Lombok @Cleanup的作用是关闭所标注的资源对象，在它的注解注释里已经写得很清楚了

@Cleanup 可以将显示定义的资源，再作用域末尾进行close，前提是定义的类实现了Closeable接口，或自定义了close方法

中文含义与举例

确保您注释的变量声明将通过调用其 close 方法来清除，无论发生什么。 通过将局部变量声明之后的所有语句包装到作用域末尾的 try 块中来实现，该块作为 finally 操作关闭资源。
在@Cleanup 的项目 lombok 功能页面上 可以找到完整的文档。
例子：
   public void copyFile(String in, String out) throws IOException {
       @Cleanup FileInputStream inStream = new FileInputStream(in);
       @Cleanup FileOutputStream outStream = new FileOutputStream(out);
       byte[] b = new byte[65536];
       while (true) {
           int r = inStream.read(b);
           if (r == -1) break;
           outStream.write(b, 0, r);
       }
   }
   
会产生：
   public void copyFile(String in, String out) throws IOException {
       @Cleanup FileInputStream inStream = new FileInputStream(in);
       try {
           @Cleanup FileOutputStream outStream = new FileOutputStream(out);
           try {
               byte[] b = new byte[65536];
               while (true) {
                   int r = inStream.read(b);
                   if (r == -1) break;
                   outStream.write(b, 0, r);
               }
           } finally {
               if (outStream != null) outStream.close();
           }
       } finally {
           if (inStream != null) inStream.close();
       }
   }
   

注解源码

package lombok;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Ensures the variable declaration that you annotate will be cleaned up by calling its close method, regardless
 * of what happens. Implemented by wrapping all statements following the local variable declaration to the
 * end of your scope into a try block that, as a finally action, closes the resource.
 * <p>
 * Complete documentation is found at <a href="https://projectlombok.org/features/Cleanup">the project lombok features page for &#64;Cleanup</a>.
 * <p>
 * Example:
 * <pre>
 * public void copyFile(String in, String out) throws IOException {
 *     &#64;Cleanup FileInputStream inStream = new FileInputStream(in);
 *     &#64;Cleanup FileOutputStream outStream = new FileOutputStream(out);
 *     byte[] b = new byte[65536];
 *     while (true) {
 *         int r = inStream.read(b);
 *         if (r == -1) break;
 *         outStream.write(b, 0, r);
 *     }
 * }
 * </pre>
 * 
 * Will generate:
 * <pre>
 * public void copyFile(String in, String out) throws IOException {
 *     &#64;Cleanup FileInputStream inStream = new FileInputStream(in);
 *     try {
 *         &#64;Cleanup FileOutputStream outStream = new FileOutputStream(out);
 *         try {
 *             byte[] b = new byte[65536];
 *             while (true) {
 *                 int r = inStream.read(b);
 *                 if (r == -1) break;
 *                 outStream.write(b, 0, r);
 *             }
 *         } finally {
 *             if (outStream != null) outStream.close();
 *         }
 *     } finally {
 *         if (inStream != null) inStream.close();
 *     }
 * }
 * </pre>
 */
@Target(ElementType.LOCAL_VARIABLE)
@Retention(RetentionPolicy.SOURCE)
public @interface Cleanup {
	/** @return The name of the method that cleans up the resource. By default, 'close'. The method must not have any parameters. */
	String value() default "close";
}

java代码加了@Cleanup后，可以查看编译成的class文件长成啥样了