import java.util.*;

public class ResourceWriter {

    public Map<Integer, Exception> exceptions = new HashMap<Integer, Exception>();
    private Map<String, String> map = new HashMap<String, String>();
    volatile boolean copying=false;
    volatile int count=0;

    public void write(String s){
        if (map.size()<100){
            while (copying){
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            map.put(UUID.randomUUID().toString(), s);
            return;
        }
        sendSomewhere();
    }

    private synchronized void sendSomewhere() {
        copying=true;
        if (map.size()<100){
            copying=false;
            return;
        }


        System.out.println("Before flush:"+map.size()+";"+ (++count));
        Map<String, String> map2 = null;
        try {
            map2 = new HashMap<String, String>(map);
        } catch (Exception e) {
            exceptions.put(count, e);
            return;
        }
        map.clear();
        System.out.println("After flush:"+map.size()+";"+count);
        copying=false;
//        отправляем этот map2 куда-нибудь, эмуляция задержки
        try {
            Thread.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

}

public class Worker extends Thread{

    private ResourceWriter rw;

    public Worker(ResourceWriter rw) {
        super();
        this.rw = rw;
    }

    @Override
    public void run() {
        for (int i=0;i<100;i++){
            rw.write(UUID.randomUUID().toString());
        }
    }
}

public class Main {

    public static void main(String[] args) {
        ResourceWriter rw = new ResourceWriter();
        for (int i=0;i<100;i++){
            new Worker(rw).start();
        }
        try {
            Thread.sleep(20000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        for (Integer key:rw.exceptions.keySet()){
            System.out.println(key+";"+rw.exceptions.get(key).toString());
        }
    }

}

private synchronized void sendSomewhere() 

    volatile boolean copying=false;
    

    public void write(String s){
        if (map.size()<100){
            while (copying){
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            map.put(UUID.randomUUID().toString(), s);
            return;
        }