Getting huge echo with java recording

Question

I am getting huge echo while recording with java sound api. But I expect a recording without any echo. How can I do that ? Or what could be the problem with my below two classes ??

Recorder.java

package media;

import javax.sound.sampled.*;

public class Recorder extends Thread{
    public static final int DEFAULT_AUDIO_RECORD_FRAME_DURATION = 60; /// 60ms
    private TargetDataLine line;
    private boolean running;

    public Recorder(){
        super();
    }
    @Override
    public void run(){
        running = true;
        try {
            

            AudioFormat format = new AudioFormat(16000, 16, 1, true, false);
            DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);

            // checks if system supports the data line
            if (!AudioSystem.isLineSupported(info)) {
                System.exit(0);
            }

            line = (TargetDataLine) AudioSystem.getLine(info);
            line.open(format);
            line.start();   // start capturing

            AudioInputStream ais = new AudioInputStream(line);
            byte [] data = new byte[1960]; /////frame size 1960. 60 ms data
            int readLen;
            int sequenceNumber = 0;
            try {
                while (running) {
                    readLen = ais.read(data);
                    if(readLen <= 0) {
                        break;
                    }
                    processEncodingAndSendToServer(data);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try{
                line.stop();
            }catch (Exception e){}
            try{
                line.close();
            }catch (Exception e){}
        }
    }
    public void shutDown(){
        running = false;
    }
}

Player.java

package media;


import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.SourceDataLine;

public class Player extends Thread{
    private boolean running;

    public Player(){
        super();
    }

    @Override
    public void run(){

        int readLen;
        running = true;
        SourceDataLine sline = null;
        int sequenceNumber = 0;
        try{

            AudioFormat format = new AudioFormat(16000, 16, 1, true, false);
            byte [] data = new byte[1960];
            DataLine.Info info = new DataLine.Info(SourceDataLine.class, format);

            sline = (SourceDataLine) AudioSystem.getLine(info);

            sline.open(format);
            sline.start();   // start capturing

            while(running){
                readLen = getPacketForPlay(data, 0);  ////get a packet of length 1960 after deocoding which is received from server
                if(readLen <= 0) {
                    continue;
                }
                sline.write(data, 0 , readLen);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                sline.stop();
                sline.close();
            }catch (Exception e){}
        }
    }

    public void shutDown(){
        running = false;
        this.interrupt();
    }
}

The above two classes are simple thread running independently while this conference app is running. I am getting huge echo even in two persons conversation. And this problem is more severe with more people on the call. And the strange thing is that getting this problem even with headphone connected pc. I am sure I am making some mistake with my code here. Need some help desperately.