我有两个列表。我从数据库创建一个，从Csv文件创建一个。现在我想收集包含数据库和csv文件的列表中的记录。我写了如下代码
BiPredicate<Trainee, Trainee> sameTrainee = (dbTrainee, csvTrainee) -> {
String dbTraineeFirstName = dbTrainee.getFirstName();
String dbTraineeLastName = dbTrainee.getLastName();
String dbTraineeEmail = dbTrainee.getEmail();
LocalDateTime dbTraineeCompletionDate = dbTrainee.getSessionDateTime();
String text = dbTraineeCompletionDate.format(DATE_TIME_FORMATTER);
LocalDateTime dbTraineeSessionDateTime = LocalDateTime.parse(text);
String dbTraineePhoneNumber = dbTrainee.getPhoneNumber();
String dbTraineeSsn = dbTrainee.getSocialSecurityLastFour();
String dbTraineeStreetOne = dbTrainee.getStreetOne();
String dbTraineeCity = dbTrainee.getCity();
String csvTraineeFirstName = csvTrainee.getFirstName();
String csvTraineeLastName = csvTrainee.getLastName();
String csvTraineeEmail = csvTrainee.getEmail();
LocalDateTime csvTraineeSessionDateTime = csvTrainee.getSessionDateTime();
String csvTraineePhoneNumber = csvTrainee.getPhoneNumber();
String csvTraineeSsn = csvTrainee.getSocialSecurityLastFour();
String csvTraineeStreetOne = csvTrainee.getStreetOne();
String csvTraineeCity = csvTrainee.getCity();
int dbTraineeSsnLength = dbTraineeSsn.length();
int csvTraineeSsnLength = csvTraineeSsn.length();
if (dbTraineeSsnLength != csvTraineeSsnLength) {
if (dbTraineeSsnLength == 4 && dbTraineeSsn.startsWith("0")) {
String dbTraineeSsnLast3Digits = dbTraineeSsn.substring(dbTraineeSsn.length() - 3);
if (csvTraineeSsnLength == 3 && csvTraineeSsn.endsWith(dbTraineeSsnLast3Digits)) {
csvTraineeSsn = "0" + csvTraineeSsn;
}
}
}
return dbTraineeFirstName.equals(csvTraineeFirstName)
&& dbTraineeLastName.equals(csvTraineeLastName)
&& dbTraineeEmail.equals(csvTraineeEmail)
&& dbTraineeSessionDateTime.equals(csvTraineeSessionDateTime)
&& dbTraineePhoneNumber.equals(csvTraineePhoneNumber)
&& dbTraineeSsn.equals(csvTraineeSsn)
&& dbTraineeStreetOne.equals(csvTraineeStreetOne)
&& dbTraineeCity.equals(csvTraineeCity);
};
并称之为
List<Trainee> foundInBothList = dbMonthlyTraineeList.stream()
.filter(dbTrainee -> csvTraineeList.stream()
.anyMatch(csvTrainee -> {
return sameTrainee.test(dbTrainee, csvTrainee);
})
).collect(Collectors.toList());
List<Trainee> notInFileList = dbMonthlyTraineeList.stream()
.filter(dbTrainee -> csvTraineeList.stream()
.noneMatch(csvTrainee -> {
return sameTrainee.test(dbTrainee, csvTrainee);
})
).collect(Collectors.toList());
工作正常。但是，因为我的BiPredicate变得越来越不整洁。所以我创建了一个类并收集了如下所示的集合中的所有谓词
public class PlcbMonthlyReportStatisticsBiPredicates {
public static BiPredicate<Trainee, Trainee> isValidFirstName() {
return (dbTrainee, csvTrainee) -> {
String dbTraineeFirstName = dbTrainee.getFirstName();
String csvTraineeFirstName = csvTrainee.getFirstName();
return dbTraineeFirstName.equals(csvTraineeFirstName);
};
}
public static BiPredicate<Trainee, Trainee> isValidSsn() {
return (dbTrainee, csvTrainee) -> {
String dbTraineeSsn = dbTrainee.getSocialSecurityLastFour();
String csvTraineeSsn = csvTrainee.getSocialSecurityLastFour();
...
return dbTraineeSsn.equals(csvTraineeSsn);
};
}
....
public static List<BiPredicate<Trainee, Trainee>> getAllBiPredicates() {
List<BiPredicate<Trainee, Trainee>> allPredicates = Arrays.asList(
isValidFirstName(),
isValidSsn(),
...
);
return allPredicates;
}
}
现在我收集所有谓词但是如何在我的anyMatch（）和noneMatch（）中应用这些谓词。我试过这个但是cources得到错误
List<Trainee> foundInBothList1 = dbMonthlyTraineeList.stream()
.filter(dbTrainee -> csvTraineeList.stream()
.anyMatch(csvTrainee -> {
List<BiPredicate<Trainee, Trainee>> allBiPredicates = getAllBiPredicates();
return allBiPredicates.stream().reduce(BiPredicate::and).orElse((x,y)->true); //error
})
).collect(Collectors.toList());
我该如何应用呢？我的做法是对的吗？
**修改
@Entity
public class Trainee {
private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss");
private LocalDateTime sessionDateTime;
private String firstName;
....
@Override
public boolean equals(Object otherObject) {
// Are the same?
if (this == otherObject) {
return true;
}
// Is otherObject a null reference?
if (otherObject == null) {
return false;
}
// Do they belong to the same class?
if (this.getClass() != otherObject.getClass()) {
return false;
}
// Get the reference of otherObject in a otherTrainee variable
Trainee otherTrainee = (Trainee)otherObject;
LocalDateTime dbTraineeCompletionDate = this.getSessionDateTime();
String text = dbTraineeCompletionDate.format(DATE_TIME_FORMATTER);
LocalDateTime dbTraineeSessionDateTime = LocalDateTime.parse(text);
String dbTraineeSsn = this.socialSecurityLastFour;
String csvTraineeSsn = otherTrainee.getSocialSecurityLastFour();
int dbTraineeSsnLength = dbTraineeSsn.length();
int csvTraineeSsnLength = csvTraineeSsn.length();
if (dbTraineeSsnLength != csvTraineeSsnLength) {
if (dbTraineeSsnLength == 4 && dbTraineeSsn.startsWith("0")) {
String dbTraineeSsnLast3Digits = dbTraineeSsn.substring(dbTraineeSsn.length() - 3);
if (csvTraineeSsnLength == 3 && csvTraineeSsn.endsWith(dbTraineeSsnLast3Digits)) {
csvTraineeSsn = "0" + csvTraineeSsn;
}
}
}
boolean isEqual = (this.firstName.equals(otherTrainee.firstName)
&& this.lastName.equals(otherTrainee.lastName)
&& this.email.equals(otherTrainee.email)
&& dbTraineeSessionDateTime.equals(otherTrainee.sessionDateTime)
&& this.phoneNumber.equals(otherTrainee.phoneNumber)
&& dbTraineeSsn.equals(csvTraineeSsn)
&& this.streetOne.equals(otherTrainee.streetOne)
&& this.city.equals(otherTrainee.city)
);
return isEqual;
}
@Override
public int hashCode() {
int hash = 37;
int code = 0;
code = (firstName == null ? 0 : firstName.hashCode());
hash = hash * 59 + code;
code = (lastName == null ? 0 : lastName.hashCode());
hash = hash * 59 + code;
code = (email == null ? 0 : email.hashCode());
hash = hash * 59 + code;
code = (sessionDateTime == null ? 0 : sessionDateTime.hashCode());
hash = hash * 59 + code;
code = (phoneNumber == null ? 0 : phoneNumber.hashCode());
hash = hash * 59 + code;
code = (socialSecurityLastFour == null ? 0 : socialSecurityLastFour.hashCode());
hash = hash * 59 + code;
code = (streetOne == null ? 0 : streetOne.hashCode());
hash = hash * 59 + code;
code = (city == null ? 0 : city.hashCode());
hash = hash * 59 + code;
return hash;
}
}
编辑2（在覆盖hascode（）和equals（）之后） ------------------------------------------------- < /强>
在两者中找到：
List<Trainee> foundInBothList1 = dbMonthlyTraineeList.stream()
.filter(dbTrainee -> csvTraineeList.stream()
.anyMatch(csvTrainee -> {
return allBiPredicates.stream().reduce(BiPredicate::and).orElse((x,y)->true).test(dbTrainee, csvTrainee);
})
).collect(Collectors.toList());
List<Trainee> foundInBothList = new ArrayList<>(dbMonthlyTraineeList);
//foundInBothList.retainAll(new HashSet<>(csvTraineeList));
foundInBothList.retainAll(csvTraineeList);
在数据库中找到但不是在CSV
中找到List<Trainee> notInCsvFileList1 = dbMonthlyTraineeList.stream()
.filter(dbTrainee -> csvTraineeList.stream()
.noneMatch(csvTrainee -> {
return allBiPredicates.stream().reduce(BiPredicate::and).orElse((x,y)->true).test(dbTrainee, csvTrainee);
})
).collect(Collectors.toList());
//find out that elements of dbMonthlyTraineeList which is not present in arraylist(csvTraineeList).
List<Trainee> notInCsvFileList = new ArrayList<>(dbMonthlyTraineeList);
notInCsvFileList.removeAll(csvTraineeList);
答案 0 :(得分：2)
看起来你在想这个。为什么不用您的equals双谓词代码覆盖sameTrainee？ （别忘了也覆盖hashCode。）
执行此操作后，您可以使用以下命令保留两个列表中的Trainee：
Set<Trainee> foundInBothList = new HashSet<>(dbMonthlyTraineeList);
foundInBothList.retainAll(new HashSet<>(csvTraineeList));
这个解决方案是O（n），所以它的性能比你的解决方案好很多，即O（n²）。这是因为contains操作是Set上的常量时间。
但是如果你真的想要编译你的代码，你只需要在有错误的地方调用test方法：
return allBiPredicates.stream().reduce(BiPredicate::and)
.orElse((x,y)->true)
.test(dbTrainee, csvTrainee);