                
        }catch(Exception ioe){    
            log.add(ioe.getMessage());    
        }    
        return message;    
    }    
   
    public int getMessageCount(){    
        try{    
            writer.write("STAT\n");    
            writer.flush();    
            String[] parts = reader.readLine().split(" ");    
            return Integer.parseInt(parts[1]);    
        }catch(Exception ioe){    
            log.add(ioe.getMessage());    
        }    
        return 0;    
    }    
        
    public ArrayList<String> getLog(){    
        return this.log;    
    }    
}    
   
class POP3Message{    
   
    protected String from = "";    
    protected String to = "";    
    protected String subject = "";    
    protected String date = "";    
    protected String body = "";    
        
    public void setFrom(String from){    
        this.from = from;    
    }    
        
    public String getFrom(){    
        return this.from;    
    }    
        
    public void setTo(String to){    
        this.to = to;    
    }    
        
    public String getTo(){    
        return this.to;    
    }    
        
    public void setSubject(String subject){    
        this.subject = subject;    
    }    
        
    public String getSubject(){    
        return this.subject;    
    }    
        
    public void setDate(String date){    
        this.date = date;    
    }    
        
    public String getDate(){    
        return this.date;    
    }    
        
    public void setBody(String body){    
        this.body = body;    
    }    
        
    public String getBody(){    
        return this.body;    
    }    
}

http://www.hostprojects.net/snippets/java/145/simple-pop3-class

This code snippet presents a simple POP3 class that can be used to get emails.

Simple POP3 Class

Java