diff --git a/src/main/java/com/github/hcsp/collection/Main.java b/src/main/java/com/github/hcsp/collection/Main.java
index ae0f842..900e80c 100644
--- a/src/main/java/com/github/hcsp/collection/Main.java
+++ b/src/main/java/com/github/hcsp/collection/Main.java
@@ -1,12 +1,20 @@
 package com.github.hcsp.collection;
 
-import java.util.Arrays;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.Arrays;
+import java.util.Objects;
 
 public class Main {
     // 请编写一个方法，获得a和b集合中的公共元素。
-    public static Set<Person> commonElementsIn(List<Person> a, List<Person> b) {}
+    public static Set<Person> commonElementsIn(List<Person> a, List<Person> b) {
+        Set<Person> set = new HashSet<>();
+        set.addAll(a);
+        set.retainAll(b);
+        return set;
+
+    }
 
     // Person类，如果两个Person对象的name相等，则认为这两个对象相等。
     public static class Person {
@@ -23,6 +31,23 @@ public String getName() {
         public void setName(String name) {
             this.name = name;
         }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) {
+                return true;
+            }
+            if (o == null || getClass() != o.getClass()) {
+                return false;
+            }
+            Person person = (Person) o;
+            return Objects.equals(name, person.name);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(name);
+        }
     }
 
     public static void main(String[] args) {
@@ -31,3 +56,4 @@ public static void main(String[] args) {
         System.out.println(commonElementsIn(list1, list2));
     }
 }
+