之前已经写过一篇通用Builder来构建实例对象的（基于Java8的新特性写一个通用的Builder工具类_java手动写一个builder-CSDN博客）但是这个builder不能构建集合，也就是list和map，今天突然心血来潮，想写写集合类的builder，这两个builder相比于通用的builder要简单易懂的多，废话不多说，直接上代码：

Mapbuilder：

public class MapBuilder<K, V> {private Map<K, V> map;private MapBuilder(Map<K, V> map) {this.map = map;}public static <K, V> MapBuilder<K, V> ofMap() {return new MapBuilder<>(new HashMap<K, V>());}public MapBuilder<K, V> put(K key, V value) {this.map.put(key, value);return this;}public Map<K, V> build() {return this.map;}public static void main(String[] args) {Map<String, Integer> map = MapBuilder.<String, Integer>ofMap().put("a", 1).put("b", 2).put("c", 3).build();System.out.println(map); // 输出：{a=1, b=2, c=3}}
}

ListBuilder:

public class ListBuilder<T> {private List<T> list;private ListBuilder(List<T> list) {this.list = list;}public static <T> ListBuilder<T> ofList() {return new ListBuilder(new ArrayList<T>());}public ListBuilder<T> add(T t) {this.list.add(t);return this;}public List<T> build() {return this.list;}public static void main(String[] args) {List<Integer> integers = ListBuilder.<Integer>ofList().add(1).build();System.err.println(integers);}
}