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头图

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-lang3StringUtils

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:

  1. addHours:增加指定小时
  2. addMonths:增加指定月数
  3. 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(",")
  1. "", "a", "", "b", ""
  2. null, "a", null, "b", null
  3. "a", null, "b"
  4. "a", "b"
  5. 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:

  1. 当对象被不可信的库调用时,不可变形式是安全的;
  2. 不可变对象被多个线程调用时,不存在竞态条件问题
  3. 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);
  4. 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:

  1. copyOfImmutableList.copyOf
  2. ofImmutableList.of("a","b","c")
  3. 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

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 SpringResourceUtils 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("&#x1f604;", 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:

  1. URLEncoder
  2. InputStreamReader
  3. 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());
}

async_wait
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