test/java/util/StringJoiner/MergeTest.java

rev 7730 : 8020977: StringJoiner merges with itself not as expected
Reviewed-by:

*** 21,31 ****
   * questions.
   */
  
  /**
   * @test
!  * @bug 8017231
   * @summary test  StringJoiner::merge
   * @run testng MergeTest
   */
  
  import java.util.StringJoiner;
--- 21,31 ----
   * questions.
   */
  
  /**
   * @test
!  * @bug 8017231 8020977
   * @summary test  StringJoiner::merge
   * @run testng MergeTest
   */
  
  import java.util.StringJoiner;
*** 119,124 ****
--- 119,133 ----
          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");
+     }
  }
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