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how to remove input buffer from java [duplicate]

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Scanner is skipping nextLine() after using next() or nextFoo()?
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Closed 4 years ago.
I'm trying to input a certain number of strings but the last input gets a new line as input automatically. I need to remove the input buffer plz help
Scanner input = new Scanner(System.in);
int n = input.nextInt(); //n is my input number
String[] arr = new String[n];
int i,j;
for(i=0;i<n;i++)
{
arr[i] = input.nextLine();
}
If I enter n=5 as input and when i print the array my last input string goes missing and is replaced by a new line character

Just consume the new line character after the first int:
Scanner input = new Scanner(System.in);
int n = input.nextInt(); //n is my input number
input.nextLine();
String[] arr = new String[n];
int i,j;
for(i=0;i<n;i++)
{
arr[i] = input.nextLine();
}
Demo to make sure we agree on what the code should be doing:
public static void main(String[] args) {
String text =
"5\n" +
"line 1\n" +
"line 2\n" +
"line 3\n" +
"line 4\n" +
"line 5\n" +
"line 6\n";
Scanner input = new Scanner(new ByteArrayInputStream(text.getBytes()));
int n = input.nextInt(); //n is my input number
input.nextLine();
String[] arr = new String[n];
for(int i = 0; i < n; i++) {
arr[i] = input.nextLine();
}
System.out.println(Arrays.asList(arr)); // [line 1, line 2, line 3, line 4, line 5]
}

The call to nextInt() won't consume the new line you enter in the console, so you can consume the extra newline by using Scanner.nextLine() instead of nextInt() and converting it to an int.
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
//Convert the int to a String
int n = Integer.parseInt(input.nextLine());//n is my input number
String[] arr = new String[n];
int i, j;
for (i = 0; i < n; i++) {
arr[i] = input.nextLine();
}
for (String s : arr) {
System.out.println(s);
}
}

Scanner.nextInt() only consumes the integer that is given during input. So, if you provide an integer as input say 5 and press enter, then Scanner.nextInt() will only consume 5 and the enter/return is passed onto nextLine. This is why you think, that you are able to input 1 less.
So, after Scanner.nextInt(), you should add a Scanner.nextLine() just to consume the enter/return key

How to read multiple integer values from one line in Java using BufferedReader object?

I am using BufferedReader class to read inputs in my Java program.
I want to read inputs from a user who can enter multiple integer data in single line with space.
I want to read all these data in an integer array.
Input format-
the user first enters how many numbers he/she want to enter
And then multiple integer values in the next single line-
INPUT:
5
2 456 43 21 12
Now, I read input using an object (br) of BufferedReader
int numberOfInputs = Integer.parseInt(br.readLine());
Next, I want to read next line inputs in an array
int a[] = new int[n];
But we cannot read using this technique
for(int i=0;i<n;i++)
{
a[i]=Integer.parseInt(br.readLine()); //won't work
}
So, is there any solution to my problem or we can't just read multiple integers from one line using BufferedReader objects
Because using Scanner object we can read this type of input
for(int i=0;i<n;i++)
{
a[i]=in.nextInt(); //will work..... 'in' is object of Scanner class
}

Try the next:
int a[] = new int[n];
String line = br.readLine(); // to read multiple integers line
String[] strs = line.trim().split("\\s+");
for (int i = 0; i < n; i++) {
a[i] = Integer.parseInt(strs[i]);
}

Late to the party but you can do this in one liner in Java 8 using streams.
InputStreamReader isr= new InputStreamReader();
BufferedReader br= new BufferedReader(isr);
int[] input = Arrays.stream(br.readLine().split("\\s+")).mapToInt(Integer::parseInt).toArray();

If you want to read integers and you didn't know number of integers
String[] integersInString = br.readLine().split(" ");
int a[] = new int[integersInString.length];
for (int i = 0; i < integersInString.length; i++) {
a[i] = Integer.parseInt(integersInString[i]);
}

Integer.parseInt(br.readLine()) -> Reads a whole line and then converts it to Integers.
scanner.nextInt() -> Reads every single token one by one within a single line then tries to convert it to integer.
String[] in = br.readLine().trim().split("\\s+");
// above code reads the whole line, trims the extra spaces
// before or after each element until one space left,
// splits each token according to the space and store each token as an element of the string array.
for(int i = 0; i < n; i++)
arr[i] = Integer.parseInt(in[i]);
// Converts each element in the string array as an integer and stores it in an integer array.

import java.io.*;
public class HelloWorld{
public static void main(String []args){
int i;
System.out.println("enter the array element");
InputStreamReader isr= new InputStreamReader();
BufferedReader ib= new BufferedReader(isr);
int a[]=new int [5];
for(i=0;i<5;i++)
{
a[i]= Integer.parseInt(ib.readLine(a[i]));
}
for(i=0;i<5;i++)
{
System.out.println(a[i]);
}
}
}

I use this code for List:
List<Integer> numbers = Stream.of(reader.readLine().split("\\s+")).map(Integer::valueOf).collect(Collectors.toList());
And it is almost the same for array:
int[] numbersArray = Arrays.stream(reader.readLine().split("\\s+")).mapToInt(Integer::valueOf).toArray();

You can use StringTokenizer class of java.util package. The StringTokenizer class allows an application to break a string into tokens. You can use this tokens using nextToken() method of StringTokenizer class.
You can use following constructor of StringTokenizer:
StringTokenizer(String str, String delimiter);
you can use space(" ") as delemeter.
int a[] = new int[N];
StringTokenizer st = new StringTokenizer(br.readLine() , " ");
for(int i=0 ; i<N ; i++) {
a[i] = Integer.parseInt(st.nextToken());
}

Well as you mentioned there are two lines-
First line takes number of integers and second takes that many number
INPUT: 5 2 456 43 21 12
So to address this and covert it into array -
String[] strs = inputData.trim().split("\\s+"); //String with all inputs 5 2 456 43 21 12
int n= Integer.parseInt(strs[0]); //As you said first string contains the length
int a[] = new int[n]; //Initializing array of that length
for (int i = 0; i < n; i++)
{
a[i] = Integer.parseInt(strs[i+1]); // a[0] will be equal to a[1] and so on....
}

i/p:34 54
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st = new StringTokenizer(br.readLine()," ");
for(int i=0;i<st.countTokens();i++){
a=Integer.parseInt(st.nextToken());
b=Integer.parseInt(st.nextToken());
}
//For fast input output for one line

How to read array of integers from the standard input in Java?

in one line from the standard input I have 3 types of integers: the first integer is id, the second integer is N - some number, and after that follows N integers, separeted by a single space which I want to store in array or ArrayList. How can I do this using BufferedReader? I have the following code:
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String[] line = br.readLine().split(" ");
int ID = Integer.parseInt(line[0]);
int N = Integer.parseInt(line[1]);
My question is is there any elegant way to read the rest of the line and to store it into array?

Use Scanner and method hasNextInt()
Scanner scanner = new Scanner(System.in);
while (scanner.hasNext()) {
if (scanner.hasNextInt()) {
arr[i]=scanner.nextInt();
i++;
}
}

How can I do this using BufferedReader?
You've already read/split the line, so you can just loop over the rest of the inputted integers and add them to an array:
int[] array = new int[N]; // rest of the input
assert line.length + 2 == N; // or some other equivalent check
for (int i = 0; i < N; i++)
array[i] = Integer.parseInt(line[i + 2]);
This will also let you handle errors within the loop (I'll leave that part to you, should you find it necessary).

How to read multiple Integer values from a single line of input in Java?

I am working on a program and I want to allow a user to enter multiple integers when prompted. I have tried to use a scanner but I found that it only stores the first integer entered by the user. For example:
Enter multiple integers: 1 3 5
The scanner will only get the first integer 1. Is it possible to get all 3 different integers from one line and be able to use them later? These integers are the positions of data in a linked list I need to manipulate based on the users input. I cannot post my source code, but I wanted to know if this is possible.

I use it all the time on hackerrank/leetcode
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String lines = br.readLine();
String[] strs = lines.trim().split("\\s+");
for (int i = 0; i < strs.length; i++) {
a[i] = Integer.parseInt(strs[i]);
}

Try this
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (in.hasNext()) {
if (in.hasNextInt())
System.out.println(in.nextInt());
else
in.next();
}
}
By default, Scanner uses the delimiter pattern "\p{javaWhitespace}+" which matches at least one white space as delimiter. you don't have to do anything special.
If you want to match either whitespace(1 or more) or a comma, replace the Scanner invocation with this
Scanner in = new Scanner(System.in).useDelimiter("[,\\s+]");

You want to take the numbers in as a String and then use String.split(" ") to get the 3 numbers.
String input = scanner.nextLine(); // get the entire line after the prompt
String[] numbers = input.split(" "); // split by spaces
Each index of the array will hold a String representation of the numbers which can be made to be ints by Integer.parseInt()

Scanner has a method called hasNext():
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext())
{
System.out.println(scanner.nextInt());
}

If you know how much integers you will get, then you can use nextInt() method
For example
Scanner sc = new Scanner(System.in);
int[] integers = new int[3];
for(int i = 0; i < 3; i++)
{
integers[i] = sc.nextInt();
}

Java 8
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
int arr[] = Arrays.stream(in.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();

Here is how you would use the Scanner to process as many integers as the user would like to input and put all values into an array. However, you should only use this if you do not know how many integers the user will input. If you do know, you should simply use Scanner.nextInt() the number of times you would like to get an integer.
import java.util.Scanner; // imports class so we can use Scanner object
public class Test
{
public static void main( String[] args )
{
Scanner keyboard = new Scanner( System.in );
System.out.print("Enter numbers: ");
// This inputs the numbers and stores as one whole string value
// (e.g. if user entered 1 2 3, input = "1 2 3").
String input = keyboard.nextLine();
// This splits up the string every at every space and stores these
// values in an array called numbersStr. (e.g. if the input variable is
// "1 2 3", numbersStr would be {"1", "2", "3"} )
String[] numbersStr = input.split(" ");
// This makes an int[] array the same length as our string array
// called numbers. This is how we will store each number as an integer
// instead of a string when we have the values.
int[] numbers = new int[ numbersStr.length ];
// Starts a for loop which iterates through the whole array of the
// numbers as strings.
for ( int i = 0; i < numbersStr.length; i++ )
{
// Turns every value in the numbersStr array into an integer
// and puts it into the numbers array.
numbers[i] = Integer.parseInt( numbersStr[i] );
// OPTIONAL: Prints out each value in the numbers array.
System.out.print( numbers[i] + ", " );
}
System.out.println();
}
}

There is more than one way to do that but simple one is using String.split(" ")
this is a method of String class that separate words by a spacial character(s) like " " (space)
All we need to do is save this word in an Array of Strings.
Warning : you have to use scan.nextLine(); other ways its not going to work(Do not use scan.next();
String user_input = scan.nextLine();
String[] stringsArray = user_input.split(" ");
now we need to convert these strings to Integers. create a for loop and convert every single index of stringArray :
for (int i = 0; i < stringsArray.length; i++) {
int x = Integer.parseInt(stringsArray[i]);
// Do what you want to do with these int value here
}
Best way is converting the whole stringArray to an intArray :
int[] intArray = new int[stringsArray.length];
for (int i = 0; i < stringsArray.length; i++) {
intArray[i] = Integer.parseInt(stringsArray[i]);
}
now do any proses you want like print or sum or... on intArray
The whole code will be like this :
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String user_input = scan.nextLine();
String[] stringsArray = user_input.split(" ");
int[] intArray = new int[stringsArray.length];
for (int i = 0; i < stringsArray.length; i++) {
intArray[i] = Integer.parseInt(stringsArray[i]);
}
}
}

This works fine ....
int a = nextInt();
int b = nextInt();
int c = nextInt();
Or you can read them in a loop

Using this on many coding sites:
CASE 1: WHEN NUMBER OF INTEGERS IN EACH LINE IS GIVEN
Suppose you are given 3 test cases with each line of 4 integer inputs separated by spaces 1 2 3 4, 5 6 7 8 , 1 1 2 2
int t=3,i;
int a[]=new int[4];
Scanner scanner = new Scanner(System.in);
while(t>0)
{
for(i=0; i<4; i++){
a[i]=scanner.nextInt();
System.out.println(a[i]);
}
//USE THIS ARRAY A[] OF 4 Separated Integers Values for solving your problem
t--;
}
CASE 2: WHEN NUMBER OF INTEGERS in each line is NOT GIVEN
Scanner scanner = new Scanner(System.in);
String lines=scanner.nextLine();
String[] strs = lines.trim().split("\\s+");
Note that you need to trim() first: trim().split("\\s+") - otherwise, e.g. splitting a b c will emit two empty strings first
int n=strs.length; //Calculating length gives number of integers
int a[]=new int[n];
for (int i=0; i<n; i++)
{
a[i] = Integer.parseInt(strs[i]); //Converting String_Integer to Integer
System.out.println(a[i]);
}

created this code specially for the Hacker earth exam
Scanner values = new Scanner(System.in); //initialize scanner
int[] arr = new int[6]; //initialize array
for (int i = 0; i < arr.length; i++) {
arr[i] = (values.hasNext() == true ? values.nextInt():null);
// it will read the next input value
}
/* user enter = 1 2 3 4 5
arr[1]= 1
arr[2]= 2
and soo on
*/

It's working with this code:
Scanner input = new Scanner(System.in);
System.out.println("Enter Name : ");
String name = input.next().toString();
System.out.println("Enter Phone # : ");
String phone = input.next().toString();

A simple solution can be to consider the input as an array.
Scanner sc = new Scanner(System.in);
int n = sc.nextInt(); //declare number of integers you will take as input
int[] arr = new int[n]; //declare array
for(int i=0; i<arr.length; i++){
arr[i] = sc.nextInt(); //take values
}

You're probably looking for String.split(String regex). Use " " for your regex. This will give you an array of strings that you can parse individually into ints.

Better get the whole line as a string and then use StringTokenizer to get the numbers (using space as delimiter ) and then parse them as integers . This will work for n number of integers in a line .
Scanner sc = new Scanner(System.in);
List<Integer> l = new LinkedList<>(); // use linkedlist to save order of insertion
StringTokenizer st = new StringTokenizer(sc.nextLine(), " "); // whitespace is the delimiter to create tokens
while(st.hasMoreTokens()) // iterate until no more tokens
{
l.add(Integer.parseInt(st.nextToken())); // parse each token to integer and add to linkedlist
}

Using BufferedReader -
StringTokenizer st = new StringTokenizer(buf.readLine());
while(st.hasMoreTokens())
{
arr[i++] = Integer.parseInt(st.nextToken());
}

When we want to take Integer as inputs
For just 3 inputs as in your case:
import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int a,b,c;
a = scan.nextInt();
b = scan.nextInt();
c = scan.nextInt();
For more number of inputs we can use a loop:
import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int a[] = new int[n]; //where n is the number of inputs
for(int i=0;i<n;i++){
a[i] = scan.nextInt();
}

This method only requires users to enter the "return" key once after they have finished entering numbers:
It also skips special characters so that the final array will only contains integers
ArrayList<Integer> nums = new ArrayList<>();
// User input
Scanner sc = new Scanner(System.in);
String n = sc.nextLine();
if (!n.isEmpty()) {
String[] str = n.split(" ");
for (String s : str) {
try {
nums.add(Integer.valueOf(s));
} catch (NumberFormatException e) {
System.out.println(s + " cannot be converted to Integer, skipping...");
}
}
}

//Get user input as a 1 2 3 4 5 6 .... and then some of the even or odd number like as 2+4 = 6 for even number
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int evenSum = 0;
int oddSum = 0;
while (n > 0) {
int last = n % 10;
if (last % 2 == 0) {
evenSum += last;
} else {
oddSum += last;
}
n = n / 10;
}
System.out.println(evenSum + " " + oddSum);
}
}

if ur getting nzec error, try this:
try{
//your code
}
catch(Exception e){
return;
}

i know it's old discuss :) i tested below code it's worked
`String day = "";
day = sc.next();
days[i] = Integer.parseInt(day);`

How can I split a text using split by lines?

I am trying to split data by lines, using the method split. This is the code i am trying to use but i can't figure out what to use for the parameters of .split(). This is how the data will be in the txt.
19
23
58
49
Scanner sc = new Scanner(new File("random.txt"));
string line = sc.nextLine();
String[] numbers = line.split(" ");
int nums = new int[numbers.length];
for(int i=0;i<numbers.length;i++)
nums[i] = Integer.parseInt(numbers[i]);
The end goal is so that the data can be put into an array, not to just print it.

You dont need to use split if you have only one number in each line.
just use the following
Scanner sc = new Scanner(new File("C:/projects/random.txt"));
while( sc.hasNext()){
System.out.println(sc.nextInt());
}

Try to use it like this:
Scanner sc = new Scanner(new File("random.txt"));
int[] nums;
int i=0;
while(sc.hasNext()){
String line = sc.nextLine();
nums[i] = Integer.parseInt(line);
i++;
}
Hope this helps.

Just as simple as that, you don't need split since you're reading line by line as #Luiggi Mendoza said
Scanner sc = new Scanner(new File("C:/projects/random.txt"));
while( sc.hasNext()){
nums[i] = Integer.parseInt(numbers[i]); //They're stored in here
i++;
}
int max = i; //To keep length of numbers that have been read
for(i = 0; i < max; i++){
System.out.println(nums[i]); //We print them from the array
}

Try this
while(true){
int tmp=line.indexOf(" ");
if(tmp==-1)
break;
System.out.println(ar[i]);
ar[i++]=Integer.parseInt(line.substring(0,tmp));
line =line.substring(tmp+1);
}