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anton0xf/Main.java

Created November 26, 2020 11:46
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мой пример к "кружку про ООП"
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Main.java
import java.io.IOException;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
class Main {
static class Loader<T> {
Client client;
Function<String, T> parser;
public Loader(Client client, Function<String, T> parser) {
this.client = client;
this.parser = parser;
}
public List<T> list(List<Long> ids) {
return ids.stream()
.map(this::get)
.collect(Collectors.toList());
}
public T get(Long id) {
String json = client.get(id);
return parser.apply(json);
}
}
static class BatchLoader<T> {
Client client;
Function<String, T> parser;
public BatchLoader(Client client, Function<String, T> parser) {
this.client = client;
this.parser = parser;
}
public List<T> list(List<Long> ids) {
Set<Long> set = new HashSet<Long>(ids);
return client.getAll().stream()
.map(line -> parser.apply(line))
.filter(set::contains)
.collect(Collectors.toList());
}
}
interface Parser {
long readLong(String input, String path);
String readString(String input, String path);
}
static class AJsonParser implements Parser {
ObjectMapper mapper;
@Override
public long readLong(String input, String path) {
JsonNode node = mapper.readValue(json, JsonNode.class);
return node.get(path).asLong();
}
@Override
public String readString(String input, String path) {
JsonNode node = mapper.readValue(json, JsonNode.class);
return node.get(path).asText();
}
}
static class CsvParser implements Parser {
}
static class TopicLoader {
TopicClient client = new TopicClient();
ObjectMapper mapper;
Loader<Topic> loader = new Loader<Topic>(client, this::parse);
public List<Topic> list(List<Long> ids) {
return loader.list(ids);
}
public Main.Topic parse(String json) {
try {
JsonNode node = mapper.readValue(json, JsonNode.class);
long id = node.get("id").asLong();
String title = node.get("title").asText();
return new Topic(id, title);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
static class UserLoader {
Parser parser;
TopicClient client = new TopicClient();
BatchLoader<User> loader = new BatchLoader<User>(client, this::parse);
public List<User> list(List<Long> ids) {
return loader.list(ids);
}
public Main.User parse(String line) {
long id = parser.readLong(line, "id");
String firstName = parser.readString(line, "fname");
String lastName = parser.readString(line, "lname");
return new User(id, firstName, lastName);
}
}
static class User {
long id;
String firstName;
String lastName;
public User(long id, String firstName, String lastName) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
}
}
static class Topic {
long id;
String title;
public Topic(long id, String title) {
this.id = id;
this.title = title;
}
}
interface Client {
String get(long id);
List<String> getAll();
}
static class UserClient implements Client {
public String get(long id) {
return "" + id;
}
@Override
public List<String> getAll() {
return List.of("....");
}
}
static class TopicClient implements Client {
public String get(long id) {
return "" + id;
}
}
}
@anton0xf
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https://checkvist.com/checklists/753734

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