run.pl

#!/usr/bin/env perl

use strict;
use warnings;
use utf8;

print "daemon pid: $$\n";

while (1) {
    my $pid = fork;

    die "Failed to fork" unless defined $pid;

    if ($pid <= 0) {
        # child
        exec("java Sig");
    }

    # parent
    $SIG{HUP} = sub {
        kill 'HUP', $pid;
    };

    waitpid $pid, 0;
}

__END__

Sig.java

public class Sig {
    public static void main(String... args) {
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            System.out.println("java finished");
            while (true) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                }
            }
        }));

        while (true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
        }
    }
}