Java8新特性一点通 | 回顾字符转日期&JoinArray使用

2024-09-05 13:35:26

- StringToDate日期转换
- Join Array使用

StringToDate日期转换

Convert string to date in ISO8601 format
- 利用LocalDate.parse(CharSequence text) 直接以ISO8601方式格式化

 String originalDate = "2018-08-07";

        LocalDate localDate = LocalDate.parse(originalDate);

        System.out.println("Date:"+localDate);

Output:

Date:2018-08-07

Convert string to date in custom formats
- 利用DateTimeFormatter.ofPattern(String pattern)和LocalDate.parse(CharSequence text, DateTimeFormatter formatter)结合对日期以指定格式格式化

String originalDate1 = "2018-08-07 10:47:00";

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm:ss");

        LocalDate localDate1 = LocalDate.parse(originalDate1,formatter);

        System.out.println("custom date:"+localDate1);

Output:

custom date:2018-08-07

Join Array使用

对现有数组添加字符串组成新的字符串的几个方法：

- String.join(CharSequence delimiter, CharSequence… elements) 场景：可以对现有数组添加分隔符组成新的字符串

String joinedString = String.join(",", "hello", "world", "!");

        System.out.println("示例1:" + joinedString);

Output:

示例1:hello,world,!

String.join(CharSequence delimiter, Iterable elements) 场景：可以对现有列表添加分隔符组成新的字符串

List<String> strList = Arrays.asList("hello", "world", "!");

        String joinedString1 = String.join(",", strList);

        System.out.println("示例2:" + joinedString1);

Output:

示例2:hello,world,!

StringJoiner(CharSequence delimiter) 场景：添加分隔符

 StringJoiner stringJoiner1 = new StringJoiner(",");

        stringJoiner1.add("hello").add("world").add("!");

        System.out.println("示例3:" + stringJoiner1.toString());

Output:

示例3:hello,world,!

StringJoiner(CharSequence delimiter, CharSequence prefix, CharSequence suffix) 场景:添加分隔符以及前后缀

StringJoiner stringJoiner2 = new StringJoiner(",", "[", "]");

        stringJoiner2.add("hello").add("world").add("!");

        System.out.println("示例4:" + stringJoiner2.toString());

Output:

示例4:[hello,world,!]

Collectors.joining 场景:在lambda表达式里面用，针对添加分隔符和前后缀的场景

  List<String> strList1 = Arrays.asList("hello", "world", "!");

        String joinedString3 = strList1.stream().collect(Collectors.joining(",","[","]"));

        System.out.println("示例5:"+joinedString3);

Output:

示例5:[hello,world,!]

StringUtils.join() 场景：跟以上用法差不多，使用工具类去把数据和列表组成单独的字符串

String[] strArray = {"hello", "world", "!"};

        String joinedString4 = StringUtils.join(strArray, ",");

        System.out.println("示例6:" + joinedString4);

Output:

示例6:hello,world,!

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