JavaSE 之传统日期格式化的线程问题

Ella ·

更新时间:2024-11-01

· 897 次阅读

需求：让多线程同时去解析日期 错误示范

public class Test1 {
	@Test
	public void test01() throws Exception {
		//格式化日期类
		SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
		//任务类：用于解析成Date对象
		Callable task = new Callable() {
			@Override
			public Date call() throws Exception {
				return sdf.parse("20200123");
			}
		};
		//Date解析结果的集合
		List<Future> list = new ArrayList();
		//线程池
		ExecutorService pool = Executors.newFixedThreadPool(10);
		for (int i = 1; i <= 10; i++) {
			Future future = pool.submit(task);
			list.add(future);
		}
		//打印结果
		for (Future future : list) {
			System.out.println(future.get());
		}
		//关闭线程池
		pool.shutdown();
	}
}

正确示范

public class Test1 {
	@Test
	public void test01() throws Exception {
		//任务类：用于解析成Date对象
		Callable task = new Callable() {
			@Override
			public Date call() throws Exception {
				return SimpleDateFormatThreadLocal.convert("20200123");
			}
		};
		//Date解析结果的集合
		List<Future> list = new ArrayList();
		//线程池
		ExecutorService pool = Executors.newFixedThreadPool(10);
		for (int i = 1; i <= 10; i++) {
			Future future = pool.submit(task);
			list.add(future);
		}
		//打印结果
		for (Future future : list) {
			System.out.println(future.get());
		}
		//关闭线程池
		pool.shutdown();
	}
}
class SimpleDateFormatThreadLocal{
	private static final ThreadLocal local = new ThreadLocal(){
		//重写父类的方法：返回此线程局部变量的当前线程的“初始值”。 
		protected SimpleDateFormat initialValue() {
			return new SimpleDateFormat("yyyyMMdd");
		}
	};
	public static Date convert(String str) throws ParseException{
		SimpleDateFormat sdf = local.get();
		Date date = sdf.parse(str);
		return date;
	}
}

JDK1.8后正确示范

public class Test1 {
	@Test
	public void test01() throws Exception {
		//格式化日期类
		DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");
		//任务类：用于解析成Date对象
		Callable task = new Callable() {
			@Override
			public LocalDate call() throws Exception {
				return LocalDate.parse("20200123",dtf);
			}
		};
		//Date解析结果的集合
		List<Future> list = new ArrayList();
		//线程池
		ExecutorService pool = Executors.newFixedThreadPool(10);
		for (int i = 1; i <= 10; i++) {
			Future future = pool.submit(task);
			list.add(future);
		}
		//打印结果
		for (Future future : list) {
			System.out.println(future.get());
		}
		//关闭线程池
		pool.shutdown();
	}
}

作者：晞晞奶爸

格式化线程 javase

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