Instead of having to press Enter after each value input with Scanner, is there a way to type all values at once, and then press enter and be done?
import java.util.Arrays;
import java.util.Scanner;
class Arrayex {
public static void main(String[] args)
{
int [] numbers = new int[5];
Scanner s=new Scanner(System.in);
System.out.println("Current array: " + Arrays.toString(numbers));
System.out.println("Type in the numbers: ");
for(int i=0; i< numbers.length; i++)
{
numbers[i] = s.nextInt();
}
System.out.println("Array elements are: " + Arrays.toString(numbers));
}
}
Current array input by pressing Enter after every number
How I want to type in the numbers into the array
My friend told me I can use a String array and convert it to int array and type the string as "1,2,3,4,5".
Wouldn't this only use up the location at numbers[0] instead of numbers[0] to numbers[5]?
Enter all int elements in one line using space, it will use as separate int values.
it will look like this.
No need to take input as String and parse it to an integer.
(White)space as delimiter
As others have noted, if you just use space as separator, then you could leverage the Scanner to convert the input to ints. The input 2 3 5 7 11 will yield an int[] with the given integers als elements.
Comma as delimiter
If you want to use comma as delimiter instead, the current code won't work. The input 2,3,5,7,11 will indeed try to shove 2,3,5,7,11 into numbers[0], which obviously will fail, and an InputMismatchException will be thrown at you.
Instead, you could set the delimiter:
Scanner s = new Scanner(System.in);
s.useDelimiter("[,\n]")
This will cause the Scanner to process the tokens between each comma or newline as separate elements.
Note that we couldn't just use , alone, because then the Scanner keeps reading from System.in indefinitely.
System.out.println("Number of pages + Number of lost pages + Number of Readers");
int n = s.nextInt();
int m = s.nextInt();
int q = s.nextInt();
I want to read input values all the values are going to be integer but I want to read it in a same line with changing it form Integer.
Assuming s is an instance of Scanner: Your code, as written, does exactly what you want.
scanners are created by default with a delimiter configured to be 'any whitespace'. nextInt() reads the next token (which are the things in between the delimiter, i.e. the whitespace), and returns it to you by parsing it into an integer.
Thus, your code as pasted works fine.
If it doesn't, stop setting up a delimiter, or reset it back to 'any whitespace' with e.g. scanner.reset(); or scanner.useDelimiter("\\s+");.
class Example {
public static void main(String[] args) {
var in = new Scanner(System.in);
System.out.println("Enter something:");
System.out.println(in.nextInt());
System.out.println(in.nextInt());
System.out.println(in.nextInt());
}
}
works fine here.
I'm doing a project for a Uni course where I need to read an input of an int followed by a '+' in the form of (for example) "2+".
However when using nextInt() it throws an InputMismatchException
What are the workarounds for this as I only want to store the int, but the "user", inputs an int followed by the char '+'?
I've already tried a lot of stuff including parseInt and valueOf but none seemed to work.
Should I just do it manually and analyze char by char?
Thanks in advance for your help.
Edit: just to clear it up. All the user will input is and Int followed by a + after. The theme of the project is to do something in the theme of a Netflix program. This parameter will be used as the age rating for a movie. However, I don't want to store the entire string in the movie as it would make things harder to check if a user is eligible or not to watch a certain movie.
UPDATE: Managed to make the substring into parseInt to work
String x = in.nextLine();
x = x.substring(0, x.length()-1);
int i = Integer.parseInt(x);
Thanks for your help :)
Try out Scanner#useDelimiter():
try(Scanner sc=new Scanner(System.in)){
sc.useDelimiter("\\D"); /* use non-digit as separator */
while(sc.hasNextInt()){
System.out.println(sc.nextInt());
}
}
Input: 2+33-599
Output:
2
33
599
OR with your current code x = x.substring(0, x.length()-1); to make it more precise try instead: x = x.replaceAll("\\D","");
Yes you should manually do it. The methods that are there will throw a parse exception. Also do you want to remove all non digit characters or just plus signs? For example if someone inputs "2 plus 5 equals 7" do you want to get 257 or throw an error? You should define strict rules.
You can do something like: Integer.parseInt(stringValue.replaceAll("[^\d]","")); to remove all characters that are no digits.
Hard way is the only way!
from my Git repo line 290.
Also useful Javadoc RegEx
It takes in an input String and extracts all numbers from it then you tokenize the string with .replaceAll() and read the tokens.
int inputLimit = 1;
Scanner scan = new Scanner(System.in);
try{
userInput = scan.nextLine();
tokens = userInput.replaceAll("[^0-9]", "");
//get integers from String input
if(!tokens.equals("")){
for(int i = 0; i < tokens.length() && i < inputLimit; ++i){
String token = "" + tokens.charAt(i);
int index = Integer.parseInt(token);
if(0 == index){
return;
}
cardIndexes.add(index);
}
}else{
System.out.println("Please enter integers 0 to 9.");
System.out.print(">");
}
Possible solutions already have been given, Here is one more.
Scanner sc = new Scanner(System.in);
String numberWithPlusSign = sc.next();
String onlyNumber = numberWithPlusSign.substring(0, numberWithPlusSign.indexOf('+'));
int number = Integer.parseInt(onlyNumber);
I am trying to find a way to take a char input from the keyboard.
I tried using:
Scanner reader = new Scanner(System.in);
char c = reader.nextChar();
This method doesn't exist.
I tried taking c as a String. Yet, it would not always work in every case, since the other method I am calling from my method requires a char as an input. Therefore I have to find a way to explicitly take a char as an input.
Any help?
You could take the first character from Scanner.next:
char c = reader.next().charAt(0);
To consume exactly one character you could use:
char c = reader.findInLine(".").charAt(0);
To consume strictly one character you could use:
char c = reader.next(".").charAt(0);
Setup scanner:
reader.useDelimiter("");
After this reader.next() will return a single-character string.
There is no API method to get a character from the Scanner. You should get the String using scanner.next() and invoke String.charAt(0) method on the returned String.
Scanner reader = new Scanner(System.in);
char c = reader.next().charAt(0);
Just to be safe with whitespaces you could also first call trim() on the string to remove any whitespaces.
Scanner reader = new Scanner(System.in);
char c = reader.next().trim().charAt(0);
There are three ways to approach this problem:
Call next() on the Scanner, and extract the first character of the String (e.g. charAt(0)) If you want to read the rest of the line as characters, iterate over the remaining characters in the String. Other answers have this code.
Use setDelimiter("") to set the delimiter to an empty string. This will cause next() to tokenize into strings that are exactly one character long. So then you can repeatedly call next().charAt(0) to iterate the characters. You can then set the delimiter to its original value and resume scanning in the normal way!
Use the Reader API instead of the Scanner API. The Reader.read() method delivers a single character read from the input stream. For example:
Reader reader = new InputStreamReader(System.in);
int ch = reader.read();
if (ch != -1) { // check for EOF
// we have a character ...
}
When you read from the console via System.in, the input is typically buffered by the operating system, and only "released" to the application when the user types ENTER. So if you intend your application to respond to individual keyboard strokes, this is not going to work. You would need to do some OS-specific native code stuff to turn off or work around line-buffering for console at the OS level.
Reference:
How to read a single char from the console in Java (as the user types it)?
You can solve this problem, of "grabbing keyboard input one char at a time" very simply. Without having to use a Scanner all and also not clearing the input buffer as a side effect, by using this.
char c = (char)System.in.read();
If all you need is the same functionality as the C language "getChar()" function then this will work great. The Big advantage of the "System.in.read()" is the buffer is not cleared out after each char your grab. So if you still need all the users input you can still get the rest of it from the input buffer. The "char c = scanner.next().charAt(0);" way does grab the char but will clear the buffer.
// Java program to read character without using Scanner
public class Main
{
public static void main(String[] args)
{
try {
String input = "";
// Grab the First char, also wait for user input if the buffer is empty.
// Think of it as working just like getChar() does in C.
char c = (char)System.in.read();
while(c != '\n') {
//<do your magic you need to do with the char here>
input += c; // <my simple magic>
//then grab the next char
c = (char)System.in.read();
}
//print back out all the users input
System.out.println(input);
} catch (Exception e){
System.out.println(e);
}
}
}
Hope this helpful, and good luck! P.S. Sorry i know this is an older post, but i hope that my answer bring new insight and could might help other people who also have this problem.
This actually doesn't work:
char c = reader.next().charAt(0);
There are some good explanations and references in this question:
Why doesn't the Scanner class have a nextChar method?
"A Scanner breaks its input into tokens using a delimiter pattern", which is pretty open ended. For example when using this
c = lineScanner.next().charAt(0);
for this line of input
"(1 + 9) / (3 - 1) + 6 - 2"
the call to next returns "(1", c will be set to '(', and you'll end up losing the '1' on the next call to next()
Typically when you want to get a character you would like to ignore whitespace. This worked for me:
c = lineScanner.findInLine("[^\\s]").charAt(0);
Reference:
regex to match a single character that is anything but a space
The best way to take input of a character in Scanner class is:
Scanner sca=new Scanner(System.in);
System.out.println("enter a character");
char ch=sca.next().charAt(0);
You should use your custom input reader for faster results instead of extracting first character from reading String.
Link for Custom ScanReader and explanation: https://gist.github.com/nik1010/5a90fa43399c539bb817069a14c3c5a8
Code for scanning Char :
BufferedInputStream br=new BufferedInputStream(System.in);
char a= (char)br.read();
There are two approaches, you can either take exactly one character or strictly one character.
When you use exactly, the reader will take only the first character, irrespective of how many characters you input.
For example:
import java.util.Scanner;
public class ReaderExample {
public static void main(String[] args) {
try {
Scanner reader = new Scanner(System.in);
char c = reader.findInLine(".").charAt(0);
reader.close();
System.out.print(c);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
When you give a set of characters as input, say "abcd", the reader will consider only the first character i.e., the letter 'a'
But when you use strictly, the input should be just one character. If the input is more than one character, then the reader will not take the input
import java.util.Scanner;
public class ReaderExample {
public static void main(String[] args) {
try {
Scanner reader = new Scanner(System.in);
char c = reader.next(".").charAt(0);
reader.close();
System.out.print(c);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
Suppose you give input "abcd", no input is taken, and the variable c will have Null value.
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
char c = reader.next(".").charAt(0);
}
}
To get only one character char c = reader.next(".").charAt(0);
import java.util.Scanner;
public class userInput{
public static void main(String[] args){
// Creating your scanner with name kb as for keyBoard
Scanner kb = new Scanner(System.in);
String name;
int age;
char bloodGroup;
float height;
// Accepting Inputs from user
System.out.println("Enter Your Name");
name = kb.nextLine(); // for entire line of String including spaces
System.out.println("Enter Your Age");
age = kb.nextInt(); // for taking Int
System.out.println("Enter Your BloodGroup : A/B/O only");
bloodGroup = kb.next().charAt(0); // For character at position 0
System.out.println("Enter Your Height in Meters");
height = kb.nextFloat(); // for taking Float value
// closing your scanner object
kb.close();
// Outputting All
System.out.println("Name : " +name);
System.out.println("Age : " +age);
System.out.println("BloodGroup : " +bloodGroup);
System.out.println("Height : " +height+" m");
}
}
Try this:
char c=S.nextLine().charAt(0);
// Use a BufferedReader to read characters from the console.
import java.io.*;
class BRRead {
public static void main(String args[]) throws IOException
{
char c;
BufferedReader br = new
BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter characters, 'q' to quit.");
// read characters
do {
c = (char) br.read();
System.out.println(c);
} while(c != 'q');
}
}
You should get the String using scanner.next() and invoke String.charAt(0) method on the returned String.
Exmple :
import java.util.Scanner;
public class InputC{
public static void main(String[] args) {
// TODO Auto-generated method stub
// Declare the object and initialize with
// predefined standard input object
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a character: ");
// Character input
char c = scanner.next().charAt(0);
// Print the read value
System.out.println("You have entered: "+c);
}
}
output
Enter a character:
a
You have entered: a
you just need to write this for getting value in char type.
char c = reader.next().charAt(0);
try followings.
Scanner reader = new Scanner(System.in);
char c = reader.next().charAt(0);
this will get a character from the keyboard.
import java.io.*;
class abc // enter class name (here abc is class name)
{
public static void main(String arg[])
throws IOException // can also use Exception
{
BufferedReader z =
new BufferedReader(new InputStreamReader(System.in));
char ch = (char) z.read();
} // PSVM
} // class
Try this
Scanner scanner=new Scanner(System.in);
String s=scanner.next();
char c=s.charAt(0);
Scanner key = new Scanner(System.in);
//shortcut way
char firstChar=key.next().charAt(0);
//how it works;
/*key.next() takes a String as input then,
charAt method is applied on that input (String)
with a parameter of type int (position) that you give to get
that char at that position.
You can simply read it out as:
the char at position/index 0 from the input String
(through the Scanner object key) is stored in var. firstChar (type char) */
//you can also do it in a bit elabortive manner to understand how it exactly works
String input=key.next(); // you can also write key.nextLine to take a String with spaces also
char firstChar=input.charAt(0);
char charAtAnyPos= input.charAt(pos); // in pos you enter that index from where you want to get the char from
By the way, you can't take a char directly as an input. As you can see above, a String is first taken then the charAt(0); is found and stored
Simple solution to read a charachter from user input.
Read a String. Then use charAt(0) over String
Scanner reader = new Scanner(System.in);
String str = reader.next();
char c = str.charAt(0);
That's it.
You could use typecasting:
Scanner sc= new Scanner(System.in);
char a=(char) sc.next();
This way you will take input in String due to the function 'next()' but then it will be converted into character due to the 'char' mentioned in the brackets.
This method of conversion of data type by mentioning the destination data type in brackets is called typecating. It works for me, I hope it works for u :)
Just use...
Scanner keyboard = new Scanner(System.in);
char c = keyboard.next().charAt(0);
This gets the first character of the next input.
To find the index of a character in a given sting, you can use this code:
package stringmethodindexof;
import java.util.Scanner;
import javax.swing.JOptionPane;
/**
*
* #author ASUS//VERY VERY IMPORTANT
*/
public class StringMethodIndexOf {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
String email;
String any;
//char any;
//any=JOptionPane.showInputDialog(null,"Enter any character or string to find out its INDEX NUMBER").charAt(0);
//THE AVOBE LINE IS FOR CHARACTER INPUT LOL
//System.out.println("Enter any character or string to find out its INDEX NUMBER");
//Scanner r=new Scanner(System.in);
// any=r.nextChar();
email = JOptionPane.showInputDialog(null,"Enter any string or anything you want:");
any=JOptionPane.showInputDialog(null,"Enter any character or string to find out its INDEX NUMBER");
int result;
result=email.indexOf(any);
JOptionPane.showMessageDialog(null, result);
}
}
The easiest way is, first change the variable to a String and accept the input as a string. Then you can control based on the input variable with an if-else or switch statement as follows.
Scanner reader = new Scanner(System.in);
String c = reader.nextLine();
switch (c) {
case "a":
<your code here>
break;
case "b":
<your code here>
break;
default:
<your code here>
}
I'm really new to java and i'm taking an introductory class to computer science. I need to know how to Prompt the user to user for two values, declare and define 2 variables to store the integers, and then be able to read the values in, and finally print the values out. But im pretty lost and i dont even know how to start i spent a whole day trying.. I really need some help/guidance. I need to do that for integers, decimal numbers and strings. Can someone help me?
You can do this by using Scanner class :
A simple text scanner which can parse primitive types and strings using regular expressions.
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.
For example, this code allows a user to read a number from System.in:
Scanner scan = new Scanner(System.in);
int i = scan.nextInt();
int j = scan.nextInt();
System.out.println("i = "+i +" j = "+j);
nextInt() : -Scans the next token of the input as an int and returns the int scanned from the input.
For more.
or to get user input you can also use the Console class : provides methods to access the character-based console device, if any, associated with the current Java virtual machine.
Console console = System.console();
String s = console.readLine();
int i = Integer.parseInt(console.readLine());
or you can also use BufferedReader and InputStreamReader classes and
DataInputStream class to get user input .
Use the Scanner class to get the values from the user. For integers you should use int, for decimal numbers (also called real numbers) use double and for strings use Strings.
A little example:
Scanner scan = new Scanner(System.in);
int intValue;
double decimalValue;
String textValue;
System.out.println("Please enter an integer value");
intValue = scan.nextInt(); // see how I use nextInt() for integers
System.out.println("Please enter a real number");
decimalValue = scan.nextDouble(); // nextDouble() for real numbers
System.out.println("Please enter a string value");
textValue = scan.next(); // next() for string variables
System.out.println("Your integer is: " + intValue + ", your real number is: "
+ decimalValue + " and your string is: " + textValue);
If you still don't understand something, please look further into the Scanner class via google.
As you will likely continue to run into problems like this in your class and in your programming career:
Lessons on fishing.
Learn to explore the provided tutorials through oracle.
Learn to read the Java API documentation
Now to the fish.
You can use the Scanner class. Example provided in the documentation.
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();