[Add] Framework-API 补充提交一个工具类;

[Add] CollectionUtils 添加集合工具类;

ContentGrabbingJi-framework-api/src/main/java/net/lamgc/cgj/bot/framework/util/CollectionUtils.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2020  LamGC
+ *
+ * ContentGrabbingJi is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * ContentGrabbingJi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.lamgc.cgj.bot.framework.util;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Function;
+
+/**
+ * 额外的集合工具类.
+ * @author LamGC
+ */
+public class CollectionUtils {
+
+    /**
+     * 通过 keySet 和取值接口构造对应 Map.
+     * 处理时会自动跳过 key 为 null 的情况.
+     * @param keySet 存储了所有 key 的 Set 对象.
+     * @param valueSource 可根据 key 获取 value 的接口.
+     * @param <K> 键类型.
+     * @param <V> 值类型.
+     * @return 返回对应 Map.
+     */
+    public static <K, V> Map<K, V> toMap(Set<K> keySet, Function<K, V> valueSource) {
+        Map<K, V> map = new HashMap<>(keySet.size());
+        keySet.forEach(key -> {
+            if(key != null) {
+                map.put(key, valueSource.apply(key));
+            }
+        });
+        return map;
+    }
+
+
+}