1.String/StringBuffer 改变为StringBuilder
2.
if(a.isEmpty()){ if(a.isEmpty() && b.isEmpty()){
if(b.isEmpty()){} -->
}
}
3.出现次数多的常量/字符串,采用定义的方式
4.if(list.size>0){} --> if(list.isEmpty()){}
5.重复常量的定义
private static final String OPERATION_TYPE = "operationType";