jdk/test/java/util/StringJoiner/MergeTest.java

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 * 2 along with this work; if not, write to the Free Software Foundation,
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/**
 * @test
 * @bug 8017231 8020977
 * @summary test  StringJoiner::merge
 * @run testng MergeTest
 */

import java.util.StringJoiner;
import java.util.stream.Stream;
import org.testng.annotations.Test;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.fail;

@Test
public class MergeTest {
    public void testNull() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        try {
            sj.merge(null);
            fail("Should throw NullPointerException!");
        } catch (NullPointerException npe) {
            // expected
        }
    }

    public void testSimple() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        StringJoiner other = new StringJoiner(",", "[", "]");
        Stream.of("a", "b", "c").forEachOrdered(sj::add);
        Stream.of("d", "e", "f").forEachOrdered(other::add);

        sj.merge(other);
        assertEquals(sj.toString(), "{a,b,c,d,e,f}");
    }

    public void testEmptyOther() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        StringJoiner other = new StringJoiner(",", "[", "]");
        Stream.of("a", "b", "c").forEachOrdered(sj::add);

        sj.merge(other);
        assertEquals(sj.toString(), "{a,b,c}");

        other.setEmptyValue("EMPTY");
        sj.merge(other);
        assertEquals(sj.toString(), "{a,b,c}");
    }

    public void testEmptyThis() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        StringJoiner other = new StringJoiner(":", "[", "]");
        Stream.of("d", "e", "f").forEachOrdered(other::add);

        sj.merge(other);
        assertEquals(sj.toString(), "{d:e:f}");

        sj = new StringJoiner(",", "{", "}").setEmptyValue("EMPTY");
        assertEquals(sj.toString(), "EMPTY");
        sj.merge(other);
        assertEquals(sj.toString(), "{d:e:f}");
    }

    public void testEmptyBoth() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        StringJoiner other = new StringJoiner(":", "[", "]");

        sj.merge(other);
        assertEquals(sj.toString(), "{}");

        other.setEmptyValue("NOTHING");
        sj.merge(other);
        assertEquals(sj.toString(), "{}");

        sj = new StringJoiner(",", "{", "}").setEmptyValue("EMPTY");
        assertEquals(sj.toString(), "EMPTY");
        sj.merge(other);
        assertEquals(sj.toString(), "EMPTY");
    }

    public void testCascadeEmpty() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        StringJoiner o1 = new StringJoiner(":", "[", "]").setEmptyValue("Empty1");
        StringJoiner o2 = new StringJoiner(",", "<", ">").setEmptyValue("Empty2");

        o1.merge(o2);
        assertEquals(o1.toString(), "Empty1");

        sj.merge(o1);
        assertEquals(sj.toString(), "{}");
    }

    public void testDelimiter() {
        StringJoiner sj = new StringJoiner(",", "{", "}");
        StringJoiner other = new StringJoiner(":", "[", "]");
        Stream.of("a", "b", "c").forEachOrdered(sj::add);
        Stream.of("d", "e", "f").forEachOrdered(other::add);

        sj.merge(other);
        assertEquals(sj.toString(), "{a,b,c,d:e:f}");
    }

    public void testMergeSelf() {
        final StringJoiner sj = new StringJoiner(",", "[", "]").add("a").add("b");
        assertEquals(sj.merge(sj).toString(), "[a,b,a,b]");
        assertEquals(sj.merge(sj).toString(), "[a,b,a,b,a,b,a,b]");

        final StringJoiner sj2 = new StringJoiner(",").add("c").add("d");
        assertEquals(sj2.merge(sj2).toString(), "c,d,c,d");
    }
}