我有一个日期对象,需要格式化它以进行缓存查找,simpledateformat不是线程安全的吗？

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.concurrent.ConcurrentHashMap;

public class CacheManager {
    private static final ConcurrentHashMap<String, LocalDate> DATE_MAP = new ConcurrentHashMap<>();
    private static final DateTimeFormatter DATE_FORMAT = DateTimeFormatter.ofPattern("yyyy-MM-dd");

    public static void put(String key, LocalDate date) {
        DATE_MAP.put(key, date);
    }

    public static LocalDate get(String key) {
        return DATE_MAP.get(key);
    }
}

import java.text.SimpleDateFormat;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public class CacheManager {
    private static final Map<String, String> DATE_MAP = Collections.synchronizedMap(new HashMap<>());
    private static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd");

    public static void put(String key, String date) {
        DATE_MAP.put(key, date);
    }

    public static String get(String key) {
        return DATE_MAP.get(key);
    }
}