Java疑难杂症

Arrays.asList() 操作集合问题

List<String> arrayList = Arrays.asList("1", "@", "3");
System.out.println(arrayList);
arrayList.remove("1");

--- 控制台输出 ---
[1, @, 3]
Exception in thread "main" java.lang.UnsupportedOperationException
    at java.util.AbstractList.remove(AbstractList.java:161)
    at java.util.AbstractList$Itr.remove(AbstractList.java:374)
    at java.util.AbstractCollection.remove(AbstractCollection.java:293)
    at com.dindo.bill.service.impl.BusinessBillPayeeServiceImpl.main(BusinessBillPayeeServiceImpl.java:1564)

查看源码可以发现，此ArrayList不是彼ArrayList，Arrays类中声明了一个静态类，而它的类名就叫ArrayList，并不是继承AbstractList的ArrayList。
  private static class ArrayList<E> extends AbstractList<E>
  implements RandomAccess, java.io.Serializable{

  }

public class ArrayList<E> extends AbstractList<E>
        implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
}
解决方法：
new ArrayList(Arrays.asList("1", "@", "3")); 即可操作集合。

alibaba.fastjson 与实体转换

JSONObject jsonObject = JSONObject.parseObject(josn);
/** 这里直接强转实体或抛出转换异常 因此先转Map再转实体 */
Map billPayeeEntity = (Map) jsonObject.get("billPayeeEntity");
BillPayeeEntity user=JSON.parseObject(JSON.toJSONString(billPayeeEntity),BillPayeeEntity.class);
/** 集合先转JSONArray */
JSONArray jsonArray = jsonObject.getJSONArray("billPayeeRecordEntities");
        List<BillPayeeRecordEntity> billPayeeRecordEntities = jsonArray.toJavaList(BillPayeeRecordEntity.class);

拆分问题

在java中函数split(“.”)必须是是split("\\.").