1、Java8之前日期的痛点

1、构造年的日期需传入year-1900

2、每周的日期从周一开始，不符合各国用户习惯

3、 TimeZone提供时区支持但不好用，且线程不安全

4、日期格式化规划混乱，不应该在java.text包中

2、Java8中的改变

1、日期规划到了同一个包中:java.time.*

2、日期表示很灵活，可读性高

3、解决了线程安全问题

3、线程安全问题体现在哪里？

参见TestSimpleDateFormat

传统方式如何解决？

通过ThreadLocal

4、源码

TestSimpleDateFormat

package com.atguigu.java8;

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 task = new Callable() {

@Override

public Date call() throws Exception {

return sdf.parse("20161121");

}

};

ExecutorService pool = Executors.newFixedThreadPool(10);

List> results = new ArrayList<>();

for (int i = 0; i < 10; i++) {

results.add(pool.submit(task));

}

for (Future future : results) {

System.out.println(future.get());

}

pool.shutdown();*/

//解决多线程安全问题

/*Callable task = new Callable() {

@Override

public Date call() throws Exception {

return DateFormatThreadLocal.convert("20161121");

}

};

ExecutorService pool = Executors.newFixedThreadPool(10);

List> results = new ArrayList<>();

for (int i = 0; i < 10; i++) {

results.add(pool.submit(task));

}

for (Future future : results) {

System.out.println(future.get());

}

pool.shutdown();*/

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

Callable task = new Callable() {

@Override

public LocalDate call() throws Exception {

LocalDate ld = LocalDate.parse("20161121", dtf);

return ld;

}

};

ExecutorService pool = Executors.newFixedThreadPool(10);

List> results = new ArrayList<>();

for (int i = 0; i < 10; i++) {

results.add(pool.submit(task));

}

for (Future future : results) {

System.out.println(future.get());

}

pool.shutdown();

}

}

DateFormatThreadLocal

package com.atguigu.java8;

import java.text.DateFormat;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class DateFormatThreadLocal {

private static final ThreadLocal df = new ThreadLocal(){

protected DateFormat initialValue(){

return new SimpleDateFormat("yyyyMMdd");

}

};

public static final Date convert(String source) throws ParseException{

return df.get().parse(source);

}

}