debugging - Java: try(Scanner scan = new Scanner(System.in) { } causing an exception -

using try(scanner scan = new scanner(system.in)) { } causing

exception in thread "main" java.util.nosuchelementexception

when try debug says

variable information not available, source compiled without -g option.

and shows below code

    public scanner(inputstream source) {     this(new inputstreamreader(source), whitespace_pattern);   } 

one of methods uses line:

protected string loginname(){     string username;     string password;     try (scanner scan = new scanner(system.in)) { // line causing error.       system.out.print("enter username: ");       username = scan.next();       system.out.print("enter password: ");       password = scan.next();     }     if(getusernameslist().contains(username))          if(password.equals(getpasswordslist().get(getusernameslist().indexof(username)))) return username;         else return "-1";      else return "-1"; } 

you're closing system.in (a global-variable). please, not that. everywhere have

try(scanner scan = new scanner(system.in)) 

guarantees system.in close(d). once it's close(d) can't read again (or mentioned exception). also, can compile debug symbols (or step ide's built-in debugger or jdb applicable). scanner.close() javadoc says (in part),

if scanner has not yet been closed if underlying readable implements closeable interface readable's close method invoked