java - Scanner in loop never stops reading inputs -


my code below supposed prompting user numbers. part works, after user inputs numbers, nothing happens. why code stop after user inputs numbers?

public static void main(string[] args) {     arraylist<double> inputs = getnumbers();     int numberofitemstodrop = getlowestnumber();     // ... }   public static arraylist<double> getnumbers() {     arraylist<double> inputs = new arraylist <double> ();      scanner in = new scanner(system.in);     system.out.println("please enter 5 ten numbers on 1 line separated spaces.");     double vals = in.nextdouble();      while (in.hasnextdouble()) {         inputs.add(in.nextdouble());     }      return inputs; }   public static int getlowestnumber() {     int numberofitemstodrop = 0;      system.out.println("how many of lowest values should dropped?");     scanner in = new scanner(system.in);     numberofitemstodrop = in.nextint();      return numberofitemstodrop; }

you have 2 problems: scanner, , indistinguishable inputs.

in order appear in code...

1. dueling scanners

as general rule, want 1 scanner per input stream. if first scanner "reads ahead" fill input buffer, bytes vanish forever when scanner gets garbage-collected. typically leads nosuchelementexception when next scanner tries read inputs no longer exist.

note not same trying read closed input stream (see "java.util.nosuchelementexception - scanner reading user input") --- losing inputs can happen when input stream still open.

a better strategy create 1 scanner, , pass each method needs read it:

public static void main(final string[] args) {     final scanner in = new scanner(system.in);  // 1 , only.     arraylist<double> inputs = getnumbers(in);     int numbertodrop = getlowestnumber(in);     // ... }

2. indistinguishable inputs

also, need way determine end of floating-point data , start of integer. can't hasnextdouble, because integer input 3 double. fortunately, have told user read end of line, , nextline that.

i created throw-away scanner read double values string returned nextline. (the new scanner parser not conflict scanner in, because read different sources.)

public static arraylist<double> getnumbers(final scanner in) {     system.out.println(       "please enter 5 ten numbers on 1 line " +       "separated spaces."     );     final string s = in.nextline();     final scanner parser = new scanner(s);     arraylist<double> inputs = new arraylist<>();     while (parser.hasnextdouble()) {         inputs.add(parser.nextdouble());     }     parser.close();     return inputs; }

i checked input hasnextint , returned 0 if wasn't valid integer:

public static int getlowestnumber(final scanner in) {     system.out.println(       "how many of lowest values should dropped?"     );     if (in.hasnextint()) {         return in.nextint();     }     return 0; }

i think both of scanning methods should throw exceptions if encounter bogus inputs, rather trying make this... thing worse bogus data plausible result based on bogus data.


Comments

Post a Comment

Popular posts from this blog

node.js - Node js - Trying to send POST request, but it is not loading javascript content -

i have been trying send post request website, , has not been loading full site. i guessing problem node js not loading javascript content, executing it. can see javascript in response, though never loads content javascript files producing in html. what mean is, doesn't execute javascript. how make node js code overcome this, , wait the full website load? have tried native code, , "request' module, both producing same errors. if helps, don't need native javascript. modules fine. some code have tried (request module): var options = { method: 'post', uri: 'https://url', formdata: { 'email': 'email', 'prize': '0', 'transactional': 'on' }, headers: { /* 'content-type': 'application/x-www-form-urlencoded' */ // set automatically } }; rp(options) .then(function (body) { console.log(body) }) .catch(function (err) { console.log(err) }); when fetch content...
Read more

javascript - Replicate keyboard event with html button -

i have tried few ways make happen. have javascript pinball game uses keyboard keys controls. converting application touch screen display. workaround, hoping overlay buttons when clicked simulate keyboard strokes. have done research , sounds should work. using jquery v3.2.1 here things have tried far... html element: <input type="button" class="coil"></input> $('.coil').trigger({type: 'keydown', which: 40, keycode: 40}); with this, not errors, nothing happens. var coilkey = $('body').keydown(function(e) { switch (e.keycode) { case 40: break;} }) $('.coil').click(coilkey); this 1 returns error in console... ((jquery.event.special[handleobj.origtype] || (intermediate value)).handle || handleobj.handler).apply not function below javascript game engine handles key listeners... addkeylistener: function (keyandlistener) { this.keylisteners.push(keyandlistener); }, // gi...
Read more

javascript - Web audio api 5.1 surround example not working in firefox -

i've been playing lott lately web audio api on both firefox , chrome. few days ago started experiment surround set. when trying surround audio in web audio api came notice example works fine in chrome v59 not in firefox v54. // create web audio api context var audioctx = new (window.audiocontext || window.webkitaudiocontext)(); audioctx.destination.channelinterpretation = 'discrete'; audioctx.destination.channelcountmode = 'explicit'; audioctx.destination.channelcount = 6; var oscillators = []; var merger = audioctx.createchannelmerger(6); console.log(audioctx.destination, merger); //merger.channelinterpretation = 'discrete'; //merger.channelcountmode = 'explicit'; //merger.channelcount = 6; var addoscilator = function(channel, frequency) { var oscillator = audioctx.createoscillator(); oscillator.frequency.value = frequency; // value in hertz oscillator.connect(merger,0,channel); oscillator.start(); oscillators.push(o...
Read more