如何将对象list转为以某列为key，对象为value的map：

List<list> list = Lists.partition(this.trustContractList, Constant.ONE_THOUSAND);

for(Listli:list){

MapcontractMap = li.stream().collect(Collectors.toMap(TrustContractEx -> TrustContractEx.getProdContractNo(), TrustContractEx -> TrustContractEx));

}