Java系列 - 工具类提效

有很多现成的工具包可以加速开发，简化代码书写，将其分门别类归纳.

使用： StringUtils.isNotBlank(“ifredom”);

    org.apache.commons
    >commons-lang3
    3.12.0

• 1.java.util包下的 Collections 类

List list = new ArrayList<>();
list.add(2);
list.add(1);
list.add(3);

Collections.sort(list);// 升序
Collections.reverse(list);// 降序

Integer max = Collections.max(list);// 获取最大值
Integer min = Collections.min(list);// 获取最小值

List integers = Collections.synchronizedList(list);// 将ArrayList转换成线程安全集合

Collections.emptyList();// 空集合

int i = Collections.binarySearch(list, 3);// 二分查找

List unmodifiablIntegers = Collections.unmodifiableList(list); // 转换成不可修改集合

• 2.org.apache.commons 包下的 ColletcionUtils（不推介使用spring框架提供的collections）

    org.apache.directory.studio
    >org.apache.commons.collections
    3.2.1

使用：

List list = new ArrayList<>();
list.add(2);
list.add(1);
list.add(3);

List list2 = new ArrayList<>();
list2.add(2);
list2.add(4);

if (CollectionUtils.isEmpty(list)) {
    System.out.println("集合为空");
}

if (CollectionUtils.isNotEmpty(list)) {
    System.out.println("集合不为空");
}

//获取并集
Collection unionList = CollectionUtils.union(list, list2);
System.out.println(unionList);

//获取交集
Collection intersectionList = CollectionUtils.intersection(list, list2);
System.out.println(intersectionList);

//获取交集的补集
Collection disjunctionList = CollectionUtils.disjunction(list, list2);
System.out.println(disjunctionList);

//获取差集
Collection subtractList = CollectionUtils.subtract(list, list2);
System.out.println(subtractList);

Integer integer = new Integer(1);

if (Objects.isNull(integer)) {
    System.out.println("对象为空");
}

if (Objects.nonNull(integer)) {
    System.out.println("对象不为空");
}

与字符工具类一样，推介使用： commons-lang3

布尔的包装类：Boolean， 它有三种值：null、true、false

    org.apache.commons
    >commons-lang3
    3.12.0

Boolean aBoolean = new Boolean(true);
Boolean aBoolean1 = null;

// 判断true或false
System.out.println(BooleanUtils.isTrue(aBoolean));
System.out.println(BooleanUtils.isFalse(aBoolean));

// 判断不为true或不为false
System.out.println(BooleanUtils.isNotTrue(aBoolean));
System.out.println(BooleanUtils.isNotTrue(aBoolean1));

// 转换成数字
System.out.println(BooleanUtils.toInteger(aBoolean));
System.out.println(BooleanUtils.toInteger(aBoolean1));

// Boolean转换成布尔值
System.out.println(BooleanUtils.toBoolean(aBoolean));
System.out.println(BooleanUtils.toBoolean(aBoolean1));
System.out.println(BooleanUtils.toBooleanDefaultIfNull(aBoolean1, false));

    org.apache.directory.studio
    >org.apache.commons.io
    2.4

主要常用到这3个类

• org.apache.commons.io.IOUtils
• org.apache.commons.io.FilenameUtils
• org.apache.commons.io.FileUtils

public void upload(File file) {


	// 读取文件
	String str = IOUtils.toString(new FileInputStream("/temp/a.txt"), StandardCharsets.UTF_8);
	System.out.println(str);

	// 写入文件
	String str = "abcde";
	IOUtils.write(str, new FileOutputStream("/temp/b.tx"), StandardCharsets.UTF_8);

	// 文件拷贝
	IOUtils.copy(new FileInputStream("/temp/a.txt"), new FileOutputStream("/temp/b.txt"));

	// 读取文件内容到字节数组
	byte[] bytes = IOUtils.toByteArray(new FileInputStream("/temp/a.txt"));



	String originalFilename = file.getOriginalFilename();

	// 获取文件后缀
	String suffix = FilenameUtils.getExtension(originalFilename)
	// 获取返回文件名，不包含后缀
	String filename = FilenameUtils.getBaseName(originalFilename);
}

• org.springframework.util.ReflectionUtils

@Test
public void reflectionTest() {
	// 获取方法
	Method method = ReflectionUtils.findMethod(User.class, "getId");
	// 获取属性
	Field field = ReflectionUtils.findField(User.class, "id");

	// 执行方法
    User user = new User();			
    user.setId(1L);
    Long id = (Long) ReflectionUtils.invokeMethod(method, user);

	// 判断字段是否常量
	Field field = ReflectionUtils.findField(User.class, "id");
	System.out.println(ReflectionUtils.isPublicStaticFinal(field));

}

• org.springframework.beans.BeanUtils
• Cglib的 net.sf.cglib.beans.BeanCopier

使用BeanUtils：

User user1 = new User();
user1.setId(1L);
user1.setName("ifredom");
user1.setAddress("石家庄");

User user2 = new User();

// 拷贝对象
BeanUtils.copyProperties(user1, user2);
System.out.println(user2);

// 实例化某个类
User user = BeanUtils.instantiateClass(User.class);

// 获取指定类的指定方法
Method declaredMethod = BeanUtils.findDeclaredMethod(User.class, "getId");
System.out.println(declaredMethod.getName());

// 获取指定方法的参数
Method declaredMethod = BeanUtils.findDeclaredMethod(User.class, "getId");
PropertyDescriptor propertyForMethod = BeanUtils.findPropertyForMethod(declaredMethod);
System.out.println(propertyForMethod.getName());

使用 BeanCopier：

@Test
public void normalCopyTest() {

    final BeanCopier beanCopier = BeanCopier.create(User.class, UserDto.class, false);

    User user = new User();
    user.setAge(18);
    user.setName("ifredom");

    UserDto userDto = new UserDto();

    beanCopier.copy(user, userDto, null);

    Assert.assertEquals(10, userDto.getAge());
    Assert.assertEquals("zhangsan", userDto.getName());
}

org.apache.commons.codec.digest.DigestUtils

• md5Hex：MD5加密，返回32位字符串
• sha1Hex：SHA-1加密
• sha256Hex：SHA-256加密
• sha512Hex：SHA-512加密
• md5：MD5加密，返回16位字符串

• java.util.Base64
• org.springframework.util.Base64Utils

• org.springframework.http.HttpStatus

 
     com.github.binarywang
     >weixin-java-miniapp
     4.3.0
 
 
     com.github.binarywang
     >weixin-java-common
     4.3.0
 
 
     com.github.binarywang
     >weixin-java-pay
     4.3.0
 

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