src/java.base/share/classes/sun/reflect/generics/reflectiveObjects/WildcardTypeImpl.java

*** 30,39 ****
--- 30,40 ----
  import java.lang.reflect.WildcardType;
  import sun.reflect.generics.factory.GenericsFactory;
  import sun.reflect.generics.tree.FieldTypeSignature;
  import sun.reflect.generics.visitor.Reifier;
  import java.util.Arrays;
+ import java.util.StringJoiner;
  
  
  /**
   * Implementation of WildcardType interface for core reflection.
   */
*** 154,171 ****
                  return "?";
          }
  
          assert bounds.length > 0;
  
-         boolean first = true;
-         for(Type bound: bounds) {
-             if (!first)
-                 sb.append(" & ");
  
!             first = false;
!             sb.append(bound.getTypeName());
          }
          return sb.toString();
      }
  
      @Override
      public boolean equals(Object o) {
--- 155,171 ----
                  return "?";
          }
  
          assert bounds.length > 0;
  
  
!         StringJoiner sj = new StringJoiner(" & ");
!         for(Type bound: bounds) {
!             sj.add(bound.getTypeName());
          }
+         sb.append(sj.toString());
+ 
          return sb.toString();
      }
  
      @Override
      public boolean equals(Object o) {