java.lang.Objects / org.apache.commons.lang.ObjectUtils;

boolean isNull(Object obj); 判断null

boolean equals(Object a, Object b); 等值判断

int hashCode(Object o); 哈希值

String toString(Object o, String defaultValue);

java.util.Collections

void sort(List list); 排序

? max(collection); 最大值

? min(collection); 最小值

void shuffle(list); 洗牌，随机重排序

CollectionUtils

org.apache.commons.collections.CollectionUtils

boolean isEmpty(collection); 非空判断

void addAll(Collection collection, Iterator iterator); 批量添加集合(Iterator)

void addAll(Collection collection, Enumeration enumeration); 批量添加集合(Enumeration)

void addAll(Collection collection, Object[] elements); 批量添加集合(数组)

DateFormatUtils 时间格式化

String format(Date date, String pattern);

String format(Calendar calendar, String pattern);

String format(long millis, String pattern);

DateUtils 时间操作

时间计算

Date addYears(Date date, int amount)

Date addMonths(Date date, int amount)

Date addWeeks(Date date, int amount)

Date addDays(Date date, int amount)

Date addHours(Date date, int amount)

Date addMinutes(Date date, int amount)

Date addSeconds(Date date, int amount)

Date addMilliseconds(Date date, int amount)

Date setYears(Date date, int amount)

Date setMonths(Date date, int amount)

Date setDays(Date date, int amount)

Date setHours(Date date, int amount)

Date setMinutes(Date date, int amount)

Date setSeconds(Date date, int amount)

Date setMilliseconds(Date date, int amount)

时间范围计算

Date ceiling(Date date, inti field); //根据时间单位字段，计算最大值，如 "2017-12-07 16:46:59"，field为Calendar.DATE，计算出的Date为：2017-12-08 00:00:00

Date ceiling1 = DateUtils.ceiling(new Date(), Calendar.YEAR);

Date ceiling2 = DateUtils.ceiling(new Date(), Calendar.MONTH);

Date ceiling3 = DateUtils.ceiling(new Date(), Calendar.DATE);

Date ceiling4 = DateUtils.ceiling(new Date(), Calendar.HOUR);

// 输出结果为

2018-01-01 00:00:00

2018-01-01 00:00:00

2017-12-08 00:00:00

2017-12-07 17:00:00

时间比较

boolean isSameDay(Date date1, Date date2);

parse 字符串转化为时间

DateUtils.parseDate("2017-12-07",new String[]{"yyyy-MM-dd"})