test/jdk/java/lang/String/StringJoinTest.java

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/**
 * @test
 * @bug 5015163 8267529
 * @summary test String merge/join that is the inverse of String.split()
 * @run testng StringJoinTest
 * @author Jim Gish
 */
import java.util.ArrayList;
import java.util.List;
import java.util.StringJoiner;
import org.testng.annotations.Test;

import static org.testng.Assert.*;

@Test(groups = {"unit","string","lang","libs"})
public class StringJoinTest {
    private static final String DASH = "-";
    private static final String BEGIN = "Hi there";
    private static final String JIM = "Jim";
    private static final String JOHN = "John";
    private static final String AND_JOE = "and Joe";
    private static final String BILL = "Bill";
    private static final String BOB = "Bob";
    private static final String AND_BO = "and Bo";
    private static final String ZEKE = "Zeke";
    private static final String ZACK = "Zack";
    private static final String AND_ZOE = "and Zoe";

    /**
     * Tests the join() methods on String
     */
    public void testJoinStringVarargs() {
        // check a non-null join of String array (var-args) elements
        String expectedResult = BEGIN + DASH + JIM + DASH + JOHN + DASH + AND_JOE;
        String result = String.join(DASH, BEGIN, JIM, JOHN, AND_JOE);

        assertEquals(result, expectedResult, "BEGIN.join(DASH, JIM, JOHN, AND_JOE)");
        // test with just one element
        assertEquals(String.join(DASH, BEGIN), BEGIN);
    }

    public void testJoinStringArray() {
        // check a non-null join of Object[] with String elements
        String[] theBs = {BILL, BOB, AND_BO};
        String result = String.join(DASH, theBs);
        String expectedResult = BILL + DASH + BOB + DASH + AND_BO;
        assertEquals(result, expectedResult, "String.join(DASH, theBs)");
    }

    public void testJoinEmptyStringArray() {
        // check a non-null join of Object[] with String elements
        String[] empties = {};
        String result = String.join(DASH, empties);
        assertEquals(result, "", "String.join(DASH, empties)");
    }

    @Test(expectedExceptions = {NullPointerException.class})
    public void testJoinNullStringArray() {
        // check a non-null join of Object[] with String elements
        String[] empties = null;
        String result = String.join(DASH, empties);
    }

    @Test(expectedExceptions = {NullPointerException.class})
    public void testJoinNullIterableStringList() {
        // check join of an Iterables
        List<CharSequence> theZsList = null;
        String.join(DASH, theZsList);
    }

    public void testJoinIterableStringList() {
        // check join of an Iterables
        List<CharSequence> theZsList = new ArrayList<>();
        theZsList.add(ZEKE);
        theZsList.add(ZACK);
        theZsList.add(AND_ZOE);
        assertEquals(String.join(DASH, theZsList), ZEKE + DASH + ZACK + DASH
                + AND_ZOE, "String.join(DASH, theZsList))");
    }

    public void testJoinNullStringList() {
        List<CharSequence> nullList = null;
        try {
            assertEquals( String.join( DASH, nullList ), "null" );
            fail("Null container should cause NPE");
        } catch (NullPointerException npe) {}
        assertEquals(String.join(DASH, null, null), "null" + DASH + "null");
    }

    @Test(expectedExceptions = {NullPointerException.class})
    public void testJoinNullDelimiter() {
        String.join(null, JIM, JOHN);
    }

    public void testIgnoreDelimiterCoderJoin() {
        // 8267529: Ensure that joining zero or one latin-1 Strings with a UTF-16
        // delimiter produce a String with a latin-1 coder, since the delimiter
        // is not added.
        assertEquals("", new StringJoiner("\u2013").toString());
        assertEquals("foo", new StringJoiner("\u2013").add("foo").toString());
        assertEquals("", String.join("\u2013"));
        assertEquals("foo", String.join("\u2013", "foo"));
    }
}