update:demo5

com/study/demo5/DataIO.java

@@ -0,0 +1,40 @@
+package com.study.demo5;
+
+import java.io.*;
+
+public class DataIO {
+  public void writeConfig(String path) {
+    try (DataOutputStream dos = new DataOutputStream(
+        new FileOutputStream(path))) {
+
+      dos.writeUTF("李华"); // 用户名
+      dos.writeInt(25); // 年龄
+      dos.writeBoolean(true); // 是否启用
+      dos.writeDouble(1234.56); // 余额
+
+      System.out.println("配置写入成功: " + path);
+
+    } catch (IOException e) {
+      System.err.println("写入配置失败: " + e.getMessage());
+    }
+  }
+
+  public void readConfig(String path) {
+    try (DataInputStream dis = new DataInputStream(
+        new FileInputStream(path))) {
+
+      String username = dis.readUTF();
+      int age = dis.readInt();
+      boolean enabled = dis.readBoolean();
+      double balance = dis.readDouble();
+
+      System.out.println("用户名: " + username);
+      System.out.println("年龄: " + age);
+      System.out.println("是否启用: " + enabled);
+      System.out.println("余额: " + balance);
+
+    } catch (IOException e) {
+      System.err.println("读取配置失败: " + e.getMessage());
+    }
+  }
+}

com/study/demo5/FileCopy.java

@@ -0,0 +1,20 @@
+package com.study.demo5;
+
+import java.io.*;
+
+public class FileCopy {
+  public void copy(String source, String target) {
+    try (FileInputStream fis = new FileInputStream(source);
+        FileOutputStream fos = new FileOutputStream(target)) {
+      byte[] buffer = new byte[1024];
+      int bytesRead;
+      while ((bytesRead = fis.read(buffer)) != -1) {
+        fos.write(buffer, 0, bytesRead);
+      }
+    } catch (FileNotFoundException e) {
+      System.err.println("源文件未找到: " + e.getMessage());
+    } catch (IOException e) {
+      System.err.println("文件复制失败: " + e.getMessage());
+    }
+  }
+}

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;
+  }
+}

com/study/demo5/Main.java

@@ -0,0 +1,17 @@
+package com.study.demo5;
+
+ public class Main {
+    public static void main(String[] args) {
+        // 7.1 测试
+        FileCopy fc = new FileCopy();
+        fc.copy("source.txt", "target.txt");
+        // 7.2 测试
+        DataIO dataIO = new DataIO();
+        dataIO.writeConfig("config.bin");
+        dataIO.readConfig("config.bin");
+        // 7.3 测试
+        FileStat fs = new FileStat();
+        long size = fs.countBytes("test3.txt");
+        System.out.println("文件大小: " + size + " 字节");
+    }
+}

flake.nix

@@ -3,7 +3,7 @@
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
   outputs = { self, nixpkgs }:
   let
-    supportedSystems = [ "x86_64-linux" "aarch64-linux" ];
+    supportedSystems = [ "x86_64-linux" ];
     forEachSupportedSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
       pkgs = import nixpkgs { inherit self system; };
     });