我有一个作者集合LinkedList<Author> autoren
,以及一系列书籍List<Book> buecher
。一本书与其作者之间的联系是作者的电子邮件地址。
Book 类有 Set
作者的电子邮件地址:private Set<String> autoren
.
对于每本书,我想获取相应的作者-作者并打印作者的姓氏和名字。
LinkedList<Author> autoren = (LinkedList<Autor>) dataController.getAutoren().stream()
.filter(s -> buch.getAutoren().contains(s.getEmailadresse()));
for (Author author: autoren) {
sysout(auther.getName())
}
我的 bool 数据模型看起来像
public class Buch {
private String title;
private String isbnNummer;
private Set<String> autoren;}
如何使用 lambda 表达式获取所有书籍的所有作者的列表,并按书籍名称进行筛选?
最佳答案
尚不完全清楚您想要什么,这里有一个可能有用的示例:
package ch.revault.java8;
import static java.lang.String.format;
import static java.util.Arrays.asList;
import static java.util.stream.Collectors.toMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.junit.Test;
public class AppTest {
@Test
public void testApp() {
List<Book> books = getBooks();
List<Author> authors = getAuthors();
String yourBookNameFilter = "The martian";
Map<String, Author> authorsByEmail = authors
.stream()
.collect(toMap(a -> a.email, a -> a));
books.stream()
.filter(b -> b.title.contains(yourBookNameFilter)) // <-- simple
// filter,
.flatMap(b -> b.authorEmails.stream())
.distinct()
.map(e -> authorsByEmail.get(e)) // you could inline
// authorsByEmail lookup
.forEach(a -> System.out.println(format("%s, %s", a.firstName, a.lastName)));
}
public class Author {
final String firstName;
final String lastName;
final String email;
public Author(String firstName, String lastName, String email) {
this.firstName = firstName;
this.lastName = lastName;
this.email = email;
}
}
public class Book {
final String title;
final String isbnNummer;
final Set<String> authorEmails;
public Book(String title, String isbnNummer, Set<String> authorEmails) {
this.title = title;
this.isbnNummer = isbnNummer;
this.authorEmails = authorEmails;
}
}
private List<Author> getAuthors() {
return asList(
new Author("f1", "l1", "e1@example.com"),
new Author("f2", "l2", "e2@example.com"),
new Author("f3", "l3", "e3@example.com"),
new Author("f4", "l4", "e4@example.com"));
}
private List<Book> getBooks() {
return asList(
new Book("The martian", "i1", new LinkedHashSet<>(asList("e2@example.com", "e4@example.com"))),
new Book("t2", "i2",
new LinkedHashSet<>(asList("e1@example.com", "e2@example.com", "e3@example.com"))));
}
}
关于java - 流式传输和过滤列表中包含的子列表中的数据,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40276680/