Basic.java

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/* @test
 * @bug 8195649
 * @summary Basic functional test of Optional
 * @author Mike Duigou
 * @build ObscureException
 * @run testng Basic
 */

import java.util.List;
import java.util.NoSuchElementException;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicBoolean;

import static java.util.stream.Collectors.toList;

import static org.testng.Assert.*;
import org.testng.annotations.Test;

public class Basic {

    /**
     * Checks a block of assertions over an empty Optional.
     */
    void checkEmpty(Optional<String> empty) {
        assertTrue(empty.equals(Optional.empty()));
        assertTrue(Optional.empty().equals(empty));
        assertFalse(empty.equals(Optional.of("unexpected")));
        assertFalse(Optional.of("unexpected").equals(empty));
        assertFalse(empty.equals("unexpected"));

        assertFalse(empty.isPresent());
        assertTrue(empty.isEmpty());
        assertEquals(empty.hashCode(), 0);
        assertEquals(empty.orElse("x"), "x");
        assertEquals(empty.orElseGet(() -> "y"), "y");

        assertThrows(NoSuchElementException.class, () -> empty.get());
        assertThrows(NoSuchElementException.class, () -> empty.orElseThrow());
        assertThrows(ObscureException.class,       () -> empty.orElseThrow(ObscureException::new));

        var b = new AtomicBoolean();
        empty.ifPresent(s -> b.set(true));
        assertFalse(b.get());

        var b1 = new AtomicBoolean(false);
        var b2 = new AtomicBoolean(false);
        empty.ifPresentOrElse(s -> b1.set(true), () -> b2.set(true));
        assertFalse(b1.get());
        assertTrue(b2.get());

        assertEquals(empty.toString(), "Optional.empty");
    }

    /**
     * Checks a block of assertions over an Optional that is expected to
     * have a particular value present.
     */
    void checkPresent(Optional<String> opt, String expected) {
        assertFalse(opt.equals(Optional.empty()));
        assertFalse(Optional.empty().equals(opt));
        assertTrue(opt.equals(Optional.of(expected)));
        assertTrue(Optional.of(expected).equals(opt));
        assertFalse(opt.equals(Optional.of("unexpected")));
        assertFalse(Optional.of("unexpected").equals(opt));
        assertFalse(opt.equals("unexpected"));

        assertTrue(opt.isPresent());
        assertFalse(opt.isEmpty());
        assertEquals(opt.hashCode(), expected.hashCode());
        assertEquals(opt.orElse("unexpected"), expected);
        assertEquals(opt.orElseGet(() -> "unexpected"), expected);

        assertEquals(opt.get(), expected);
        assertEquals(opt.orElseThrow(), expected);
        assertEquals(opt.orElseThrow(ObscureException::new), expected);

        var b = new AtomicBoolean(false);
        opt.ifPresent(s -> b.set(true));
        assertTrue(b.get());

        var b1 = new AtomicBoolean(false);
        var b2 = new AtomicBoolean(false);
        opt.ifPresentOrElse(s -> b1.set(true), () -> b2.set(true));
        assertTrue(b1.get());
        assertFalse(b2.get());

        assertEquals(opt.toString(), "Optional[" + expected + "]");
    }

    @Test(groups = "unit")
    public void testEmpty() {
        checkEmpty(Optional.empty());
    }

    @Test(groups = "unit")
    public void testOfNull() {
        assertThrows(NullPointerException.class, () -> Optional.of(null));
    }

    @Test(groups = "unit")
    public void testOfPresent() {
        checkPresent(Optional.of("xyzzy"), "xyzzy");
    }

    @Test(groups = "unit")
    public void testOfNullableNull() {
        checkEmpty(Optional.ofNullable(null));
    }

    @Test(groups = "unit")
    public void testOfNullablePresent() {
        checkPresent(Optional.ofNullable("xyzzy"), "xyzzy");
    }

    @Test(groups = "unit")
    public void testFilterEmpty() {
        checkEmpty(Optional.<String>empty().filter(s -> { fail(); return true; }));
    }

    @Test(groups = "unit")
    public void testFilterFalse() {
        checkEmpty(Optional.of("xyzzy").filter(s -> s.equals("plugh")));
    }

    @Test(groups = "unit")
    public void testFilterTrue() {
        checkPresent(Optional.of("xyzzy").filter(s -> s.equals("xyzzy")), "xyzzy");
    }

    @Test(groups = "unit")
    public void testMapEmpty() {
        checkEmpty(Optional.empty().map(s -> { fail(); return ""; }));
    }

    @Test(groups = "unit")
    public void testMapPresent() {
        checkPresent(Optional.of("xyzzy").map(s -> s.replace("xyzzy", "plugh")), "plugh");
    }

    @Test(groups = "unit")
    public void testFlatMapEmpty() {
        checkEmpty(Optional.empty().flatMap(s -> { fail(); return Optional.of(""); }));
    }

    @Test(groups = "unit")
    public void testFlatMapPresentReturnEmpty() {
        checkEmpty(Optional.of("xyzzy")
                           .flatMap(s -> { assertEquals(s, "xyzzy"); return Optional.empty(); }));
    }

    @Test(groups = "unit")
    public void testFlatMapPresentReturnPresent() {
        checkPresent(Optional.of("xyzzy")
                             .flatMap(s -> { assertEquals(s, "xyzzy"); return Optional.of("plugh"); }),
                     "plugh");
    }

    @Test(groups = "unit")
    public void testOrEmptyEmpty() {
        checkEmpty(Optional.<String>empty().or(() -> Optional.empty()));
    }

    @Test(groups = "unit")
    public void testOrEmptyPresent() {
        checkPresent(Optional.<String>empty().or(() -> Optional.of("plugh")), "plugh");
    }

    @Test(groups = "unit")
    public void testOrPresentDontCare() {
        checkPresent(Optional.of("xyzzy").or(() -> { fail(); return Optional.of("plugh"); }), "xyzzy");
    }

    @Test(groups = "unit")
    public void testStreamEmpty() {
        assertEquals(Optional.empty().stream().collect(toList()), List.of());
    }

    @Test(groups = "unit")
    public void testStreamPresent() {
        assertEquals(Optional.of("xyzzy").stream().collect(toList()), List.of("xyzzy"));
    }
}