Java8中常用Lambda表达式

1、获取最大值、最小值

// 最大值
String codeOne = auditMessageDetailedEntity.stream().map(AuditMessageDetailedEntity::getCode).distinct() .max((e1, e2) -> e1.compareTo(e2)).get();
// 最小值
Date statementChargeBeginDates = settleOrders.stream().map(SettleOrder::getStatementChargeBeginDate).distinct().min((o1,o2)->o1.compareTo(o2)).get();

2、分组

// 多个分组属性，采用“_”连接
Map> groupByList = balanceDetailList.stream().collect(Collectors.groupingBy(t -> t.getSupplierCode()+"_"+t.getPaymentUnitCode()));

3、循环操作

confBankInfoVos = confBankInfos.stream().map(confBankInfo -> dozerBeanMapper.map(confBankInfo, ConfBankInfoDetailVo.class)).collect(Collectors.toList());

4、分页

onePageRecords = voList.stream().skip((pageNo-1)*pageSize).limit(pageSize).collect(Collectors.toList());

5、过滤

String ptCode =“abc”；
vo = voList.stream().filter(e -> e.getPayTermsCode().equals(ptCode)).collect(Collectors.toList()).get(0);

6、Map按照value排序

 public static Map sortMap2(Map map) {
	Map map = new HashMap<>();
	Map result = new ListOrderedMap();
	map.entrySet().stream().
	        sorted(Map.Entry.comparingByValue()).
	        forEachOrdered(entry -> result.put(entry.getKey(), entry.getValue()));
    return result；
}

7、计算某个Bigdecimal字段总和

orderMoney = orderList.stream().map(order -> order.getOrderAmount()).reduce(BigDecimal.ZERO, BigDecimal::add);