This question already has answers here:
Recognizing text in a String Array
(3 answers)
Closed 7 years ago.
do{
input.nextLine();
linhas [nLinhas] = input.nextLine();
nLinhas++;
}
while ();
I have this inside a switch which is inside a do-while (menu). I am doing a text editor, in which I ask the user for input, and in this part I'm trying to store the input in "String [] linhas".
(Portuguese) | (English)
Linhas = Lines
nLinhas = Number of Lines
The two nextLine() is because of a previous next().charAt().
The program should keep asking for more input unless the user presses ENTER two times... How do I go about doing this? I've tried using .length, .contains, but nothing worked...
This works will take multiple "enter" keystrokes:
Scanner scanner = new Scanner(System.in);
String readString = scanner.nextLine();
while(readString!=null) {
System.out.println(readString);
if (readString.isEmpty()) {
System.out.println("Read Enter Key.");
}
if (scanner.hasNextLine()) {
readString = scanner.nextLine();
} else {
readString = null;
}
}
Have you tried adding a KeyListener and checking when the user hits Enter? Store a variable for space bar presses in a row, and if that number hits 2, perform an action.
Scanner scanner = new Scanner(System.in);
boolean hasNotEnd=true;
while(hasNotEnd) {
System.out.println("read 1st input0");
String readString1 = scanner.nextLine();
System.out.println("read 2nd input0");
String readString2 = scanner.nextLine();
if(readString1.isEmpty() && readString2.isEmpty()){
hasNotEnd=false;
}
This will be one solution
do {
String inputLine = input.nextLine();
linhas [nLinhas] = inputLine;
if (nLinhas > 1 && linhas[nLinhas].equals("") && linhas[nLinhas-1].equals("")) {
break;
}
nLinhas++;
}
while (true);
do{
String inputString;
inputString=input.nextLine();
linhas [nLinhas] = inputString;
if(nLinhas > 0 && linhas [nLinhas-1].equals("") && linhas [nLinhas].equals("")){
break;
}
nLinhas++;
}
while (true);
Related
How to take space separated input in Java using BufferedReader?
Please change the code accordingly, i wanted the values of a, b, n as space seperated integers and then I want to hit Enter after every test cases.
Which means first i'll input the number of test cases then i'll press the Enter key. Then i input the vale of a then i'll press Space, b then again Space then i'll input the value of n, then i'll press the Enter key for the input for the next testcase.
I know that this can be done easily through Scanner but i don't wanna use it because it throws TLE(Time Limit Extended) error on online judges.
public static void main(String[] args) throws IOException {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String inputString = br.readLine();
int testCases = Integer.parseInt(inputString);
double a,b,n,j,t=1;
int i;
int ans [] = new int[testCases];
for(i=0;i<testCases;i++)
{
inputString = br.readLine();
a = Double.parseDouble(inputString);
inputString = br.readLine();
b = Double.parseDouble(inputString);
inputString = br.readLine();
n = Double.parseDouble(inputString);
for(j=0;j<n;j++)
{
if(t==1)
{
a*=2;
t=0;
}
else if(t==0)
{
b*=2;
t=1;
}
}
if(a>b)
ans[i]=(int)(a/b);
else
ans[i]=(int)(b/a);
t=1;
}
for(i=0;i<testCases;i++)
System.out.println(ans[i]);
}catch(Exception e)
{
return;
}
}
First read the number of input lines to be read.
Then parse each line and get the String.
Though I have not added the NumberFormatException handling, but it's a good idea to have that.
Change your for loop like this:
for(i=0;i<testCases;i++){
inputString = br.readLine();
String input[] = inputString.split("\\s+");
a = Double.parseDouble(input[0]);
inputString = br.readLine();
b = Double.parseDouble(input[1]);
inputString = br.readLine();
n = Double.parseDouble(input[2]);
for(j=0;j<n;j++){
if(t==1){
a*=2;
t=0;
}else if(t==0){
b*=2;
t=1;
}
}
if(a>b){
ans[i]=(int)(a/b);
}else{
ans[i]=(int)(b/a);
t=1;
}
}
This question already has answers here:
How do I ensure that Scanner hasNextInt() asks for new input?
(2 answers)
Closed 6 years ago.
Desired outcome:
Accepts user input
Makes sure user inputs only 1 integer value at a time
Stores that integer in a variable
I tried to achieve this by doing the following:
Store user input in variable
Count number of tokens in variable
If there's not one token, reject the input
If the input is not of data type int, reject the input
Code:
Scanner scan = new Scanner(System.in);
System.out.println("Enter an integer:");
String myString = scan.nextLine();
int tokens = new StringTokenizer(myString, " ").countTokens();
while (tokens != 1 && !scan.hasNextInt()) {
System.out.println("Enter a single integer");
myString = scanner.nextLine();
tokens = new StringTokenizer(myString, " ").countTokens();
}
int number = scanner.nextInt();
System.out.println(number);
This code is full of holes. The output is inconsistent and undesired. It typically ends by throwing a java.util.InputMismatchException error, indicating the value it's trying to store isn't an int. I've experienced this error occur after one loop and after multiple loops, even with the same type and quantity of input (e.g. 2 strings).
Should I keep going with this code, or should I try to approach this problem from a different angle?
I've modified your program a little bit. My approach was to accept a single line of input. If the input contains more than one token, ask the user to re-enter input. If there is only one input, check if the input is an integer, if not, as the user to again provide input.
Seems to work for me:
Scanner scanner = new Scanner(System.in);
String myString;
int tokens;
int number;
do {
System.out.println("Enter a single integer");
myString = scanner.nextLine();
tokens = new StringTokenizer(myString, " ").countTokens();
try {
number = Integer.parseInt(myString);
} catch(NumberFormatException e) {
tokens = 0;
number = -1;
}
}while (tokens != 1);
scanner.close();
System.out.println(number);
Update: Alternate approach without using StringTokenizer
Scanner scanner = new Scanner(System.in);
String myString;
boolean validInput;
int number;
do {
System.out.println("Enter a single integer");
myString = scanner.nextLine();
try {
number = Integer.parseInt(myString);
validInput = true;
} catch(NumberFormatException e) {
validInput = false;
number = -1;
}
}while (validInput == false);
scanner.close();
System.out.println(number);
Update 2: Another approach using regular expressions to validate input before accepting it.
The Scanner allows us to use a regular expression to match the input. If the input matches the pattern, you can use it to accept the input. Otherwise, discard it and ask user to provide input again.
Here's the code:
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a single integer");
String integerPattern = "[+-]?\\d+$"; // positive or negative and digits only
while(scanner.hasNext(integerPattern) == false) {
String x = scanner.nextLine();// capture and discard input.
System.out.println("Enter a single integer. '" + x + "' is an invalid input.");
}
int number = scanner.nextInt(); // capture input only if it matches pattern.
scanner.close();
System.out.println("number: " + number);
Hope this helps!
First off, I am brand new to both Java and to this website. I am going to ask my question as thoroughly as I can. However, please let me know if you think I left something out.
I am working on a school assignment, and I am stuck on the second portion of it. I am able to prompt the user, but can not for the life of me, figure out how to ensure that the input string contains a comma. I did try searching this site, as well as Googling it, and haven't been able to find anything. Perhaps I am not wording the question appropriately.
(1) Prompt the user for a string that contains two strings separated by a comma.
(2) Report an error if the input string does not contain a comma. Continue to prompt until a valid string is entered. Note: If the input contains a comma, then assume that the input also contains two strings.
So far I have this:
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in); // Input stream for standard input
Scanner inSS = null; // Input string stream
String lineString = ""; // Holds line of text
String firstWord = ""; // First name
String secondWord = ""; // Last name
boolean inputDone = false; // Flag to indicate next iteration
// Prompt user for input
System.out.println("Enter string seperated by a comma: ");
// Grab data as long as "Exit" is not entered
while (!inputDone) {
// Entire line into lineString
lineString = scnr.nextLine();
// Create new input string stream
inSS = new Scanner(lineString);
// Now process the line
firstWord = inSS.next();
// Output parsed values
if (firstWord.equals("q")) {
System.out.println("Exiting.");
inputDone = true;
if else (lineString != ",") { // This is where I am stuck!
System.out.print("No comma in string");
}
} else {
secondWord = inSS.next();
System.out.println("First word: " + firstWord);
System.out.println("Second word: " + secondWord);
System.out.println();
}
}
return;
}
}
I know my "if else" is probably not correct. I just don't know where to begin for this particular command. Unfortunately my eBook chapter did not cover this specifically. Any thoughts would be greatly appreciated. Thank you so much!
I suspect you want to assert if the input contains a comma, and at least one letter either side. For this you need regex:
if (!input.matches("[a-zA-Z]+,[a-zA-Z]+")) {
System.out.print("Input not two comma separated words");
}
Since you are looking for a string with a comma in it and you want to get the string “Before” the comma and the string “After” the comma, then string.split(‘,’) is what you want. Asking if the string “Contains” a comma gives you no information about the string before or after the comma. That’s where string.split() helps. Since you don’t care “Where” the comma is you simply want the string before the comma and the string after the comma. The string.split(‘,’) method will return a string array containing the strings that are separated by commas (in your case) or any character.
Example:
string myString = “firstpart,secondpart”;
… then
string[] splitStringArray = myString.Split(‘,’)
This will return a string array of size 2 where
splitStringArray[0] = “firstpart”
splitStringArray[1] = “secondpart"
with this info you can also tell if the user entered the proper input… i.e…
if the splitStringArray.Length (or Size) = 0, then the user did not input anything, if the splitStringArray.Length (or Size) = 1 then the user input 1 string with no commas… might check for exit here. If the splitStringArray.Length (or Size) = 2 then the user input the string properly. if the splitStringArray.Length (Size) > 2 then the user input a string with more than 1 comma.
I hope that helps in describing how string.split works.
Your code however needs some work… without going into much detail below is a c# console while loop as an example:
inputDone = false;
while (!inputDone)
{
Console.Clear();
Console.WriteLine("Enter string seperated by a comma: ");
lineString = Console.ReadLine();
string[] splitStringArray = lineString.Split(',');
// check for user to quit
if (splitStringArray.Length == 1)
{
if (splitStringArray[0] == "q")
{
inputDone = true;
Console.Clear();
}
else
{
// 1 string that is not "q" with no commas
}
}
if (splitStringArray.Length == 2)
{
// then there are exactly two strings with a comma seperating them
// or you may have ",string" or "string,"
Console.WriteLine("First word: " + splitStringArray[0]);
Console.WriteLine("Second word: " + splitStringArray[1]);
Console.ReadKey();
}
else
{
Console.WriteLine("Input string empty or input string has more than two strings seperated by commas");
Console.ReadKey();
}
}
Hope that helps.
This worked for me:
import java.util.Scanner;
import java.io.IOException;
public class ParseStrings {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
Scanner inSS = null;
String lineString = "";
String firstWord = "";
String nextWord = "";
System.out.println("Enter input string: ");
while (lineString.matches("q") == false) {
lineString = scnr.nextLine();
lineString = lineString.replaceAll(",",", ");
inSS = new Scanner(lineString);
int delimComma = lineString.indexOf(",");
if ((delimComma <= -1) && (lineString.matches("q") == false)) {
System.out.println("Error: No comma in string");
System.out.println("Enter input string: ");
}
else if ((delimComma <= -1) && (lineString == null || lineString.length() == 0 || lineString.split("\\s+").length < 2) && (lineString.matches("q") == false)) {
System.out.println("Error: Two words");
System.out.println("Enter input string: ");
}
else if (lineString.matches("q") == false) {
firstWord = inSS.next();
nextWord = inSS.nextLine();
System.out.println("First word: " + firstWord.replaceAll("\\s","").replaceAll("\\W","").replaceAll("\\n",""));
System.out.println("Second word: " + nextWord.replaceAll("\\s","").replaceAll("\\W","").replaceAll("\\n",""));
System.out.println("\n");
System.out.println("Enter input string: ");
}
continue;
}
return;
}
}
I have tried using Scanner to read from console into a string object and keep adding the data until the user pushes enter twice .How can I improve my code?
String text;
public void Settext() {
System.out.println("please enter the values for the text :");
String S;
Scanner scn = new Scanner(System.in);
if ((S = scn.next())!= null) {
text += S.split("\\|");
}
scn.close();
}
public String toString() {
Settext();
String S = "the output of document class toString method is " + text;
return S;
}
Use this instead of your if statement -
int noOfNulls = 0;
while(noOfNulls != 2)
{
if ((S = scn.next()) != null)
{
text += S.split("\\|");
noOfNulls = 0;
}
else
noOfNulls++;
}
I think this might help you. Does what you describe. Taking in consideration that a user might press Enter Key several times but no consecutively.
Scanner scanner = new Scanner(System.in);
String readString = scanner.nextLine();
String buffer="";
boolean previusEnter=false;
while(readString!=null) {
if (readString.equals("")){
if(previusEnter)
break;
previusEnter=true;
}
else
previusEnter=false;
buffer+= readString+"\n";
if (scanner.hasNextLine())
readString = scanner.nextLine();
else
readString = null;
}
I am using java and I have a code as follow:
Scanner scanner = new Scanner(System.in);
while (true) {
String token = scanner.next();
if (token.equals("$")) break;
if (token.equals("(")) do sth;
else if (token.equals(")")) do sth;
else {
do sth
}
}
as you can see in the above code if you enter sth in the console then you enter $ at the end then the program will understand the end of input and the scanner can succesfully get each word of the string succesfully but instead I want when the user push enter then the scanner grabs the whole string and start reading it word by word I tried it this way :
Scanner scanner = new Scanner(System.in);
while (scanner.hasNext()) {
String token = scanner.next();
if (token.equals("(")) builder.buildOpenBracket();
else if (token.equals(")")) builder.buildCloseBracket();
else {
int number = Integer.parseInt(token);
builder.buildElement(number);
}
}
but now the proram runs forever and nothing happends
Firstly, to read new line and save it in a String you should use .nextLine()
Anyway I fixed it this way:
Scanner scanner = new Scanner(System.in);
String token = scanner.nextLine();
Scanner scannerToken = new Scanner(token);
while (scannerToken.hasNext()) {
String statement = scannerToken.next();
if (statement.equals("("))
else if (statement.equals(")"))
else {
}
}