update:demo5

com/study/demo5/FileStat.java

@@ -0,0 +1,25 @@
+package com.study.demo5;
+
+import java.io.*;
+
+public class FileStat {
+  public long countBytes(String filePath) {
+    long totalBytes = 0;
+
+    try (FileInputStream fis = new FileInputStream(filePath)) {
+
+      byte[] buffer = new byte[1024];
+      int bytesRead;
+
+      while ((bytesRead = fis.read(buffer)) != -1) {
+        totalBytes += bytesRead;
+      }
+
+    } catch (IOException e) {
+      System.err.println("文件读取失败: " + e.getMessage());
+      return -1;
+    }
+
+    return totalBytes;
+  }
+}