GH-2037: Keep writer size available after close - #3805

import java.nio.file.Files;
import java.nio.file.Path;
import org.apache.parquet.example.data.Group;
import org.apache.parquet.example.data.simple.SimpleGroup;
import org.apache.parquet.hadoop.ParquetWriter;
import org.apache.parquet.hadoop.example.ExampleParquetWriter;
import org.apache.parquet.io.LocalOutputFile;
import org.apache.parquet.schema.MessageType;
import org.apache.parquet.schema.MessageTypeParser;

class WriterSizeProbe {
  public static void main(String[] args) throws Exception {
    Path path = Path.of(args[0]);
    MessageType schema = MessageTypeParser.parseMessageType("message test { required int32 value; }");
    ParquetWriter<Group> writer = ExampleParquetWriter.builder(new LocalOutputFile(path))
        .withType(schema).build();
    writer.write(new SimpleGroup(schema).append("value", 7));
    writer.close();
    try {
      long reported = writer.getDataSize();
      long actual = Files.size(path);
      System.out.printf("reported=%d, file=%d%n", reported, actual);
      if (reported != actual) {
        throw new AssertionError("Reported size differs from the completed file");
      }
    } catch (NullPointerException failure) {
      System.out.println(failure);
    }
  }
}