src/java.base/share/classes/java/lang/Class.java

*** 236,254 ****
                  sb.append(getName());
              }
  
              TypeVariable<?>[] typeparms = component.getTypeParameters();
              if (typeparms.length > 0) {
!                 boolean first = true;
!                 sb.append('<');
                  for(TypeVariable<?> typeparm: typeparms) {
!                     if (!first)
!                         sb.append(',');
!                     sb.append(typeparm.getTypeName());
!                     first = false;
                  }
!                 sb.append('>');
              }
  
              for (int i = 0; i < arrayDepth; i++)
                  sb.append("[]");
  
--- 236,250 ----
                  sb.append(getName());
              }
  
              TypeVariable<?>[] typeparms = component.getTypeParameters();
              if (typeparms.length > 0) {
!                 StringJoiner sj = new StringJoiner(",", "<", ">");
                  for(TypeVariable<?> typeparm: typeparms) {
!                     sj.add(typeparm.getTypeName());
                  }
!                 sb.append(sj.toString());
              }
  
              for (int i = 0; i < arrayDepth; i++)
                  sb.append("[]");