remove package to be java_collections

Author: fishercoder1534

src/main/java/hashmap/MainApp.java …/main/java/java_collections/MainApp.javasrc/main/java/hashmap/MainApp.java renamed to src/main/java/java_collections/MainApp.java src/main/java/hashmap/MainApp.java renamed to src/main/java/java_collections/MainApp.java

@@ -1,4 +1,4 @@
-package hashmap;
+package java_collections;
 
 import java.util.HashMap;
 import java.util.Map;