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package com.daonstar.web;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.stream.Collectors;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class ListToMapTest {
private List<Book> books;
private final String NAME = "책읽자";
private final int RELEASE_YEAR = 2009;
private final String ISBN = "0101234929";
private final int initAddBookCount = 3;
@Before
public void init() {
System.out.println("@Before");
books = new ArrayList<>();
booksAdds();
}
@After
public void tearDown() throws Exception {
System.out.println("@After");
books.clear();
}
private void booksAdds() {
for (int i = 0; i < initAddBookCount; i++) {
int releaseYear = RELEASE_YEAR;
if ( i > 1 ) {
releaseYear = RELEASE_YEAR + i;
}
books.add(new Book(NAME + i, releaseYear, ISBN + i));
}
}
private Map<String, String> listToMap(List<Book> books) {
return books.stream().collect(Collectors.toMap(Book::getIsbn, Book::getName));
}
@Test
public void whenConvertFromListToMap() {
System.out.println("@test1");
assertTrue(listToMap(books).size() ==3);
}
public Map<Integer, Book> listToMapWithDupKeyError(List<Book> books) {
return this.books.stream().collect(Collectors.toMap(Book::getReleaseYear, Function.identity()));
}
@Test(expected = IllegalStateException.class)
public void whenMapHasDuplicateKey_whthout_merge_function_then_runtime_exception() {
listToMapWithDupKeyError(books);
}
public Map<Integer, Book> listToMapWithDupKey(List<Book> books) {
return books.stream().collect(Collectors.toMap(Book::getReleaseYear, Function.identity(), (existing, replacement) -> existing));
}
@Test
public void whenMapHasDuplicateKeyThenMergeFunctionHandlesCollision() {
Map<Integer, Book> booksByYear = listToMapWithDupKey(books);
assertEquals(2, booksByYear.size());
assertEquals(ISBN + 0, booksByYear.get(RELEASE_YEAR).getIsbn());
}
public Map<Integer, Book> listToConcurrentMap(List<Book> books) {
return books.stream().collect(Collectors.toMap(Book::getReleaseYear, Function.identity(), (o1, o2) -> o1, ConcurrentHashMap::new));
}
@Test
public void whenCreateConcurrentHashMap() {
assertTrue(listToConcurrentMap(books) instanceof ConcurrentHashMap);
}
public TreeMap<String, Book> listToSortedMap(List<Book> books) {
return books.stream()
.sorted(Comparator.comparing(Book::getName))
.collect(Collectors.toMap(Book::getName, Function.identity(), (o1, o2) -> o1, TreeMap::new));
}
@Test
public void whenMapisSorted() {
String firstBookName = "책읽자0";
assertTrue(listToSortedMap(books).firstEntry().getKey().equals(firstBookName));
}
}
나름 TDD하면서 해봤다.
아직 JUnit도 어설퍼서 이것저것 태스트 하느라 로그도 찍었다.
Collectors.toMap 요놈 이용해서 리스트를 맵으로 바꾸면 되는 요지인데, 키 중복일때 처리 방법도 있다.
요지는 list to map 인데 테스트 관련해서 리팩토링 할려고 노력중이라 코드가 산으로 가고 다른 생각이 많이 든다.
참고 https://www.baeldung.com/java-collectors-tomap
Java 8 Collectors toMap | Baeldung
Learn how to use the toMap() method of the Collectors class.
www.baeldung.com
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