recipe_i_9_i, recipe_i_9_ii 에러

[seosej]

Cashier.java 의 openFile()에 @PostConstruct 애너테이션, closeFile()에 @PreDestory 애너테이션 붙여줘야 에러가 나지 않습니다.

에러 내용

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.io.BufferedWriter.write(String)" because "this.writer" is null
        at com.apress.spring6recipes.shop.Cashier.checkout(Cashier.java:34)
        at com.apress.spring6recipes.shop.Main.main(Main.java:27)

Cashier.java

package com.apress.spring6recipes.shop;

import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.OpenOption;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.time.LocalDateTime;

import jakarta.annotation.PostConstruct;
import jakarta.annotation.PreDestroy;

public class Cashier {

    private final String fileName;
    private final String path;

    private BufferedWriter writer;

    public Cashier(String fileName, String path) {
        this.fileName = fileName;
        this.path = path;
    }

    @PostConstruct
    public void openFile() throws IOException {
        var options = new OpenOption[] {
                        StandardOpenOption.CREATE,
                        StandardOpenOption.APPEND };
        var file = Path.of(path, fileName + ".txt");
        Files.createDirectories(file.getParent());
        writer = Files.newBufferedWriter(file, StandardCharsets.UTF_8, options);
    }

    public void checkout(ShoppingCart cart) throws IOException {
        writer.write(LocalDateTime.now() + "\t" + cart.getItems() + "\r\n");
        writer.flush();
    }

    @PreDestroy
    public void closeFile() throws IOException {
        writer.close();
    }
}