Test to show what happens if you don't close Files.lines()

Test2.java

package utility;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Date;
import java.util.stream.Stream;

public class Test2 {
    public static void main(String[] args) throws IOException{
        int times = 100_000;

        Path path = Paths.get("/tmp", "date.txt");
        Test2 t2 = new Test2();
        t2.setDate(path);

        for (int i = 0; i < times; i++) {
            t2.run1(path);
        }
        for (int i = 0; i < times; i++) {
            t2.run2(path);
        }
        for (int i = 0; i < times; i++) {
            t2.run3(path);  //throws exception too many files open
        }
        System.out.println("finished");
    }

    public String run1(Path path){
        try(BufferedReader br = new BufferedReader(new FileReader(path.toFile()))){
            return br.readLine();
        } catch (IOException e) {
            throw new AssertionError(e);
        }
    }

    public String run2(Path path){
        try(Stream<String> stream = Files.lines(path)) {
            return stream.findFirst().get();
        } catch (IOException e) {
            throw new AssertionError(e);
        }
    }

    public String run3(Path path) throws IOException{
        return Files.lines(path).findFirst().get();
    }

    public void setDate(Path path) {
        try (FileWriter writer = new FileWriter(path.toFile())){
            writer.write(new Date().toString());
            writer.flush();
        } catch (IOException e) {
            throw new AssertionError(e);
        }
    }
}