https://github.com/aNNiMON/Lightweight-Stream-API を使ってみた

SampleTest.java

package sample;

import java.util.ArrayList;
import java.util.List;
import java.util.NoSuchElementException;
import com.annimon.stream.Collectors;
import com.annimon.stream.Optional;
import com.annimon.stream.Stream;
import com.annimon.stream.function.Consumer;
import com.annimon.stream.function.Predicate;

import org.junit.Test;

import static org.junit.Assert.*;

public class SampleTest {

    @Test
    public void test1() {
        List<String> values = Stream
            .of(new String[] { "hoge", "fuga", "foobar" })
            .filter(
                new Predicate<String>() {
                    @Override
                    public boolean test(String value) {
                        return value.length() == 4;
                    }
                }
            )
            .sorted()
            .collect(Collectors.<String>toList());

        assertEquals(2, values.size());
        assertEquals("fuga", values.get(0));
        assertEquals("hoge", values.get(1));
    }

    @Test
    public void testOptional() {
        Optional<String> opt1 = Optional.of("hoge");
        assertTrue(opt1.isPresent());

        // orElseGet(Supplier)も使える
        assertEquals("hoge", opt1.orElse("fuga"));


        Optional<String> opt2 = Optional.ofNullable(null);
        assertFalse(opt2.isPresent());
        assertEquals("fuga", opt2.orElse("fuga"));
    }

    @Test(expected = NullPointerException.class)
    public void testOptional_of_null() {
        Optional.of(null);
    }

    @Test(expected = NoSuchElementException.class)
    public void testOptional_get() {
        Optional<String> opt = Optional.ofNullable(null);
        opt.get();
    }
}