Apache-Commons-*
字符串
判断字符串是否为空白字符串
以前判断字符串是否为空:
if ((name == null) || (name.isEmpty())){}
使用 apache-common-lang3
的 StringUtils
:
void testIsBlank() {
// true
Assertions.assertTrue(StringUtils.isBlank(" "));
// true
Assertions.assertTrue(StringUtils.isBlank(""));
// true
Assertions.assertTrue(StringUtils.isBlank(null));
// false
Assertions.assertFalse(StringUtils.isBlank("foo"));
// true
Assertions.assertTrue(StringUtils.isAnyBlank(null, " "));
// false
Assertions.assertFalse(StringUtils.isAnyBlank("foo", " bar "));
}
左边填充字符串
有时候我们需要生成流水号,例如4位数的流水号,从1
开始其余用字符'0'
填充,就可以使用 leftPad
方法,示例如下:
@Test
void testLeftPad() {
// 0001
Assertions.assertEquals("0001", StringUtils.leftPad("1", 4, '0'));
}
右边填充字符串
@Test
void testRightPad() {
// 1000
Assertions.assertEquals("1000", StringUtils.rightPad("1", 4, '0'));
}
分割字符串
// ["a","b","c"]
Assertions.assertEquals(Arrays.toString(new String[]{"a", "b", "c"}), Arrays.toString(StringUtils.split("a,b,c", ",")));
字符串比较
// true
Assertions.assertTrue(StringUtils.equals(null, null));
// false
Assertions.assertFalse(StringUtils.equals("null", null));
字符串已指定子字符串开头
@Test
void testStartWith() {
// true
Assertions.assertTrue(StringUtils.startsWith("hello,world", "hello"));
// false
Assertions.assertFalse(StringUtils.startsWith("你好,世界", "世界"));
}
数值工具类
转换为 int 类型
将字符串转换为 int
类型,toInt(String str)
在转换失败的时候会返回默认值 0
,如果需要指定默认值那么可以使用 toInt(final String str, final int defaultValue)
:
@Test
void testToInt() {
// 0
Assertions.assertEquals(0, NumberUtils.toInt("abc"));
// 0
Assertions.assertEquals(0, NumberUtils.toInt("01c"));
// 0
Assertions.assertEquals(0, NumberUtils.toInt("1a3"));
// 1
Assertions.assertEquals(1, NumberUtils.toInt("foo", 1));
// 11
Assertions.assertEquals(11, NumberUtils.toInt("11"));
// 11
Assertions.assertEquals(11, NumberUtils.toInt("011", 3));
}
数组
判断数组是否为空
@Test
void testIsEmpty() {
// true
Assertions.assertTrue(ArrayUtils.isEmpty(new Object[]{}));
// false
Assertions.assertFalse(ArrayUtils.isEmpty(new String[]{"foo"}));
}
日期
增加指定天数
除了增加指定的天数,common-lang3
还提供了:
addHours
:增加指定小时addMonths
:增加指定月数等...
@Test void testAddDay() { Date now = new Date(); Date tomorrow = DateUtils.addDays(now, 1); Assertions.assertEquals(1, Duration.ofMillis(tomorrow.getTime() - now.getTime()).toDays()); Assertions.assertEquals(Duration.ofDays(1).toMillis(), Duration.ofMillis(tomorrow.getTime() - now.getTime()).toMillis()); }
格式化日期
tring pattern = "yyyy-MM-dd HH:mm:ss";
Date d1 = DateUtils.parseDate("2022-10-22 00:00:00", pattern);
Assertions.assertEquals("2022-10-22 00:00:00", DateFormatUtils.format(d1, pattern));
判断是否为同一天
String parsePattern = "yyyy-MM-dd HH:mm:ss";
Date d1 = DateUtils.parseDate("2022-10-22 00:00:00", parsePattern);
Date d2 = DateUtils.parseDate("2022-10-22 23:59:59", parsePattern);
// true
Assertions.assertTrue(DateUtils.isSameDay(d1, d2));
d1 = DateUtils.parseDate("2022-10-23 00:00:00", parsePattern);
d2 = DateUtils.parseDate("2022-10-22 00:00:00", parsePattern);
// false
Assertions.assertFalse(DateUtils.isSameDay(d1, d2));
枚举
@Test
void testGetEnum() {
Assertions.assertThrowsExactly(IllegalArgumentException.class, () -> Season.valueOf("Spring"));
// 默认返回null,不抛出异常
Assertions.assertNull(EnumUtils.getEnum(Season.class, "spring"));
// 指定默认值
Assertions.assertEquals(Season.SPRING, EnumUtils.getEnumIgnoreCase(Season.class, "spring"));
// 忽略大小写匹配
Assertions.assertEquals(Season.SPRING, EnumUtils.getEnum(Season.class, "spring", Season.SPRING));
}
enum Season {
SPRING,
}
Guava
分割字符串
在了解 Guava
提供的字符串分割器之前,我们先来看看 Java
提供的字符串分隔有什么缺点,如下所示,输出的结果为:
",a,,b,".split(",")
"", "a", "", "b", ""
null, "a", null, "b", null
"a", null, "b"
"a", "b"
- 以上都不对
正确输出结果是 [, a, , b]
,答案是选项5:“以上都不对”。Splitter
不仅实现了字符串分隔,还提供了对应的修饰符,即对拆分结果进行处理,例如:
String str = "foo, bar ,,,baz";
// ["foo","bar","baz"]
Splitter.on(",")
.trimResults()
.omitEmptyStrings()
.splitToList(str);
// [上下上下左, 左, 右右]
str = "baba上下上下左a左b右右";
res = Splitter.on(CharMatcher.inRange('a', 'b'))
.trimResults()
.omitEmptyStrings()
.splitToList(str);
// [上下上下左, 左, 右右]
log.info("{}", res);
拆分器工厂
方法 | 描述 | 示例 |
---|---|---|
Splitter.on(char) | 按单个字符拆分 | Splitter.on(','); |
Splitter.on(CharMatcher) | 按字符匹配器拆分 | Splitter.on(CharMatcher.inRange('a', 'b')) |
Splitter.on(String) | 按字符串拆分 | Splitter.on(", ") |
Splitter.on(Pattern)或onPattern(String) | 按正则表达式拆分 | Splitter.on("\r?\n ") |
Splitter.fixedLength(int) | 按固定长度拆分;最后一段可能比给定长度短,但不会为空。 | Splitter.fixedLength(3) |
拆分器修饰符
方法 | 描述 |
---|---|
omitEmptyStrings() | 从结果中自动忽略空白字符串 |
trimResults() | 移除结果字符串的首位空白字符 |
trimResults(CharMatcher) | 给定匹配器,移除结果字符串的首位匹配字符 |
limit(int) | 限制拆分出的字符串数量 |
不可变集合
public static final ImmutableSet<String> COLOR_NAMES = ImmutableSet.of(
"red",
"orange",
"yellow",
"green",
"blue",
"purple");
class Foo {
Set<Bar> bars;
Foo(Set<Bar> bars) {
this.bars = ImmutableSet.copyOf(bars); // defensive copy!
}
}
不可变对象有很多的优点:
- 当对象被不可信的库调用时,不可变形式是安全的;
- 不可变对象被多个线程调用时,不存在竞态条件问题
- 不可变集合不需要考虑变化,因此可以节省时间和空间。所有不可变的集合都比它们的可变形式有更好的内存利用率(分析和测试细节);
- 不可变对象因为有固定不变,可以作为常量来安全使用。
使用不可变集合
不可变集合可以用如下多种方式创建:
copyOf
:ImmutableList.copyOf
of
:ImmutableList.of("a","b","c")
Builder
工具,例如:
public static final ImmutableSet<Color> GOOGLE_COLORS =
ImmutableSet.<Color>builder()
.addAll(WEBSAFE_COLORS)
.add(new Color(0, 191, 255))
.build();
连接字符串
@Test
void testJoin() {
// foo,bar
Assertions.assertEquals("foo,bar", Joiner.on(',').join(ImmutableList.of("foo", "bar")));
// foo
Assertions.assertEquals("foo", Joiner.on(',').skipNulls().join("foo", null));
// foo,empty
Assertions.assertEquals("foo,empty", Joiner.on(',').useForNull("empty").join("foo", null));
// 抛出空指针异常
Assertions.assertThrowsExactly(NullPointerException.class, () -> Joiner.on(',').join("foo", null));
}
警告:joiner实例总是不可变的。用来定义joiner目标语义的配置方法总会返回一个新的joiner实例。这使得joiner实例都是线程安全的,你可以将其定义为static final常量。
Strings
将 null
转换为空字符串:
Assertions.assertEquals("", Strings.nullToEmpty(null));
将空字符串转换为 null
:
Assertions.assertEquals(null, Strings.emptyToNull(""));
Assertions.assertEquals(null, Strings.emptyToNull(null));
CharMatcher
String noControl = CharMatcher.JAVA_ISO_CONTROL.removeFrom(string); //移除control字符
String theDigits = CharMatcher.DIGIT.retainFrom(string); //只保留数字字符
String spaced = CharMatcher.WHITESPACE.trimAndCollapseFrom(string, ' ');
//去除两端的空格,并把中间的连续空格替换成单个空格
String noDigits = CharMatcher.JAVA_DIGIT.replaceFrom(string, "*"); //用*号替换所有数字
String lowerAndDigit = CharMatcher.JAVA_DIGIT.or(CharMatcher.JAVA_LOWER_CASE).retainFrom(string);
// 只保留数字和小写字母
Spring
判断集合是否为空
@Test
void testIsEmpty() {
Assertions.assertTrue(CollectionUtils.isEmpty((List<?>) null));
Assertions.assertTrue(CollectionUtils.isEmpty((Set<?>) null));
Assertions.assertTrue(CollectionUtils.isEmpty((Map<?, ?>) null));
Assertions.assertTrue(CollectionUtils.isEmpty(Collections.emptyList()));
Assertions.assertTrue(CollectionUtils.isEmpty(Collections.emptySet()));
Assertions.assertTrue(CollectionUtils.isEmpty(Collections.emptyMap()));
Assertions.assertTrue(CollectionUtils.isEmpty(List.of()));
Assertions.assertTrue(CollectionUtils.isEmpty(Set.of()));
Assertions.assertTrue(CollectionUtils.isEmpty(Map.of()));
List<Object> list = new LinkedList<>();
list.add(new Object());
Assertions.assertFalse(CollectionUtils.isEmpty(list));
Assertions.assertFalse(CollectionUtils.isEmpty(List.of("foo")));
Map<String, String> map = new HashMap<>();
map.put("foo", "bar");
Assertions.assertFalse(CollectionUtils.isEmpty(map));
Assertions.assertFalse(CollectionUtils.isEmpty(Map.of("foo", "bar")));
}
获取集合的第一个元素
@Test
void testFirstElement() {
Assertions.assertNull(CollectionUtils.firstElement((Set<?>) null));
Assertions.assertNull(CollectionUtils.firstElement((List<?>) null));
List<String> list = new ArrayList<>();
list.add(null);
// null
Assertions.assertNull(CollectionUtils.firstElement(list));
list = new ArrayList<>();
list.add("foo");
// foo
Assertions.assertEquals("foo", CollectionUtils.firstElement(list));
list = List.of("foo", "bar");
// foo
Assertions.assertEquals("foo", CollectionUtils.firstElement(list));
Set<String> set = new TreeSet<>();
set.add("b");
set.add("a");
// a
Assertions.assertEquals("a", CollectionUtils.firstElement(set));
// b
set = new TreeSet<>(Comparator.reverseOrder());
set.add("b");
set.add("a");
Assertions.assertEquals("b", CollectionUtils.firstElement(set));
}
获取集合的最后一个元素
@Test
void testLastElement() {
Assertions.assertNull(CollectionUtils.lastElement((Set<?>) null));
Assertions.assertNull(CollectionUtils.lastElement((List<?>) null));
List<String> list = new ArrayList<>();
list.add(null);
Assertions.assertNull(CollectionUtils.lastElement(list));
list = new ArrayList<>();
list.add("foo");
list.add("bar");
// bar
Assertions.assertEquals("bar", CollectionUtils.lastElement(list));
list = List.of("foo", "bar");
Assertions.assertEquals("bar", CollectionUtils.lastElement(list));
Set<String> set = new TreeSet<>();
set.add("b");
set.add("a");
// b
Assertions.assertEquals("b", CollectionUtils.lastElement(set));
set = new TreeSet<>(Comparator.reverseOrder());
set.add("b");
set.add("a");
// a
Assertions.assertEquals("a", CollectionUtils.lastElement(set));
}
对象属性拷贝
添加一个测试对象:
class User {
private String name;
private String email;
// 忽略getXxx和setXxx方法
@Test
void testCopyProperties() {
User user = new User();
user.setName("foo");
user.setEmail("bar");
User target = new User();
// 拷贝属性
BeanUtils.copyProperties(user, target, "email");
Assertions.assertEquals("foo", target.getName());
Assertions.assertNull(target.getEmail());
}
命名的 ThreadLocal
@Test
void testNamedThreadLocal() {
NamedThreadLocal<String> threadLocal = new NamedThreadLocal<>("task");
Assertions.assertEquals("task", threadLocal.toString());
}
判断对象是否相等
@Test
void testNullSafeEquals() {
Assertions.assertTrue(ObjectUtils.nullSafeEquals(null, null));
Assertions.assertTrue(ObjectUtils.nullSafeEquals("a", "a"));
Assertions.assertTrue(ObjectUtils.nullSafeEquals(Optional.of("a"), Optional.of("a")));
}
判断对象是否为空
@Test
void testIsEmpty() {
Assertions.assertTrue(ObjectUtils.isEmpty((Object) null));
Assertions.assertTrue(ObjectUtils.isEmpty(Optional.empty()));
Assertions.assertTrue(ObjectUtils.isEmpty(""));
Assertions.assertTrue(ObjectUtils.isEmpty(new String[]{}));
Assertions.assertTrue(ObjectUtils.isEmpty(Collections.emptyList()));
Assertions.assertTrue(ObjectUtils.isEmpty(Collections.emptyMap()));
}
资源工具类
有时候我们需要加载 classpath
目录下的资源,例如:
File file = new File(ResourceUtilsTests.class.getClassLoader().getResource("log4j2.xml").toURI());
Assertions.assertEquals("log4j2.xml", file.getName());
使用 Spring
的 ResourceUtils
只需要这么写:
File file = ResourceUtils.getFile(ResourceUtils.CLASSPATH_URL_PREFIX + "log4j2.xml");
Assertions.assertEquals("log4j2.xml", file.getName());
计时器
@Test
void testStopWatch() throws InterruptedException {
// 创建一个计时器(秒表)
StopWatch stopWatch = new StopWatch();
// 开始计时
stopWatch.start();
Thread.sleep(Duration.ofSeconds(1).toMillis());
// 停止计时
stopWatch.stop();
// 获取总耗时(毫秒)
// 1005ms.
log.info("{}ms.", stopWatch.getTotalTimeMillis());
// 1s.
log.info("{}s.", Duration.ofMillis(stopWatch.getTotalTimeMillis()).toSeconds());
}
UriComponentsBuilder
有时候我们需要在服务端手动发送请求,在请求 url
我们使用字符串拼接的方式,Spring
提供了UriComponentsBuilder
能让我们更加语意化来构建一个请求url
,而且还会自动对url
进行编码:
@Test
void testFromUriString() {
String uri = UriComponentsBuilder
.fromUriString("/coffee/{foo}/{id}/like")
.build("aa", "bb")
.toString();
Assertions.assertEquals("/coffee/aa/bb/like", uri);
uri = UriComponentsBuilder
.fromUriString("http://localhost:8080/coffe/{id}")
.encode()
.build(1).toString();
Assertions.assertEquals("http://localhost:8080/coffe/1", uri);
uri = UriComponentsBuilder
.fromUriString("http://localhost:8080/coffee?name={name}")
.build(" ").toString();
Assertions.assertEquals("http://localhost:8080/coffee?name=%20",uri);
}
hutool
校验
@Test
void testIsCitizenId() {
// 校验是否为身份证
Assertions.assertTrue(Validator.isCitizenId("110101199003074477"));
// 15位身份证号码验证
Assertions.assertTrue(Validator.isCitizenId("410001910101123"));
// 10位身份证号码验证
Assertions.assertTrue(Validator.isCitizenId("U193683453"));
}
@Test
void testIsMobile() {
// 校验是否为手机号
Assertions.assertTrue(Validator.isMobile("13900221432"));
Assertions.assertTrue(Validator.isMobile("015100221432"));
Assertions.assertTrue(Validator.isMobile("+8618600221432"));
}
@Test
void testIsPlateNumber() {
// 校验是否为车牌号
Assertions.assertTrue(Validator.isPlateNumber("粤BA03205"));
Assertions.assertTrue(Validator.isPlateNumber("闽20401领"));
}
emoji
@Test
void testToUnicode() {
String unicode = EmojiUtil.toUnicode(":smile:");
Assertions.assertEquals("😄", unicode);
}
@Test
void testToAlias() {
Assertions.assertEquals(":smile:", EmojiUtil.toAlias("😄"));
}
@Test
void testToHtml() {
String html = EmojiUtil.toHtml("😄");
Assertions.assertEquals("😄", html);
}
拼音
引入依赖:
<dependency>
<groupId>io.github.biezhi</groupId>
<artifactId>TinyPinyin</artifactId>
<version>2.0.3.RELEASE</version>
</dependency>
获取拼音:
@Test
void testGetPinyin() {
Assertions.assertEquals("ceng", PinyinUtil.getPinyin("曾"));
Assertions.assertEquals("f o o", PinyinUtil.getPinyin("foo"));
Assertions.assertThrowsExactly(NullPointerException.class, () -> PinyinUtil.getPinyin(null));
Assertions.assertEquals(" ", PinyinUtil.getPinyin(" "));
// ? ?
log.info("{}", PinyinUtil.getPinyin("🐛"));
Assertions.assertEquals("! # ¥ % ( # ) @", PinyinUtil.getPinyin("!#¥%(#)@"));
}
压缩
转换
@Test
void testDigitToChinese() {
Assertions.assertEquals("零元零壹分",Convert.digitToChinese(0.01));
}
二维码
@Test
void testGenerate() {
// 生成二维码
final BufferedImage image = QrCodeUtil.generate("https://hutool.cn/", 300, 300);
Assertions.assertNotNull(image);
}
SpringUtil
SpringUtil
实现了通过 @EnalbeAutoConfiguuration
自动装配 Bean
,文件 spring.factories
定义如下:
# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
cn.hutool.extra.spring.SpringUtil
// 获取bean
final Demo2 testDemo = SpringUtil.getBean("testDemo");
版本比较
@Test
void testCompare() {
Assertions.assertEquals(-1, VersionComparator.INSTANCE.compare("1.12.1", "1.12.1c"));
Assertions.assertEquals(1, VersionComparator.INSTANCE.compare("V0.0.20170102", "V0.0.20170101"));
}
身份证
private static final String ID_18 = "321083197812162119";
private static final String ID_15 = "150102880730303";
/**
* 根据身份编号获取生日,只支持15或18位身份证号码.
*/
@Test
void testGetBirthByIdCard() {
Assertions.assertEquals(IdcardUtil.getBirthByIdCard(ID_18), "19781216");
Assertions.assertEquals(IdcardUtil.getBirthByIdCard(ID_15), "19880730");
}
打码/信息脱敏
void testIdCardNum() {
Assertions.assertEquals("5***************1X",
DesensitizedUtil.idCardNum("51343620000320711X", 1, 2));
}
@Test
void testMobilePhone() {
Assertions.assertEquals("180****1999", DesensitizedUtil.mobilePhone("18049531999"));
}
@Test
void testPassword() {
Assertions.assertEquals("**********", DesensitizedUtil.password("1234567890"));
}
@Test
void testEmail() {
Assertions.assertEquals("d********@126.com", DesensitizedUtil.email("duandazhi@126.com"));
Assertions.assertEquals("d********@gmail.com.cn", DesensitizedUtil.email("duandazhi@gmail.com.cn"));
Assertions.assertEquals("d*************@gmail.com.cn", DesensitizedUtil.email("duandazhi-jack@gmail.com.cn"));
}
加密
引入依赖:
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15to18</artifactId>
<version>1.69</version>
</dependency>
SM4 对称加密:
String content = "test中文"; SymmetricCrypto sm4 = SmUtil.sm4();
String encryptHex = sm4.encryptHex(content);
String decryptStr = sm4.decryptStr(encryptHex, CharsetUtil.CHARSET_UTF_8);
JDK
Collections
返回空数组:
@Test
void testEmptyList() {
Assertions.assertTrue(Collections.emptyList().isEmpty());
}
Arrays
打印数组信息,方便debug:
@Test
void testToString() {
Assertions.assertEquals("[a, b, c]",Arrays.toString(new String[]{"a","b","c"}));
Assertions.assertEquals("null",Arrays.toString((String[]) null));
}
Duration
有时候我们传递一些时间参数,单位可能是秒、毫米、分钟、小时等,例如线程睡眠时间,我们可以使用 Duration
来语意化我们的代码:
@Test
void test() throws InterruptedException {
Thread.currentThread().sleep(Duration.ofSeconds(1).toMillis());
}
StandardCharsets
我们有时候需要用到字符集,例如:
URLEncoder
InputStreamReader
IOUtils.toString
可以使用 StandardCharsets
,例如:
IOUtils.toString(new ClassPathResource("log4j2.xml").getInputStream(), StandardCharsets.UTF_8)
Objects
对象 equals
:
@Test
void testEquals() {
Assertions.assertTrue(Objects.equals(null, null));
Assertions.assertFalse(Objects.equals("a", "b"));
}
避免空指针获取 hashCode
:
@Test
void testHashCode() {
Assertions.assertEquals(0, Objects.hashCode(null));
Assertions.assertEquals("a".hashCode(), Objects.hashCode("a"));
}
null
转默认值:
@Test
void testRequireNonNullElse() {
Assertions.assertEquals("a", Objects.requireNonNullElse(null, "a"));
}
判断对象不为空,配合 Stream
:
@Test
void testNonNull() {
List<String> names = Lists.newArrayList("foo", null);
names = names.stream()
.filter(Objects::nonNull)
.collect(Collectors.toList());
Assertions.assertEquals(names, List.of("foo"));
}
Optional
@Test
void testOptional() {
// 创建一个 Optional 对象,不允许为空
Optional<String> optional = Optional.of("a");
// 获取值,如果值为空抛出 NoSuchElementException 异常
Assertions.assertEquals("a", optional.get());
// 判断Optional的值是否为空
Assertions.assertFalse(optional.isEmpty());
// 判断Optional的值是否不为空
Assertions.assertTrue(optional.isPresent());
// 创建一个 Optional 对象,允许为 null
optional = Optional.ofNullable(null);
// 获取值,如果值为空抛出 NoSuchElementException 异常
Assertions.assertThrowsExactly(NoSuchElementException.class, optional::get);
// 判断Optional的值是否为空
Assertions.assertTrue(optional.isEmpty());
// 判断Optional的值是否不为空
Assertions.assertFalse(optional.isPresent());
// 创建一个空的Optional对象
optional = Optional.empty();
// 获取值,如果值为空抛出 NoSuchElementException 异常
Assertions.assertThrowsExactly(NoSuchElementException.class, optional::get);
// 判断Optional的值是否为空
Assertions.assertTrue(optional.isEmpty());
// 判断Optional的值是否不为空
Assertions.assertFalse(optional.isPresent());
}
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来通知其他用户。