diff --git a/w7/InvalidInputException.java b/w7/InvalidInputException.java
new file mode 100644
index 0000000..4309062
--- /dev/null
+++ b/w7/InvalidInputException.java
@@ -0,0 +1,9 @@
+public class InvalidInputException extends Exception {
+    InvalidInputException() {
+        super("Cannot handle empty input");
+    }
+
+    InvalidInputException(String input, Throwable cause) {
+        super(String.format("Cannot handle input: \"%s\"", input), cause);
+    }
+}
diff --git a/w7/MainSeven.java b/w7/MainSeven.java
new file mode 100644
index 0000000..f8be922
--- /dev/null
+++ b/w7/MainSeven.java
@@ -0,0 +1,43 @@
+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+
+public class MainSeven {
+
+    private static int parseLine(String line) throws InvalidInputException {
+        String trimmed = line.trim();
+        if (trimmed.isEmpty()) {
+            throw new InvalidInputException();
+        }
+
+        try {
+            return Integer.parseInt(trimmed);
+        } catch (NumberFormatException e) {
+            throw new InvalidInputException(trimmed, e);
+        }
+    }
+
+    public static void main(String[] args) {
+        try (FileReader fr = new FileReader("scores.txt")) {
+            BufferedReader br = new BufferedReader(fr);
+
+            int sum = 0;
+            String line;
+            while ((line = br.readLine()) != null) {
+                try {
+                    sum += parseLine(line);
+                } catch (InvalidInputException e) {
+                    System.out.println(e.getMessage());
+                }
+            }
+
+            br.close();
+            System.out.println(sum);
+        } catch (FileNotFoundException e) {
+            System.out.println("File not found: " + e.getMessage());
+        } catch (IOException e) {
+            System.out.println("IOException: " + e.getMessage());
+        }
+    }
+}
diff --git a/w7/MainSevenBefore.java b/w7/MainSevenBefore.java
new file mode 100644
index 0000000..5b72238
--- /dev/null
+++ b/w7/MainSevenBefore.java
@@ -0,0 +1,16 @@
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+
+public class MainSevenBefore {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new FileReader("scores.txt"));
+        int sum = 0;
+        String line;
+        while ((line = br.readLine()) != null) {
+            sum += Integer.parseInt(line);
+        }
+        br.close();
+        System.out.println(sum);
+    }
+}
diff --git a/w7/refactor.diff b/w7/refactor.diff
new file mode 100644
index 0000000..449cc2a
--- /dev/null
+++ b/w7/refactor.diff
@@ -0,0 +1,57 @@
+diff --git "a/.\\MainSevenBefore.java" "b/.\\MainSeven.java"
+index 5b72238..f8be922 100644
+--- "a/.\\MainSevenBefore.java"
++++ "b/.\\MainSeven.java"
+@@ -1,16 +1,43 @@
+ import java.io.BufferedReader;
++import java.io.FileNotFoundException;
+ import java.io.FileReader;
+ import java.io.IOException;
+ 
+-public class MainSevenBefore {
+-    public static void main(String[] args) throws IOException {
+-        BufferedReader br = new BufferedReader(new FileReader("scores.txt"));
+-        int sum = 0;
+-        String line;
+-        while ((line = br.readLine()) != null) {
+-            sum += Integer.parseInt(line);
++public class MainSeven {
++
++    private static int parseLine(String line) throws InvalidInputException {
++        String trimmed = line.trim();
++        if (trimmed.isEmpty()) {
++            throw new InvalidInputException();
++        }
++
++        try {
++            return Integer.parseInt(trimmed);
++        } catch (NumberFormatException e) {
++            throw new InvalidInputException(trimmed, e);
++        }
++    }
++
++    public static void main(String[] args) {
++        try (FileReader fr = new FileReader("scores.txt")) {
++            BufferedReader br = new BufferedReader(fr);
++
++            int sum = 0;
++            String line;
++            while ((line = br.readLine()) != null) {
++                try {
++                    sum += parseLine(line);
++                } catch (InvalidInputException e) {
++                    System.out.println(e.getMessage());
++                }
++            }
++
++            br.close();
++            System.out.println(sum);
++        } catch (FileNotFoundException e) {
++            System.out.println("File not found: " + e.getMessage());
++        } catch (IOException e) {
++            System.out.println("IOException: " + e.getMessage());
+         }
+-        br.close();
+-        System.out.println(sum);
+     }
+ }
diff --git a/w7/scores.txt b/w7/scores.txt
new file mode 100644
index 0000000..079c5d8
--- /dev/null
+++ b/w7/scores.txt
@@ -0,0 +1,7 @@
+96
+85
+74
+62
+
+58
+y76
diff --git a/w7/usage.md b/w7/usage.md
new file mode 100644
index 0000000..b8c3169
--- /dev/null
+++ b/w7/usage.md
@@ -0,0 +1,24 @@
+# 运行记录
+
+## 正常情况
+
+```shell
+$ javac MainSeven.java && java MainSeven
+Cannot handle empty input
+Cannot handle input: "y76"
+375
+```
+
+## 文件移动或删除
+
+```shell
+$ javac MainSeven.java && java MainSeven
+File not found: scores.txt (系统找不到指定的文件。)
+```
+
+## 删除文件读取权限
+
+```shell
+$ javac MainSeven.java && java MainSeven
+File not found: scores.txt (拒绝访问。)
+```