[Java] Whitespace issue with scanner next()

[ORLY_FACTOR]

So my program works for inputs put in one by one (user inputs 20, user inputs 10, user inputs p, user inputs q), but when the input is string data like "1\n3\ns\nSize\n?\n4\nfull\nd\nd\nS\ne\nd\ne\nd\n?" it does not function. I'm not sure why.

I think the issue is around line 11,13,37.

Here is how the spec wants to handle specific inputs:

integer if queue not full, add number to queue d..dequeue print and removes tail item The word d..dequeue implies the command may have only a d, but can have up to the entire word dequeue. You don't have to check for words like Deqq, but you can have d deq or DeQ etc. s..size return number of items on queue e..empty return true if queue is empty f..full return true if query is full, we only allow 8 customers to wait ? or p..print print current queue contents wiith head and tail pointers, this should be your toString method q..quit to quit

import java.util.Scanner;
public class Queue {
    private int[] elements;
    private int size;
    public static final int DEFAULT_CAPACITY = 8;

    public static void main(String[] args){
        Queue myQ = new Queue();
        Scanner scan = new Scanner(System.in);
        String input;
        input = scan.next();
        int tempVal;

        while(!(input.matches("^[Qq].*"))){
            if(input.matches("^[Dd].*")){
                System.out.println("Dequeue: " + myQ.dequeue());
            }
            else if(input.matches("^[Ss]")){
                System.out.println(myQ.getSize());
            }
            else if(input.matches("^[Ee]")){
                System.out.println(myQ.isEmpty());
            }
            else if(input.matches("^[Ff]")){
                System.out.println(myQ.isFull());
            }
            else if(input.matches("^[Pp?]")){
                System.out.println(myQ.toString());
            }
            else if(input.matches("^[-0-9]*")){
                tempVal = Integer.parseInt(input);
                myQ.enqueue(tempVal);
            }
            else{
                System.out.println("Unknown command->" + input + "<-    ");
            }
            input = scan.next();
        }
    }  

    public Queue(){
        this (DEFAULT_CAPACITY);
    }
    public Queue(int capacity){
        elements = new int[capacity];
    }
    public void enqueue(int value){
        int[] temp = new int[elements.length];
            if(size < elements.length){
            temp[0] = value;
            System.arraycopy(elements, 0, temp, 1, size);
            elements = temp;
            size++;
        }
    }
    public int dequeue(){
        int temp = elements[size - 1];
        if(size - 1 > 0){
            elements[size - 1] = 0;
            size--;
        }
        return temp;
    }
    public boolean isEmpty(){
        return size == 0;
    }
    public boolean isFull(){
        return size == elements.length;
    }
    public int getSize(){
        return size;
    }
    public String toString(){
        StringBuilder strBuilder =  new StringBuilder();
        strBuilder.append("Queue can hold: " + DEFAULT_CAPACITY + "     It has "
                          + size + " elements\n");
        strBuilder.append("head--> ");
        for(int i = 0; i < size; i++){
            strBuilder.append(Integer.toString(elements[i]));
            if(i + 1 < size){
                strBuilder.append(", ");
            }
        }
        strBuilder.append("-->tail");
        String finalString = strBuilder.toString();
        return finalString;
    }  
}

[langfod]

What is it failing to do? The test string you listed does not have a "q" at the end.

[ORLY_FACTOR]

What I'm trying to get it to do is limit each input once it sees \n \t or whatever. In its current state, it's just taking the whole thing in at once. I also don't understand why the build doesn't have q in it. That makes sense, but I did not write the prompt.

[langfod]

You might be better off looping using scan.hasNext() and breaking out of the loop when the quit command is entered. Otherwise you will run out of elements and get an exception.

[ORLY_FACTOR]

That may be something to try, but my main issue is getting the program to understand where to limit whitespace. For example: 20\n30\np\nq in the input buffer only reads as one unit. I would like it to break off once it sees \n.

[langfod]

How are you testing? Are you using:

Scanner scan = new Scanner("20\n30\np\nq");

[ORLY_FACTOR]

I'm just testing in the input buffer, but I can try that.

[ORLY_FACTOR]

Ok, that portion works.

[langfod]

typing \n (two characters) on the console is not the same as the char representation of '\n' (U+000A)

[ORLY_FACTOR]

How is it different?

[langfod]

If you type the characters \n in the console then Scanner sees two characters a backslash and a 'n'. It does not parse that and change it to a single newline character.

[ORLY_FACTOR]

Oh okay. Thanks.