java8对一些集合的优化操作

1.集合实体提取里面提起一个字段生成新的集合

 List shops = shopService.findList(searchParams);

 List ids = shops.stream().map(Shop::getShopId).collect(Collectors.toList());

2.给里面里面每个实体设置值

List list2 = list.getList();

list2.forEach(t -> t.setBannerId(1L));

3.集合的过滤生成新数组

List< Integer > transactionsIds = transactions.parallelStream().
 filter(t -> t.getType() == Transaction.GROCERY).
 sorted(comparing(Transaction::getValue).reversed()).
 map(Transaction::getId).
 collect(toList());
4.集合的排序
 List datas = daydatas.stream().sorted(Comparator.comparing(RiderForm::getRiderName))                 .collect(Collectors.toList());

public class RiderForm implements Serializable, Comparable {
　　 @Override     public int compareTo(             RiderForm o) {         return riderName.compareTo(o.getRiderName());     }
　　 @Override     public boolean equals(             final Object obj) {         if (obj == null) {             return false;         }         final RiderForm rf = (RiderForm) obj;         if (this == rf) {             return true;         } else {             return (this.riderName.equals(rf.riderName) && (this.orderType == rf.orderType));         }     }
 @Override     public int hashCode() {         int hashno = 7;         hashno = 13 * hashno + (riderName == null ? 0 : riderName.hashCode());         return hashno;     }

}
5.遍历map

map.entrySet().forEach(entry -> System.out.println("key:value = " + entry.getKey() + ":" + entry.getValue()));

转载于:https://www.cnblogs.com/loserchange/p/8317661.html