本文目录导读：
我来为你展示Java中try-with-resources的多个实用案例，从基础到高级。
基础用法：文件操作
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class BasicExample {
public static void main(String[] args) {
// 自动关闭文件资源
try (BufferedReader reader = new BufferedReader(new FileReader("test.txt"))) {
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
多资源管理
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
public class MultiResourceExample {
public static void copyFile(String source, String target) {
// 同时管理多个资源，按声明顺序逆序关闭
try (InputStream in = Files.newInputStream(Paths.get(source));
OutputStream out = Files.newOutputStream(Paths.get(target))) {
byte[] buffer = new byte[1024];
int length;
while ((length = in.read(buffer)) > 0) {
out.write(buffer, 0, length);
}
System.out.println("文件复制成功！");
} catch (IOException e) {
System.err.println("复制失败: " + e.getMessage());
}
}
}
自定义资源类
public class CustomResourceExample {
// 自定义资源类，实现 AutoCloseable 接口
static class DatabaseConnection implements AutoCloseable {
private String name;
public DatabaseConnection(String name) {
this.name = name;
System.out.println("打开数据库连接: " + name);
}
public void query(String sql) {
System.out.println("执行查询: " + sql);
if (sql.contains("error")) {
throw new RuntimeException("查询失败！");
}
}
@Override
public void close() {
System.out.println("关闭数据库连接: " + name);
}
}
public static void main(String[] args) {
// 无论是否发生异常，都会自动关闭资源
try (DatabaseConnection conn = new DatabaseConnection("Oracle")) {
conn.query("SELECT * FROM users");
conn.query("error - 触发异常");
} catch (RuntimeException e) {
System.out.println("捕获异常: " + e.getMessage());
}
}
}
资源与异常处理
import java.io.*;
public class ExceptionHandlingExample {
// 演示 suppress exception（被抑制的异常）
public static void showSuppressedExceptions() {
try (BufferedReader reader = new BufferedReader(
new FileReader("nonexistent.txt"))) {
String line = reader.readLine();
} catch (IOException e) {
System.out.println("主异常: " + e.getMessage());
Throwable[] suppressed = e.getSuppressed();
if (suppressed.length > 0) {
System.out.println("被抑制的异常数量: " + suppressed.length);
for (Throwable t : suppressed) {
System.out.println(" 抑制异常: " + t.getMessage());
}
}
}
}
// 传统方式的对比
public static void traditionalWay() throws IOException {
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader("test.txt"));
String line = reader.readLine();
} finally {
if (reader != null) {
reader.close(); // 必须手动关闭，且可能掩盖主异常
}
}
}
// 新方式的对比 - 更简洁
public static void modernWay() throws IOException {
try (BufferedReader reader = new BufferedReader(new FileReader("test.txt"))) {
String line = reader.readLine();
} // 自动关闭
}
}
网络资源管理
import java.io.*;
import java.net.Socket;
import java.net.URL;
public class NetworkResourceExample {
// 管理网络连接
public static void downloadContent(String urlString) {
try (Socket socket = new Socket("example.com", 80);
OutputStream os = socket.getOutputStream();
InputStream is = socket.getInputStream()) {
// 发送HTTP请求
String request = "GET " + urlString + " HTTP/1.1\r\n" +
"Host: example.com\r\n" +
"Connection: close\r\n\r\n";
os.write(request.getBytes());
os.flush();
// 读取响应
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = is.read(buffer)) != -1) {
System.out.print(new String(buffer, 0, bytesRead));
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
互斥锁资源
import java.util.concurrent.locks.ReentrantLock;
public class LockResourceExample {
private static ReentrantLock lock = new ReentrantLock();
// 自定义AutoCloseable的锁
static class LockHelper implements AutoCloseable {
public LockHelper() {
lock.lock();
System.out.println("获取锁");
}
@Override
public void close() {
lock.unlock();
System.out.println("释放锁");
}
}
public static void main(String[] args) {
// 使用try-with-resources自动管理锁
try (LockHelper helper = new LockHelper()) {
System.out.println("执行临界区代码");
// 业务逻辑...
}
}
}
结合Lambda表达式
import java.io.*;
import java.nio.file.*;
public class FunctionalExample {
public static void processFile(String filePath) {
// 更简洁的写法，支持链式操作
try (Stream<String> lines = Files.lines(Paths.get(filePath))) {
lines.filter(line -> !line.startsWith("#")) // 过滤注释
.map(String::trim) // 去除空格
.filter(line -> !line.isEmpty()) // 过滤空行
.forEach(System.out::println); // 打印
} catch (IOException e) {
System.err.println("读取文件失败: " + e.getMessage());
}
}
}
数据库连接管理（模拟）
import java.sql.*;
public class DatabaseExample {
public static void queryUsers() {
String url = "jdbc:mysql://localhost:3306/mydb";
String user = "root";
String password = "password";
// JDBC 7+ 支持try-with-resources
try (Connection conn = DriverManager.getConnection(url, user, password);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM users")) {
while (rs.next()) {
System.out.println("用户: " + rs.getString("name"));
}
} catch (SQLException e) {
System.err.println("数据库操作失败: " + e.getMessage());
}
}
}
实际项目中的完整示例
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
public class RealWorldExample {
public static class User {
private String name;
private String email;
public User(String name, String email) {
this.name = name;
this.email = email;
}
@Override
public String toString() {
return "User{name='" + name + "', email='" + email + "'}";
}
}
// 从CSV文件读取用户数据
public static List<User> readUsersFromCsv(String filePath) {
List<User> users = new ArrayList<>();
try (BufferedReader reader = new BufferedReader(
new InputStreamReader(
new FileInputStream(filePath),
StandardCharsets.UTF_8))) {
String line;
boolean firstLine = true;
while ((line = reader.readLine()) != null) {
if (firstLine) { // 跳过表头
firstLine = false;
continue;
}
String[] parts = line.split(",");
if (parts.length >= 2) {
users.add(new User(parts[0].trim(), parts[1].trim()));
}
}
} catch (FileNotFoundException e) {
System.err.println("文件不存在: " + e.getMessage());
} catch (IOException e) {
System.err.println("读取文件错误: " + e.getMessage());
}
return users;
}
// 将用户数据写入JSON文件（简化版）
public static void writeUsersToJson(List<User> users, String filePath) {
try (BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(
new FileOutputStream(filePath),
StandardCharsets.UTF_8))) {
writer.write("[");
for (int i = 0; i < users.size(); i++) {
User user = users.get(i);
if (i > 0) writer.write(",");
writer.write(String.format(
"\n {\"name\": \"%s\", \"email\": \"%s\"}",
user.name, user.email
));
}
writer.write("\n]");
System.out.println("成功写入 " + users.size() + " 个用户到 " + filePath);
} catch (IOException e) {
System.err.println("写入文件错误: " + e.getMessage());
}
}
public static void main(String[] args) {
// 完整流程示例
List<User> users = readUsersFromCsv("users.csv");
users.forEach(System.out::println);
writeUsersToJson(users, "users.json");
}
}
高级技巧：封装资源管理
import java.io.*;
import java.util.function.Consumer;
public class ResourceWrapperExample {
// 通用的资源处理器
public static <T extends AutoCloseable> void withResource(
ResourceFactory<T> factory,
Consumer<T> consumer,
String resourceName) {
try (T resource = factory.create()) {
consumer.accept(resource);
} catch (Exception e) {
System.err.printf("处理资源 '%s' 失败: %s%n",
resourceName, e.getMessage());
}
}
@FunctionalInterface
interface ResourceFactory<T> {
T create() throws Exception;
}
static class TempFile implements AutoCloseable {
public TempFile(String name) {
System.out.println("创建临时文件: " + name);
}
public void write(String content) {
System.out.println("写入内容: " + content);
}
@Override
public void close() {
System.out.println("删除临时文件");
}
}
public static void main(String[] args) {
// 使用通用处理器
withResource(
() -> new TempFile("temp.txt"),
file -> file.write("测试内容"),
"临时文件"
);
}
}
- 自动关闭：不用手动调用
close()方法 - 多资源管理：可同时管理多个资源
- 异常处理：主异常不会被覆盖，额外异常作为抑制异常加入
- 简洁代码：减少finally块的使用
- 自定义资源：实现
AutoCloseable接口即可 - 顺序保证：资源按声明顺序的逆序关闭
使用try-with-resources能让代码更安全、更简洁，是现代Java开发中的推荐实践！
