Java HashMap转TreeMap

Map<String, String> testMap = new HashMap<String, String>();
("1", "3");
("3", "4");
("2", "1");
("4", "2");
for (String key : ()) {
    (key + "=>" + (key));
}
("========================");
Map<String, String> testMap2 = new TreeMap<String, String>(testMap);
for (String key : ()) {
    (key + "=>" + (key));
}