Java-筛选器返回空值

Question

我正在尝试筛选列表，但每次搜索都返回空值。我想尽一切办法，但什么也没发生。请帮我打这个

public class IssuerCreditDetailsUpdate implements ItemProcessor<Isin_Master, Issuer_credit_rating_details> {
protected final Logger logger = Logger.getLogger(this.getClass().getName());
static ArrayList<Credit_rating_details> Credit = new ArrayList<Credit_rating_details>();
private String validCreditRating = null;
@Override
public Issuer_credit_rating_details process(Isin_Master item) throws Exception {
Issuer_credit_rating_details row = new Issuer_credit_rating_details();
if(isCreditRatingValid(item.getIssuer_Id())!= null) {   
row.setIssuer_id(item.getIssuer_Id());
row.setName_of_issuer(item.getIssuerName());
return row;
}
return null;
}
private String isCreditRatingValid(String issuerid) {
System.out.println(Credit.stream().filter(i-> i.getIssuer_id().contains(issuerid)).collect(Collectors.toList()));
List<Credit_rating_details> result = Credit.stream().filter(i-> i.getIssuer_id().contains(issuerid)).collect(Collectors.toList());
if(!result.isEmpty() ) {
validCreditRating = result.get(0).getCredit_rating();
return result.get(0).getCredit_rating();
}else {
return null;
}
}
}

Answer 1

i-> i.getIssuer_id().contains(issuerid)可能与您预期的不匹配。Credit_rating_details.getIssuer_id((返回的类型是什么？它也是字符串吗？输入issuerid和Credit_rating_details issuer_id是否可能在不同的情况下
尝试i-> i.getIssuer_id().equalsIgnoreCase(issuerid)，看看是否会得到不同的结果。