test/jdk/java/util/Locale/AvailableLocalesTest.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * @test
 * @bug 4122700 8282319
 * @summary Verify implementation of getAvailableLocales() and availableLocales()
 * @run junit AvailableLocalesTest
 */

import java.util.Arrays;
import java.util.Locale;
import java.util.stream.Stream;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;
import org.junit.jupiter.params.provider.Arguments;

import static org.junit.jupiter.api.Assertions.assertNotEquals;

public class AvailableLocalesTest {

    /**
     * Test that Locale.getAvailableLocales() is non-empty and prints out
     * the returned locales - 4122700.
     */
    @Test
    public void nonEmptyLocalesTest() {
        Locale[] systemLocales = Locale.getAvailableLocales();
        assertNotEquals(systemLocales.length, 0, "Available locale list is empty!");
        System.out.println("Found " + systemLocales.length + " locales:");
        printLocales(systemLocales);
    }

    /**
     * Test to validate that the methods: Locale.getAvailableLocales()
     * and Locale.availableLocales() contain the same underlying elements
     */
    @Test
    public void streamEqualsArrayTest() {
        Locale[] arrayLocales = Locale.getAvailableLocales();
        Stream<Locale> streamedLocales = Locale.availableLocales();
        Locale[] convertedLocales = streamedLocales.toArray(Locale[]::new);
        if (Arrays.equals(arrayLocales, convertedLocales)) {
            System.out.println("$$$ Passed: The underlying elements" +
                    " of getAvailableLocales() and availableLocales() are the same!");
        } else {
            throw new RuntimeException("$$$ Error: The underlying elements" +
                    " of getAvailableLocales() and availableLocales()" +
                    " are not the same.");
        }
    }

    /**
     * Test to validate that the stream has the required
     * Locale.ROOT and Locale.US.
     */
    @ParameterizedTest
    @MethodSource("requiredLocaleProvider")
    public void requiredLocalesTest(Locale requiredLocale, String localeName) {
        if (Locale.availableLocales().anyMatch(loc -> (loc.equals(requiredLocale)))) {
            System.out.printf("$$$ Passed: Stream has %s!%n", localeName);
        } else {
            throw new RuntimeException(String.format("$$$ Error:" +
                    " Stream is missing %s!", localeName));
        }
    }

    // Helper method to print out all the system locales
    private void printLocales(Locale[] systemLocales) {
        Locale[] locales = new Locale[systemLocales.length];
        for (int i = 0; i < locales.length; i++) {
            Locale lowest = null;
            for (Locale systemLocale : systemLocales) {
                if (i > 0 && locales[i - 1].toString().compareTo(systemLocale.toString()) >= 0)
                    continue;
                if (lowest == null || systemLocale.toString().compareTo(lowest.toString()) < 0)
                    lowest = systemLocale;
            }
            locales[i] = lowest;
        }
        for (Locale locale : locales) {
            if (locale.getCountry().length() == 0)
                System.out.println("    " + locale.getDisplayLanguage() + ":");
            else {
                if (locale.getVariant().length() == 0)
                    System.out.println("        " + locale.getDisplayCountry());
                else
                    System.out.println("        " + locale.getDisplayCountry() + ", "
                            + locale.getDisplayVariant());
            }
        }
    }

    // Data provider for testStreamRequirements
    private static Stream<Arguments> requiredLocaleProvider() {
        return Stream.of(
                Arguments.of(Locale.ROOT, "Root locale"),
                Arguments.of(Locale.US, "US locale")
        );
    }
}