diff --git a/Contact.java b/Contact.java
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+++ b/Contact.java
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+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.micode.notes.data;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.provider.ContactsContract.CommonDataKinds.Phone;
+import android.provider.ContactsContract.Data;
+import android.telephony.PhoneNumberUtils;
+import android.util.Log;
+
+import java.util.HashMap;
+
+public class Contact {
+    // 用于缓存联系人信息，避免多次查询同一个号码
+    private static HashMap<String, String> sContactCache;
+    private static final String TAG = "Contact";  // 用于Log输出的TAG
+
+    // 用于查询联系人名称的SQL条件，依赖于手机号的最小匹配格式
+    private static final String CALLER_ID_SELECTION = "PHONE_NUMBERS_EQUAL(" + Phone.NUMBER
+    + ",?) AND " + Data.MIMETYPE + "='" + Phone.CONTENT_ITEM_TYPE + "'"
+    + " AND " + Data.RAW_CONTACT_ID + " IN "
+            + "(SELECT raw_contact_id "
+            + " FROM phone_lookup"
+            + " WHERE min_match = '+')";
+
+    // 获取某个电话号对应的联系人名称
+    public static String getContact(Context context, String phoneNumber) {
+        // 如果缓存为空，初始化缓存
+        if(sContactCache == null) {
+            sContactCache = new HashMap<String, String>();
+        }
+
+        // 如果缓存中已有该电话号码的联系人信息，直接返回
+        if(sContactCache.containsKey(phoneNumber)) {
+            return sContactCache.get(phoneNumber);
+        }
+
+        // 通过PhoneNumberUtils将电话号码转为符合最小匹配格式的号码
+        String selection = CALLER_ID_SELECTION.replace("+",
+                PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));
+        
+        // 查询联系人数据库，根据号码查找联系人名称
+        Cursor cursor = context.getContentResolver().query(
+                Data.CONTENT_URI,   // 数据源：联系人数据
+                new String[] { Phone.DISPLAY_NAME },  // 查询字段：联系人名称
+                selection,  // 查询条件：号码与条件匹配
+                new String[] { phoneNumber },  // 查询参数：电话号码
+                null);  // 排序
+
+        // 如果查询成功，处理返回结果
+        if (cursor != null && cursor.moveToFirst()) {
+            try {
+                // 获取查询到的联系人名称
+                String name = cursor.getString(0);
+                // 将查询到的联系人名称缓存起来
+                sContactCache.put(phoneNumber, name);
+                return name;
+            } catch (IndexOutOfBoundsException e) {
+                // 如果查询结果异常，记录日志
+                Log.e(TAG, " Cursor get string error " + e.toString());
+                return null;
+            } finally {
+                // 最后关闭游标，释放资源
+                cursor.close();
+            }
+        } else {
+            // 如果没有找到匹配的联系人，记录日志并返回null
+            Log.d(TAG, "No contact matched with number:" + phoneNumber);
+            return null;
+        }
+    }
+}
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