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Stuck with detecting next line from console

I am banging my head to the wall but just can't figure out what is going wrong. Simple program but not working. I need to get 3 inputs(integers) from user. End the program on either array full or when user presses enter. Here is what i am trying without any luck. It works fine all the situtations EXCEPT it cant detect nextline.
Scanner sc = new Scanner(System.in);
int[] intArray = new int[3];
int counter = 0;
System.out.println("Start!!");
while (true) {
System.out.println("Enter int");
if (sc.hasNextInt() && counter <= 2) {
intArray[counter] = sc.nextInt();
counter++;
} else {
if (counter >= 3) {
System.out.println("Array is full");
System.out.println("Array ELemnets : " + Arrays.toString(intArray));
break;
}
if (sc.next().isEmpty() || sc.next().equals("\n")){
System.out.println("Its empty");
break;
} else {
System.out.println("wrong input.");
}
}
}
sc.close();
Please help me . Why is it not detecting next line. I have googled already and tried lot of solutions provided but none worked for me. Any HELP!!!
Thanks
Edited code :
Scanner sc = new Scanner(System.in);
int[] intArray = new int[3];
int counter = 0;
System.out.println("Start!!");
while (true) {
System.out.println("Enter int");
if (sc.hasNextInt() && counter <= 2) {
intArray[counter] = sc.nextInt();
counter++;
} else {
if (counter >= 3) {
System.out.println("Array is full");
System.out.println("Array ELemnets : " + Arrays.toString(intArray));
break;
}
String next = sc.next();
if (next.isEmpty() || next.equals("\n"))
{
System.out.println("Its empty");
break;
} else {
System.out.println("wrong input.");
}
}
}
sc.close();
}

int[] intArray = new int[3];
int counter = 0;
boolean enterPressed = false; // added boolean to test if they entered a blank line
try (
Scanner sc = new Scanner(System.in); // declaring in a try-with-resources, so it automatically closes.
) {
System.out.println("Start!!");
System.out.println("Enter int"); // Have to print this the first time
while (counter < 3 && !enterPressed) {
if (counter > 0) { System.out.println("Enter int"); }
String next = sc.nextLine(); // just grab a line (the user pressed enter)
if (next.isEmpty()) {
enterPressed = true;
} else {
try {
intArray[counter] = Integer.parseInt(next);
counter++;
} catch (NumberFormatException ex) {
System.out.println("wrong input.");
}
}
}
}

Your code is sticking because it's waiting on the conditional check for sc.hasNextInt(). The solution I propose below, manually parses the user-input string to see if it's an int, rather than using the Scanner's functionality to check if it's an int or not.
I left some comments in the code to hopefully add clarity. Let me know if anything doesn't make sense, and I'm happy to elaborate!
import java.util.Arrays;
import java.util.Scanner;
public class ScannerTestNew {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int[] intArray = new int[3];
int counter = 0;
System.out.println("Start!!");
// Variable used to hold the user's input via the Scanner.
String userInput = null;
while (true) {
System.out.print("Enter an integer: ");
userInput = sc.nextLine();
// Check to see if an empty string/enter/return has been input:
if (userInput.length() == 0) {
System.out.println("Input is empty!");
break;
}
// Checking to see if the input can be parsed into an int. If it can't, retry.
int intInput = 0;
try {
intInput = Integer.parseInt(userInput);
} catch (NumberFormatException e) {
System.out.println("Invalid input for type Integer. Please try again.");
continue;
}
// We know we have an int at this point. Checking that the array isn't already
// filled.
if (counter <= 2) {
intArray[counter] = intInput;
counter++;
// The array is filled, act accordingly.
} else if (counter > 2) {
System.out.println("Array is full.");
System.out.printf("Array Elements: %s", Arrays.toString(intArray));
break;
}
sc.close();
}
}
}

Loop in a loop and If statement?

I am a beginner programming, I want to ask multiple questions using arrays and tell the user whether he got each question right or wrong, which I managed to get it running, but now how do I implement the code so that the user will only have up to 3 attempts to get a question right.
for(int n = 0; n <QArray.length; n++)
{
System.out.println("Question" + (n+1));
System.out.println(QArray[n]);
String ans = scanner.nextLine();
if (ans.equalsIgnoreCase(AArray[n]))
{
System.out.println("That is correct!");
}
else
{
System.out.println("That is incorrect!");
}
}

So if I correctly understand your goal, you've a list of questions, and whilst they have made fewer than three failed attempts at them, you would like for the users to get to try and answer them?
Using your existing style, you could do something like
for(int n = 0; n < QArray.length; n++)
{
System.out.println("Question" + (n+1));
System.out.println(QArray[n]);
int incorrectAnswers = 0;
while(incorrectAnswers < 3)
{
String ans = scanner.nextLine();
if (ans.equalsIgnoreCase(AArray[n]))
{
System.out.println("That is correct!");
break;
}
else
{
System.out.println("That is incorrect!");
incorrectAnswers++;
}
}
}
Depending how the data is displayed and transferred and concerns regarding security etc, it would make for easier to manage code to have a QuestionAnswer object that contains the question and the answer, as well as a method for what constitutes a valid answer (e.g. case insensitive, or maybe you want to accept multiple words etc, whatever works for your case), so you could end up with code that looks like the below.
for(int i = 0; i < questionAnswerArray.length; i++)
{
QuestionAnswer qa = questionAnswerArray[i];
System.out.println("Question " + (i+1));
System.out.println(qa.getQuestion());
int incorrectAnswers = 0;
while(incorrectAnswers < 3)
{
String ans = scanner.nextLine();
if (qa.isValidAnswer(ans))
{
System.out.println("That is correct!");
break;
}
else
{
System.out.println("That is incorrect!");
incorrectAnswers++;
}
}
}

Try to use while with the number of attempt you need:
for (int n = 0; n < QArray.length; n++) {
System.out.println("Question" + (n + 1));
System.out.println(QArray[n]);
int attempt = 3;
while (attempt > 0) {
System.out.print("Please enter the answer: ");
String ans = scanner.nextLine();
if (ans.equalsIgnoreCase(AArray[n])) {
System.out.println("That is correct!");
break;
} else {
System.out.println("That is incorrect!");
}
attempt--;
}
}

Put a second loop inside the first.
for(int n = 0; n < QArray.length; n++) {
boolean correct = false;
for(int m = 0; m < 3; m ++) {
String ans = scanner.nextLine();
if (ans.equalsIgnoreCase(AArray[n])) {
System.out.println("That is correct!");
correct = true;
break;
} else {
System.out.println("That is incorrect!");
}
}
if(!correct) {
//something
} else {
//something else
}
}
Note the break;. That command will exit the inner for-loop (which contains the scanner input) when a correct answer is submitted. If the user doesn't get the right answer in 3 tries, the for-loop will end by reaching the end of its counter.

Applying do while loops

My code is currently unable to start at the beginning of the program which is 'Please type in...'. I want the code to be able to return to the beginning statement everytime choice 1 or 2 is executed. The while statement does not satisfy this as I cant use the while statement before 'choice' is declared. I understand that I'm suppose to be using a do while loop but everytime I try to implement it - it gives me an error with braces.
The following is a snippet of my code:
System.out.println("Please type in 1 for a customer to view their portfolio, 2 to trade stocks or 3 to exit the application");
int choice = Integer.parseInt(input.nextLine());
{
while (!"3".equals(choice));
{
if (choice == 1) {
System.out.println(mycustomers[menuchoice].toString());
return;
}
if (choice == 2) {
String StockSelect = "Please select a stock";
for (int i = 0; i < mystocks.length; i++) {
// [i] is the element we are accessing
StockSelect += " " + i + " " + (mystocks[i].getSymbol());
}
System.out.println(StockSelect);
int stockchoice = Integer.parseInt(input.nextLine());
System.out.println("Select 1 to buy or 2 to sell?");
int choice2 = Integer.parseInt(input.nextLine());
if (choice2 == 1) {
System.out.println("How many stocks would you like to buy ");
int volumebought = Integer.parseInt(input.nextLine());
for (int i = 0; i < numofstocks; i++) {
mycustomers[menuchoice].setBalance(
mycustomers[menuchoice].getBalance() - (volumebought * mystocks[i].getprice()));
mycustomers[menuchoice].setPortfolio();
}
System.out.println(mycustomers[menuchoice].toString());
return;
}
if (choice2 == 2) {
System.out.println("How much stocks would you like to sell ");
int volumesold = Integer.parseInt(input.nextLine());
for (int i = 0; i < numofstocks; i++) {
mycustomers[menuchoice].setBalance(
mycustomers[menuchoice].getBalance() + (volumesold * mystocks[i].getprice()));
mycustomers[menuchoice].setPortfolio();
}
System.out.println(mycustomers[menuchoice].toString());
return;
}
}
if (choice == 3) // how to exit application
{
System.out.println("Thank you for using the application");
System.out.println("The current state of all customers are:");
for (int i = 0; i < mycustomers.length; i++) {
System.out.println(mycustomers[i].toString());
}
System.out.println("The current state of all stocks are:");
for (int i = 0; i < mystocks.length; i++) {
System.out.println(mystocks[i].toString());
}
System.exit(0);
}
}
}}}
How would I implement the do-while loop so that it goes back to the initial statement every time after executing the code - if only if the input is not 3?

Ask for input inside the while loop, like this:
choice = Integer.parseInt(input.nextLine());

How to add for loops to if statements?

In my code below I am not sure what order to put it in to work properly.
I first want it to print out for the user to select an option which it does, then if they select 1 it asks them their name and verifies it with the loop etc.
When I enter a name it starts to just loop the question enter your name and I don't know how to fix it.
Do I need to add more statements to my program, if I do then can I still use if statements for the user to select an option?
import java.util.Scanner;
public class username {
public static void main(String[] args) {
{
int UseLift;
int AuditReport;
int ExitLift;
int a;
UseLift = 1;
AuditReport = 2;
ExitLift = 3;
}
System.out.println("choose an option");
System.out.println("Uselift(1)");
System.out.println("see audit report(2)");
System.out.println("Exit Lift(3)");
Scanner d = new Scanner(System.in);
int a = d.nextInt();
Scanner kb = new Scanner(System.in);
// array containing usernames
String[] name = {"barry", "matty", "olly", "joey"}; // elements in array
if (a == 1) {
System.out.println(" Enter your name ");
}
String name1 = kb.nextLine();
boolean b = true;
int j = 0;// counter will start at 0
outerloop:
while (j < 3) {
System.out.println("Enter your name");
}
for (int i = 0; i < name.length; i++) {
if (name[i].equals(name1)) {
System.out.println("you are verified you may use the lift, calling lift ");
}
break;// to stop loop checking names
}
System.out.println("Username Invalid");
j++;
if (a == 2) {
System.out.println("");
}
if (a == 3) {
System.out.println(" Please Exit Lift ");
}
}
}

here you go:
public static void main(String... args) {
String[] verifiedNames = { "barry", "matty", "olly", "joey" };
System.out.println("choose an option");
System.out.println("Uselift(1)");
System.out.println("see audit report(2)");
System.out.println("Exit Lift(3)");
Scanner scanner = new Scanner(System.in);
int choice = scanner.nextInt();
switch (choice) {
case 1:
scanner.nextLine(); // get '\n' symbol from previous input
int nameAttemptsLeft = 3;
while (nameAttemptsLeft-- > 0) {
System.out.println(" Enter your name ");
String name = scanner.nextLine();
if (Arrays.asList(verifiedNames).contains(name)) {
System.out.println("dear " + name + " you are verified " +
"you may use the lift, calling lift ");
break; // break out of loop
}
}
if (nameAttemptsLeft < 0) {
System.out.println("Username Invalid");
}
break;
case 2:
System.out.println("option 2");
break;
case 3:
System.out.println(" Please Exit Lift ");
break;
}
scanner.close();
}

Your while loop below:
while (j < 3) {
System.out.println("Enter your name");
}
will loop forever since j is not incrementing (j++). I believe you've mis-matched your curly braces at some point.

.length error when trying to use a for loop with an ArrayList

First off I'm sorry for the title I couldn't think of a better way to word it. The actual error is in option 3(whenever I try to add together all the sales in option 1). When I try to use salesList.length to track the size of the array I get cannot find symbol- variable length I'm very new to using array lists and that method worked for me in an earlier array but that array wasn't dynamic. Is there a specific way to track the length of a dynamic array list?
import java.util.*;
public class CustomerTest
{
public static void main(String[] args)
{
double totalSales = 0;
ArrayList<String> nameList;
nameList = new ArrayList<String>();
ArrayList<Double> salesList;
salesList = new ArrayList<Double>();
Scanner myScanner = new Scanner(System.in);
boolean done = true;
do
{
System.out.println("1) Add a new customer \n 2) Print all customers \n 3) Compute and print the total sales \n 4) Quit");
int choice = Integer.parseInt(myScanner.nextLine());
if (choice == 1)
{
System.out.print("Add a new customer ");
String answer = myScanner.nextLine();
nameList.add(answer);
System.out.print("Enter their sales ");
String answer2 = myScanner.nextLine();
double answer3 = Double.parseDouble(answer2);
salesList.add(answer3);
}
else if(choice == 2)
{
System.out.println("Customers: " + nameList);
System.out.println("Sales: " + salesList);
}
else if(choice == 3)
{
for(int i = 0; i < salesList.length; i++)
{
totalSales = totalSales + salesList[i];
}
System.out.println(totalSales);
}
else if(choice == 4)
{
System.out.println("Goodbye *Bows gracefully*");
done = false;
}
else
System.out.println("Invalid Choice");
}
while (done);
System.exit(0);
}
}

Change it to salesList.size();. Unlike arrays, the length of an ArrayList is not a directly accessible field.

Array have the length field
ArrayList doesnot have the length field type Use size()

use salesList.size(). unlike arrays you cannot use salesList.lenght

else if (choice == 3) {
for (int i = 0; i < salesList.size(); i++) {
totalSales += salesList.get(i);
}
System.out.println(totalSales);
}
Replace choice 3 with this and it should work.

your code is having bugs: Change the else if(choice==3) {} conditional part to following. you cannot use salesList.length, it can be done using salesList.size() and pleas change salesList[i] to salesList.get(i).
else if(choice == 3)
{
for(int i = 0; i < salesList.size(); i++)
{
totalSales += salesList.get(i);
}
System.out.println(totalSales);
}