Java常用工具类

本文主要是根据 朱小厮的博客 《代码量减少90%，Java程序员必会的工具库》一文整理而来。

 想深入了解可阅读其原文：代码量减少90%，Java程序员必会的工具库_朱小厮的博客-优快云博客

1、jdk自带工具类

2、2. apache commons工具类库

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

        主要操作字符串判空，字符串拼接，日期格式化。

3、commons-collections 集合工具类

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-collections4</artifactId>
    <version>4.4</version>
</dependency>

         主要操作集合

4、common-beanutils 操作对象 

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

User user = new User();
BeanUtils.setProperty(user, "id", 1);
BeanUtils.setProperty(user, "name", "yideng");
System.out.println(BeanUtils.getProperty(user, "name")); // 输出 yideng
System.out.println(user); // 输出 {"id":1,"name":"yideng"}

 5 commons-io 文件流处理

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.8.0</version>
</dependency>

 6.Google Guava 工具类库

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>30.1.1-jre</version>
</dependency>

7、 毫秒值转时分秒

public class CommonUtils {
    public static String formatTime(Long ms) {
        Integer ss = 1000;
        Integer mi = ss * 60;
        Integer hh = mi * 60;
        Integer dd = hh * 24;

        Long day = ms / dd;
        Long hour = (ms - day * dd) / hh;
        Long minute = (ms - day * dd - hour * hh) / mi;
        Long second = (ms - day * dd - hour * hh - minute * mi) / ss;
        Long milliSecond = ms - day * dd - hour * hh - minute * mi - second * ss;

        StringBuffer sb = new StringBuffer();
        if(day > 0) {
            sb.append(day+"day");
        }
        if(hour > 0) {
            sb.append(hour+"h");
        }
        if(minute > 0) {
            sb.append(minute+"min");
        }
        if(second > 0) {
            sb.append(second+"s");
        }
        if(milliSecond > 0) {
            sb.append(milliSecond+"ms");
        }
        return sb.toString();
    }
}