java8 - 多线程时间安全问题

import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class TestSimpleDateFormat {

    public static void main(String[] args) throws Exception {

        /*SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");

        Callable<Date> task = new Callable<Date>() {

            @Override
            public Date call() throws Exception {
                return sdf.parse("20161121");
            }

        };

        ExecutorService pool = Executors.newFixedThreadPool(10);

        List<Future<Date>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {
            results.add(pool.submit(task));
        }

        for (Future<Date> future : results) {
            System.out.println(future.get());
        }

        pool.shutdown();*/

        //解决多线程安全问题
        /*Callable<Date> task = new Callable<Date>() {

            @Override
            public Date call() throws Exception {
                return DateFormatThreadLocal.convert("20161121");
            }

        };

        ExecutorService pool = Executors.newFixedThreadPool(10);

        List<Future<Date>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {
            results.add(pool.submit(task));
        }

        for (Future<Date> future : results) {
            System.out.println(future.get());
        }

        pool.shutdown();*/

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");

        Callable<LocalDate> task = new Callable<LocalDate>() {

            @Override
            public LocalDate call() throws Exception {
                LocalDate ld = LocalDate.parse("20161121", dtf);
                return ld;
            }

        };

        ExecutorService pool = Executors.newFixedThreadPool(10);

        List<Future<LocalDate>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {
            results.add(pool.submit(task));
        }

        for (Future<LocalDate> future : results) {
            System.out.println(future.get());
        }

        pool.shutdown();
    }

}

DateFormatThreadLocal

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatThreadLocal {

    private static final ThreadLocal<DateFormat> df = new ThreadLocal<DateFormat>(){

        protected DateFormat initialValue(){
            return new SimpleDateFormat("yyyyMMdd");
        }

    };

    public static final Date convert(String source) throws ParseException{
        return df.get().parse(source);
    }

}