java.util.ConcurrentModificationException --map

key:3-key
key:/v1.02-key
Exception in thread "main" java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1463)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1461)

    public static void main(String[] args) {
        final String StartFlag = "/v1.0";

        Map<String, String> source = new HashMap<>();
        source.put("1-key", "1-value");
        source.put(StartFlag + "2-key", "2-value");
        source.put("3-key", "3-value");

        Iterator<Map.Entry<String, String>> iterator = source.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<String, String> next = iterator.next();
            String key = next.getKey();
            System.out.println("key:" + key);
            String value = next.getValue();
            if (key.startsWith(StartFlag)) {
                key = key.substring(StartFlag.length());
                iterator.remove();
                source.put(key, value);
            }
        }
        System.out.println(source);
    }

        URL resource = getClass().getResource("/swagger/project.json");
        System.out.println("URL:" + resource.toString());
        URI uri = resource.toURI();
        System.out.println("uri:" + uri);

        Path path = Paths.get(uri);
        File file = path.toFile();
        System.out.println("exists:" + file.exists());