Converting perl snippet to java

I want to rewrite a perl code in java:

sub validate_and_fix_regex {
    my $regex = $_[0];
    eval { qr/$regex/ };
    if ($@) {
        $regex = rquote($regex);
    }
    return $regex;
}

sub rquote {
    my $string = $_[0] || return;
    $string =~ s/([^A-Za-z_0-9 "'\\])/\\$1/g;
    return $string;
}

the code gets a regex and fix it if it has any escaped character. i cant find any alternative for eval { qr/$regex/ }; and $string =~ s/([^A-Za-z_0-9 "'\\])/\\$1/g; in java.