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https://github.com/benelog/lambda-resort
examples of filtering, sorting, mapping by Java, Groovy, Scala, Kotlin, Xtend, Ceylon
https://github.com/benelog/lambda-resort
groovy java lambda xtend
Last synced: 4 days ago
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examples of filtering, sorting, mapping by Java, Groovy, Scala, Kotlin, Xtend, Ceylon
- Host: GitHub
- URL: https://github.com/benelog/lambda-resort
- Owner: benelog
- Created: 2015-01-05T00:31:09.000Z (almost 10 years ago)
- Default Branch: master
- Last Pushed: 2016-01-03T20:00:03.000Z (about 9 years ago)
- Last Synced: 2024-04-16T11:04:28.093Z (9 months ago)
- Topics: groovy, java, lambda, xtend
- Language: Java
- Size: 411 KB
- Stars: 25
- Watchers: 7
- Forks: 10
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Filtering, sorting, mapping
### Backgrounds
[Guest.java](src/main/java/com/naver/helloworld/resort/domain/Guest.java)
```java
public class Guest {
private final int grade;
private final String name;
private final String company;
...
}
```
[GuestRepository.java](src/main/java/com/naver/helloworld/resort/repository/GuestRepository.java)
```java
import java.util.List;
public interface GuestRepository {
public List findAllGuest ();
}
```
[ResortService.java](src/main/java/com/naver/helloworld/resort/service/ResortService.java)
```java
public interface ResortService {
public List findGuestNamesByCompany (String company);
}
```
## Implementations by classic Java
### JDK Collections framework
[ClassicJavaResort.java](src/main/java/com/naver/helloworld/resort/service/ClassicJavaResort.java)
```java
public List findGuestNamesbyCompany(String company) {
List all = repository.findAllGuest();
List filtered = filter(guests, company);
sort(filtered);
return mapNames(filtered);
}
private List filter(List guests, String company) {
List filtered = new ArrayList<>();
for(Guest guest : guests ) {
if (company.equals(guest.getCompany())) {
filtered.add(guest);
}
}
return filtered;
}
private void sort(List guests) {
Collections.sort(guests, new Comparator() {
public int compare(Guest o1, Guest o2) {
return Integer.compare(o1.getGrade(), o2.getGrade());
}
});
}
private List mapNames(List guests) {
List names = new ArrayList<>();
for(Guest guest : guests ) {
names.add(guest.getName());
}
return names;
}
```
### [Guava](https://github.com/google/guava)
[GuavaResort.java](src/main/java/com/naver/helloworld/resort/service/GuavaResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAll();
List sorted = FluentIterable.from(all)
.filter(new Predicate() {
public boolean apply(Guest g) {
return company.equals(g.getCompany());
}
})
.toSortedList(Ordering.natural().onResultOf(
new Function() {
public Integer apply(Guest g) {
return g.getGrade();
}
}));
return FluentIterable.from(sorted)
.transform(new Function() {
public String apply(Guest g) {
return g.getName();
}
})
.toList();
}
```
### [Totally Lazy](http://totallylazy.com/)
[TotallyLazyResort.java](src/main/java/com/naver/helloworld/resort/service/TotallyLazyResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAll();
return Sequences.sequence(all)
.filter(new Predicate() {
public boolean matches(Guest g) {
return company.equals(g.getCompany());
}
})
.sortBy(new Callable1(){
public Integer call(Guest g) {
return g.getGrade();
}
})
.map(new Callable1(){
public String call(Guest g) {
return g.getName();
}
})
.toList();
}
```
### [GS Collections](https://github.com/goldmansachs/gs-collections)
[GsCollectoinsResort.java](src/main/java/com/naver/helloworld/resort/service/GsCollectionsResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAll();
return FastList.newList(all)
.select(new Predicate() {
public boolean accept(Guest g) {
return company.equals(g.getCompany());
}
})
.sortThisBy(new Function() {
public Integer valueOf(Guest g) {
return g.getGrade();
}
})
.collect(new Function () {
public String valueOf(Guest g) {
return g.getName();
}
});
}
```
### [Bolts](https://bitbucket.org/stepancheg/bolts/wiki/Home)
[BoltsResort.java](src/main/java/com/naver/helloworld/resort/service/BoltsResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAllGuest();
return Cf.list(all)
.filter(new Function1B() {
public boolean apply(Guest g) {
return company.equals(g.getCompany());
}
})
.sortBy(new Function() {
public Integer apply(Guest g) {
return g.getGrade();
}
})
.map(new Function() {
public String apply(Guest g) {
return g.getName();
}
});
}
```
### [Op4j](www.op4j.org)
[Op4JResort.java](src/main/java/com/naver/helloworld/resort/service/Op4JResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAllGuest();
return Op.on(all)
.removeAllFalse(new IFunction() {
public Boolean execute(Guest g, ExecCtx ctx) throws Exception {
return company.equals(g.getCompany());
}
})
.sortBy(new IFunction() {
public Integer execute(Guest g, ExecCtx ctx) throws Exception {
return g.getGrade();
}
})
.map(new IFunction() {
public String execute(Guest g, ExecCtx ctx) throws Exception {
return g.getName();
}
}).get();
}
```
### [Lambdaj](https://code.google.com/p/lambdaj)
[LambdaJResort.java](src/main/java/com/naver/helloworld/resort/service/LambdaJResort.java)
```java
import static ch.lambdaj.Lambda.*;
import static org.hamcrest.Matchers.*;
...
public List findGuestNamesByCompany(final String company) {
List all = repository.findAll();
return LambdaCollections.with(all)
.retain(having(on(Guest.class).getCompany(), equalTo(company)))
.sort(on(Guest.class).getGrade())
.extract(on(Guest.class).getName());
}
```
### [Functional Java](http://functionaljava.org/)
[FunctionalJavaResort.java](src/main/java/com/naver/helloworld/resort/service/FunctionalJavaResort.java)
```java
public List findGuestNamesByCompany(String company) {
List all = repository.findAll();
Collection mapped = Stream.iterableStream(all)
.filter(new F() {
public Boolean f(Guest g){
return company.equals(g.getCompany());
}
})
.sort(Ord.ord(
new F>() {
public F f(final Guest a1) {
return new F() {
public Ordering f(final Guest a2) {
int x = Integer.compare(a1.getGrade(), a2.getGrade());
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
}
};
}
}))
.map(new F() {
public String f(Guest g) {
return g.getName();
}
})
.toCollection();
return new ArrayList(mapped);
}
```
### [Apache Commons Collections](http://commons.apache.org/proper/commons-collections/)
[CommonsCollectionsResort.java](src/main/java/com/naver/helloworld/resort/service/CommonsCollectionsResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAll();
List filtered = ListUtils.select(all, new Predicate() {
public boolean evaluate(Guest g) {
return company.equals(g.getCompany());
}
});
Collections.sort(filtered, new Comparator() {
public int compare(Guest o1, Guest o2) {
return Integer.compare(o1.getGrade(), o2.getGrade());
}
});
Collection names = CollectionUtils.collect(filtered, new Transformer(){
public String transform(Guest g) {
return g.getName();
}
});
return new ArrayList<>(names);
}
```
### [Jedi](http://jedi.codehaus.org/)
[JediResort.java](src/main/java/com/naver/helloworld/resort/service/JediResort.java)
```java
public List findGuestNamesByCompany(final String company) {
List all = repository.findAll();
List filtered = FunctionalPrimitives.select(all, new Filter() {
public Boolean execute(Guest g) {
return company.equals(g.getCompany());
}
});
List sorted = Comparables.sort(filtered, new Functor() {
public Integer execute(Guest g) {
return g.getGrade();
}
});
return FunctionalPrimitives.map(sorted, new Functor() {
public String execute(Guest g) {
return g.getName();
}
});
}
```
## Implementations by other JVM languages
- Groovy : 2.3.9
- Scala : 2.11.4
- Kotlin : 0.10.195
- Xtend : 2.7
- Ceylon : 1.1.0
### [Groovy](http://groovy.codehaus.org/)
[GroovyAdvancedResort.groovy](src/main/groovy/com/naver/helloworld/resort/service/GroovyAdvancedResort.groovy)
```groovy
List findGuestNamesByCompany(String company) {
List all = repository.findAll()
all.findAll { it.company == company }
.sort { it.grade }
.collect { it.name }
}
```
### [Scala](http://www.scala-lang.org/)
[ScalaAdvancedResort.scala](src/main/scala/com/naver/helloworld/resort/service/ScalaAdvancedResort.scala)
```scala
import scala.collection.JavaConversions._
...
def findGuestNamesByCompany(company: String): java.util.List[String] = {
val all = repository.findAll
all.filter ( _.getCompany == company)
.sortBy ( _.getGrade )
.map ( _.getName )
}
```
### [Kotlin](http://kotlinlang.org)
[KotlinAdvancedResort.kt](src/main/kotlin/com/naver/helloworld/resort/service/KotlinAdvancedResort.kt)
```kotlin
override fun findGuestNamesByCompany(company: String): List {
val all = repository.findAll()
return all.filter { it.getCompany() == company }
.sortBy { it.getGrade() }
.map { it.getName() }
}
```
### [Xtend](http://www.eclipse.org/xtend/)
[XtendAdvancedResort.xtend](src/main/xtend/com/naver/helloworld/resort/service/XtendAdvancedResort.xtend)
```xtend
override findGuestNamesByCompany(String aCompany) {
val all = repository.findAll()
all.filter [company == aCompany]
.sortBy[grade]
.map[name]
}
```
### [Ceylon](http://ceylon-lang.org/)
[resort.ceylon](src/main/ceylon/com/naver/helloworld/resort/service/resort.ceylon)
```ceylon
import ceylon.interop.java { CeylonIterable }
import java.util {JList = List, JArrayList = ArrayList }
import java.lang {JString = String}
...
shared actual JList findGuestNamesByCompany(String company) {
value all = repository.findAll() ;
value names = CeylonIterable(all)
.filter((Guest g) => g.company == company)
.sort(byIncreasing((Guest g) => g.grade.intValue()))
.map((Guest g) => g.name);
value jnames = JArrayList();
for (name in names) {jnames.add(JString(name));}
return jnames;
}
```
## Implementations by modern Java
[ModernJavaAdvancedResort.java](src/main/java/com/naver/helloworld/resort/service/ModernJavaAdvancedResort.java)
```java
public List findGuestNamesByCompany(String company) {
List guests = repository.findAll();
return guests.stream()
.filter(g -> company.equals(g.getCompany()))
.sorted(Comparator.comparing(Guest::getGrade))
.map(Guest::getName)
.collect(Collectors.toList());
}
```
# Refactoring by lambda expressions
## Async Servlet
### Classic Java
[ClassicAsyncServlet.java](src/main/java/com/naver/helloworld/web/ClassicAsyncServlet.java)
```java
public void doGet(final HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
final AsyncContext asyncContext = request.startAsync();
asyncContext.start(new Runnable() {
public void run() {
// long running job
asyncContext.dispatch("/status.jsp");
}
});
}
```
### Modern Java
[ModernAsyncServlet.java](src/main/java/com/naver/helloworld/web/ModernAsyncServlet.java)
```java
public void doGet(final HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
AsyncContext asyncContext = request.startAsync();
asyncContext.start(() -> {
// long running job
asyncContext.dispatch("/status.jsp");
});
}
```
## Spring JDBC
### Classic Java
[ClassicJdbcRepository.java](src/main/java/com/naver/helloworld/resort/repository/ClassicJdbcRepository.java)
```java
public List findAll() {
return jdbcTemplate.query(SELECT_ALL, new RowMapper(){
public Guest mapRow(ResultSet rs, int rowNum) throws SQLException {
return new Guest (
rs.getInt("id"),
rs.getString("name"),
rs.getString("company"),
rs.getInt("grade")
);
}
});
}
```
### Modern Java
[ModernJdbcRepository.java](src/main/java/com/naver/helloworld/resort/repository/ModernJdbcRepository.java)
```java
public List findAll() {
return jdbcTemplate.query(SELECT_ALL,
(rs, rowNum) ->new Guest (
rs.getInt("id"),
rs.getString("name"),
rs.getString("company"),
rs.getInt("grade")
)
);
}
```
### Event bindings in Android
### Classic Java
[ClassicFragment.java](src/main/java/com/naver/helloworld/resort/android/ClassicFragment.java)
```java
Button calcButton = (Button) view.findViewById(R.id.calcBtn);
Button sendButton = (Button) view.findViewById(R.id.sendBtn);
calcButton.setOnClickListener(new OnClickListener() {
public void onClick(View view) {
calculate();
}
});
sendButton.setOnClickListener(new OnClickListener() {
public void onClick(View view) {
send();
}
});
```
### Modern Java
[ModernFragment.java](src/main/java/com/naver/helloworld/web/ModernAsyncServlet.java)
```java
Button calcButton = (Button) view.findViewById(R.id.calcBtn);
Button sendButton = (Button) view.findViewById(R.id.sendBtn);
calcButton.setOnClickListener(v -> calculate());
sendButton.setOnClickListener(v -> send());
```
# Frameworks using lambda expressions
### [Lambda Behave](http://richardwarburton.github.io/lambda-behave/)
[ResortServiceSpec.java](src/test/java/com/naver/helloworld/resort/service/ResortServiceSpec.java)
```java
@RunWith(JunitSuiteRunner.class)
public class ResortServiceSpec {{
GuestRepository repository = new MemoryRepository();
ResortService service = new ModernJavaResort(repository);
describe("ResortService with modern Java", it -> {
it.isSetupWith(() -> {
repository.save(
new Guest(1, "jsh", "Naver", 15),
new Guest(2, "hny", "Line", 10),
new Guest(3, "chy", "Naver", 5)
);
});
it.isConcludedWith(repository::deleteAll);
it.should("find names of guests by company ", expect -> {
List names = service.findGuestNamesByCompany("Naver");
expect.that(names).isEqualTo(Arrays.asList("chy","jsh"));
});
});
}}
```
### [Jinq](http://www.jinq.org/)
[JinqResort.java](src/main/java/com/naver/helloworld/resort/service/JinqResort.java)
```java
private EntityManager em;
@Autowired
public JinqResort(EntityManager em) {
this.em = em;
}
private JinqStream stream(Class clazz) {
return new JinqJPAStreamProvider(em.getEntityManagerFactory()).streamAll(em, clazz);
}
public List findGuestNamesByCompany(String company) {
return stream(Guest.class)
.where(g -> g.getCompany().equals(company))
.sortedBy(Guest::getGrade)
.select(Guest::getName)
.toList();
}
```
A query generated by JinqResort
```sql
Hibernate: select guest0_.id as id1_0_, guest0_.company as company2_0_, guest0_.grade as grade3_0_, guest0_.name as name4_0_ from guest guest0_ where guest0_.company=? order by guest0_.grade ASC limit ?
```
### [Spark](http://www.sparkjava.com/)
[SparkServer.java](src/main/java/com/naver/helloworld/web/SparkServer.java)
```java
import static spark.Spark.*;
import com.naver.helloworld.resort.service.ResortService;
public class SparkServer {
public static void main(String[] args) {
get("/guests/:company", (request, response) -> {
String company = request.params(":company");
return "No guests from " + company;
});
}
}
```
[ResortServer.java](src/main/java/com/naver/helloworld/resort/ResortServer.java) (Spark + Spring)
```java
@SpringBootApplication
public class ResortServer {
@Autowired
private ResortService service;
public void start() {
get("/guests/:company", (request, response) -> {
String company = request.params(":company");
List names = service.findGuestNamesByCompany(company);
return "Guests from " + company + " : " + names;
});
}
public static void main(String[] args) {
ApplicationContext context = SpringApplication.run(ResortServer.class);
context.getBean(ResortServer.class).start();
}
}
```