1、考虑用静态工厂方法代替构造器
public class Beyond { public static <K, V> HashMap<K, V> newInstance() { return new HashMap<K, V>(); } public static void main(String[] args) { HashMap<String, String> hashMap = Beyond.newInstance(); for (int i = 0; i < 9; i++) { hashMap.put("" + i, "" + i + i); } System.out.println(hashMap); System.out.println("----------------"); HashMap<String,String> hashMap1 = new HashMap<String, String>(10); for (int i = 0; i < 9; i++) { hashMap1.put("" + i, "" + i + i); } System.out.println(hashMap); } }