优秀代码

2.1.3 重复拼接字符串

String str = StringUtils.repeat("ab", 2);  
System.out.println(str); // 输出abab

2.1.4 格式化日期

再也不用手写SimpleDateFormat格式化了

// Date类型转String类型  
String date = DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss");  
System.out.println(date); // 输出 2021-05-01 01:01:01  
// String类型转Date类型  
Date date = DateUtils.parseDate("2021-05-01 01:01:01", "yyyy-MM-dd HH:mm:ss");  
// 计算一个小时后的日期  
Date date = DateUtils.addHours(new Date(), 1);

2.1.5 包装临时对象

当一个方法需要返回两个及以上字段时，我们一般会封装成一个临时对象返回，现在有了Pair和Triple就不需要了

// 返回两个字段  
ImmutablePair<Integer, String> pair = ImmutablePair.of(1, "yideng");  
System.out.println(pair.getLeft() + "," + pair.getRight()); // 输出 1,yideng  
// 返回三个字段  
ImmutableTriple<Integer, String, Date> triple = ImmutableTriple.of(1, "yideng", new Date());  
System.out.println(triple.getLeft() + "," + triple.getMiddle() + "," + triple.getRight()); // 输出 1,yideng,Wed Apr 07 23:30:00 CST 2021

2.2 commons-collections 集合工具类

Maven依赖是：

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

2.2.1 集合判空

封装了集合判空的方法，以下是源码：

public static boolean isEmpty(final Collection<?> coll) {  
    return coll == null || coll.isEmpty();  
}  
public static boolean isNotEmpty(final Collection<?> coll) {  
    return !isEmpty(coll);  
}  
// 两个集合取交集  
Collection<String> collection = CollectionUtils.retainAll(listA, listB);  
// 两个集合取并集  
Collection<String> collection = CollectionUtils.union(listA, listB);  
// 两个集合取差集  
Collection<String> collection = CollectionUtils.subtract(listA, listB);

2.3 common-beanutils 操作对象

Maven依赖：

<dependency>  
    <groupId>commons-beanutils</groupId>  
    <artifactId>commons-beanutils</artifactId>  
    <version>1.9.4</version>  
</dependency>  
public class User {  
    private Integer id;  
    private String name;  
}

设置对象属性

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"}

对象和map互转

// 对象转map  
Map<String, String> map = BeanUtils.describe(user);  
System.out.println(map); // 输出 {"id":"1","name":"yideng"}  
// map转对象  
User newUser = new User();  
BeanUtils.populate(newUser, map);  
System.out.println(newUser); // 输出 {"id":1,"name":"yideng"}

2.4 commons-io 文件流处理

Maven依赖：

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

文件处理

File file = new File("demo1.txt");  
// 读取文件  
List<String> lines = FileUtils.readLines(file, Charset.defaultCharset());  
// 写入文件  
FileUtils.writeLines(new File("demo2.txt"), lines);  
// 复制文件  
FileUtils.copyFile(srcFile, destFile);

3. Google Guava 工具类库

Maven依赖：

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

3.1 创建集合

List<String> list = Lists.newArrayList();  
List<Integer> list = Lists.newArrayList(1, 2, 3);  
// 反转list  
List<Integer> reverse = Lists.reverse(list);  
System.out.println(reverse); // 输出 [3, 2, 1]  
// list集合元素太多，可以分成若干个集合，每个集合10个元素  
List<List<Integer>> partition = Lists.partition(list, 10);  
Map<String, String> map = Maps.newHashMap();  
Set<String> set = Sets.newHashSet();

3.2 黑科技集合

3.2.1 Multimap 一个key可以映射多个value的HashMap

Multimap<String, Integer> map = ArrayListMultimap.create();  
map.put("key", 1);  
map.put("key", 2);  
Collection<Integer> values = map.get("key");  
System.out.println(map); // 输出 {"key":[1,2]}  
// 还能返回你以前使用的臃肿的Map  
Map<String, Collection<Integer>> collectionMap = map.asMap();

多省事，多简洁，省得你再创建 Map

3.2.2 BiMap 一种连value也不能重复的HashMap

BiMap<String, String> biMap = HashBiMap.create();  
// 如果value重复，put方法会抛异常，除非用forcePut方法  
biMap.put("key","value");  
System.out.println(biMap); // 输出 {"key":"value"}  
// 既然value不能重复，何不实现个翻转key/value的方法，已经有了  
BiMap<String, String> inverse = biMap.inverse();  
System.out.println(inverse); // 输出 {"value":"key"}

这其实是双向映射，在某些场景还是很实用的。

3.2.3 Table 一种有两个key的HashMap

// 一批用户，同时按年龄和性别分组  
Table<Integer, String, String> table = HashBasedTable.create();  
table.put(18, "男", "yideng");  
table.put(18, "女", "Lily");  
System.out.println(table.get(18, "男")); // 输出 yideng  
// 这其实是一个二维的Map，可以查看行数据  
Map<String, String> row = table.row(18);  
System.out.println(row); // 输出 {"男":"yideng","女":"Lily"}  
// 查看列数据  
Map<Integer, String> column = table.column("男");  
System.out.println(column); // 输出 {18:"yideng"}

3.2.4 Multiset 一种用来计数的Set

Multiset<String> multiset = HashMultiset.create();  
multiset.add("apple");  
multiset.add("apple");  
multiset.add("orange");  
System.out.println(multiset.count("apple")); // 输出 2  
// 查看去重的元素  
Set<String> set = multiset.elementSet();  
System.out.println(set); // 输出 ["orange","apple"]  
// 还能查看没有去重的元素  
Iterator<String> iterator = multiset.iterator();  
while (iterator.hasNext()) {  
    System.out.println(iterator.next());  
}  
// 还能手动设置某个元素出现的次数  
multiset.setCount("apple", 5);

https://www.cnblogs.com/liyihua/p/12286086.html

    @Override
    public Map<String, ?> executeCancel(OdoOperateVo vo) {
        return operate(vo, null, o -> o.setOperateType(JdiTransactionOperateTypeEnum.ODO_HOLD_CANCEL.type));
    }
    @Override
    public Map<String, ?> executeConfirm(OdoOperateVo vo) {
        return operate(vo, o -> {
            // 检查是否有商品没有销售价
            JdiSaleOrderQueryVo queryVo = new JdiSaleOrderQueryVo();
            queryVo.setShopId(vo.getShopId());
            queryVo.setStoreId(vo.getStoreId());
            queryVo.setSaleOrderNo(o.getOriginOrderNo());
            // 返回true表示有无价格商品
            RemoteResultBean<Boolean> r = saleOrderManService.hasNullSalePriceGoods(queryVo);
            if (!r.isSuccess() || r.getContent()) {
                throw new UnsupportedOperationException("销售单[" + o.getOriginOrderNo() + "]存在商品无销售价的情况");
            }
            return true;
        }, o -> {
            o.setOperateType(JdiTransactionOperateTypeEnum.ODO_NORMAL.type);
            o.setChangedQuantity(o.getHoldQuantity());
        });
    }
    /**
     * operate
     * @param vo
     * @param filter
     * @param consumer
     * @return
     */
    private Map<String, ?> operate(OdoOperateVo vo, Predicate<JdiOdoHeader> filter, Consumer<JdiStockChangeDto> consumer) {
        JdiOdoHeader odoHeader = odoHeaderService.findByOdoNo(vo.getOdoNo(), vo.getWarehouseNo(), vo.getShopId());
        if (odoHeader == null) {
            throw new EntityNotFoundException("JdiOutboundService.exec", vo.getWarehouseNo() + ": 查询的出库单[" + vo.getOdoNo() + "]不存在");
        }
        // 状态检查
        if (odoHeader.getOdoStatus() == null || JdiOdoStatusEnum.OUTING.getValue() != odoHeader.getOdoStatus()) {
            throw new UnsupportedOperationException("发货单[" + vo.getOdoNo() + "]当前状态不是“待发货确认”无法执行关单操作！");
        }
        // 特殊检查
        if (filter != null && !filter.test(odoHeader)) {
            return Collections.emptyMap();
        }
        List<JdiOdoDetail> list = odoDetailService.queryByOdoNo(vo.getOdoNo(), vo.getWarehouseNo(), vo.getShopId());
        JdiStockTransactionLog queryVo = new JdiStockTransactionLog();
        queryVo.setShopId(vo.getShopId());
        queryVo.setStoreId(vo.getStoreId());
        queryVo.setWarehouseNo(vo.getWarehouseNo());
        queryVo.setDocNo(odoHeader.getOdoNo());
        queryVo.setOperateType(JdiTransactionOperateTypeEnum.ODO_HOLD.type);
        JdiStockQueryVo stockQueryVo = new JdiStockQueryVo();
        stockQueryVo.setShopId(vo.getShopId());
        stockQueryVo.setStoreId(vo.getStoreId());
        JdiOdoVo odoVo = AgileConvert.convert(vo, JdiOdoVo.class);
        boolean hasConsumer = consumer != null;
        // 修改时间
        Date date = new Date();
        // 实际发货数量
        BigDecimal totalShipped = BigDecimal.ZERO;
        // 状态
        int status = vo.getOperate() == OdoOperateVo.Operate.CONFIRM ? JdiOdoStatusEnum.FINISHED.getValue()
                : JdiOdoStatusEnum.CANCEL.getValue();
        List<JdiStockTransactionLog> logList = new ArrayList<>();
        List<JdiStockAveragePriceChangeVo> priceChangeVoList = new ArrayList<>();
        for (JdiOdoDetail detail : list) {
            queryVo.setDocDetailNo(detail.getOdoDetailNo());
            queryVo.setSkuId(detail.getSkuId());
            List<JdiStockTransactionLog> logs = logService.queryLogList(queryVo);
            // 实际发货数量
            BigDecimal shipped = BigDecimal.ZERO;
            for (JdiStockTransactionLog log : logs) {
                stockQueryVo.setWarehouseNo(log.getWarehouseNo());
                stockQueryVo.setPartitionNo(log.getPartitionNo());
                stockQueryVo.setLocationNo(log.getLocationNo());
                stockQueryVo.setBatchNo(log.getBatchNo());
                stockQueryVo.setSkuId(log.getSkuId());
                List<JdiStock> stocks = stockService.findJdiStock(stockQueryVo);
                odoVo.setOriginOrderNo(log.getBusinessCode());
                for (JdiStock stock : stocks) {
                    shipped = shipped.add(log.getHoldQuantity());
                    JdiStockChangeDto changeDto = makeStockChangeDto(odoVo, odoHeader.getOdoNo(), stock, BigDecimal.ZERO.subtract(log.getHoldQuantity()), detail.getOdoDetailNo());
                    if (hasConsumer) {
                        consumer.accept(changeDto);
                    }
                    // 扣减库存不抛异常为成功
                    logList.add(stockOperateService.executeDirectStockIO(changeDto));
                    priceChangeVoList.add(AgileConvert.convert(changeDto, JdiStockAveragePriceChangeVo.class));
                }
            }
            // 修改详情单状态
            JdiOdoDetail newDetail = AgileConvert.convert(detail, JdiOdoDetail.class);
            newDetail.setStatus(status);
            newDetail.setUpdatedId(vo.getOperatorId());
            newDetail.setUpdatedBy(vo.getOperatorName());
            newDetail.setUpdateDate(date);
            newDetail.setOrderNo(date.getTime());
            if (status == JdiOdoStatusEnum.FINISHED.getValue()) {
                newDetail.setShippedTime(date);
                newDetail.setShippedQuantity(shipped);
                totalShipped = totalShipped.add(shipped);
            }
            odoDetailService.updateStatus(newDetail);
        }
        // 修改单头状态
        JdiOdoHeader newOdoHeader = AgileConvert.convert(odoHeader, JdiOdoHeader.class);
        newOdoHeader.setOdoStatus(status);
        newOdoHeader.setUpdatedId(vo.getOperatorId());
        newOdoHeader.setUpdatedBy(vo.getOperatorName());
        newOdoHeader.setUpdateDate(date);
        newOdoHeader.setOrderNo(date.getTime());
        newOdoHeader.setShippedQuantity(totalShipped);
        odoHeaderService.updateStatus(newOdoHeader);
        return new HashMap<String, Object>() {
            {
                put("logList", logList);
                put("changed", priceChangeVoList);
                put("originOrderNo", odoHeader.getOriginOrderNo());
                put("timestamp", date.getTime());
                put("odoType", odoHeader.getOdoType());
            }
        };
    }
}

java8 实现集合分页

list.stream().skip(n * DEFAULT_MAX_BATCH_SIZE).limit(DEFAULT_MAX_BATCH_SIZE).parallel().collect(Collectors.toList())

java8 map收集两个键的情况，高频写法

customerMap.put(String.format("%s-%s", customerDto.getCustomerType().name(), customerDto.getCustomerName()), customerDto);