wrapper method that evaluates toString dynamically, useful in performance sensitive logging

log-with-supplier

#!java --source 11
import java.util.function.Supplier;
import java.util.List;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.stream.Stream;

public class LogWithSuplier {

  public static void main(String... args) throws IOException {
    for (var arg : args) {
      List<String> lines = Files.readAllLines(new File(arg).toPath());
      System.out.printf("Lines read: %s", supplied(() -> lines.size())).println();
    }

  }

  private static Object supplied(Supplier s) {
    return new Object() {
      @Override
      public String toString() {
        return s.get().toString();
      }
    };
  }
}