Develop Reference

How do I process different delimiters in a RegEx expression with Java?

I am working on creating a program for my course, in which I am required to divide the string: This;is;the;first;line;;This;is;the;second;line!;;;;Done!;;.
In the requirements, I need to read a single semicolon as a space, and a double semicolon as a new line. How do I create a regular expression in the useDelimiter() method that allows me to parse through and differentiate between both ; and ;;? Thank you!
Assignment Excerpt:
Instead of hard-coding the string, this time you will read it from the console. Study the useDelimiter() method and use it to set the delimiter for the scanner input. This time allow either colons or semicolons as the delimiters. One might prefer to use the String Tokenizer here, but don’t -- use the Scanner’s useDelimiter() method to set the delimiter in the Scanner and process each token as it comes.
import java.util.Scanner;
public class Hw3p2 {
public static void main(String[] args) {
// Initializes scanner class.
Scanner input = new Scanner(System.in);
// Prompts user for input.
System.out.println("Enter the string you wish to filter & parse: ");
// Reads user input.
String filterString = input.nextLine();
// Initiates new scanner reading the user inputted string.
Scanner a = new Scanner(filterString);
a.useDelimiter(";|;;");
System.out.printf("\n");
// Loop that parses through string while there are more tokens.
while(a.hasNext()) {
System.out.print(a.next());
}
}
}
The Expected output is to be:

You may use this code:
public class Hw3p2 {
public static void main(String[] args) {
// Initializes scanner class.
Scanner input = new Scanner(System.in).useDelimiter(";;");
// Prompts user for input.
System.out.print("Enter the string you wish to filter & parse: ");
// Reads user input.
while(input.hasNext()) {
String filterString = input.next();
//System.err.println("filterString: " + filterString);
// Initiates new scanner reading the user inputted string.
Scanner a = new Scanner(filterString).useDelimiter(";");
// Loop that parses through string while there are more tokens.
while(a.hasNext()) {
System.out.print(a.next() + " ");
}
System.out.println();
a.close();
}
input.close();
}
}
Output:
Enter the string you wish to filter & parse: This;is;the;first;line;;This;is;the;second;line!;;;;Done!;;
This is the first line
This is the second line!
Done!
Note use of outer scanner with delimiter ;; and an inner one with ;.

Is there a way to accept a single character as an input?

New to programming, so my apologies if this is dumb question.
When utilizing the Scanner class, I fail to see if there is an option for obtaining a single character as input. For example,
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String a = input.nextLine();
}
}
The above code allows me to pull the next line into a string, which can then be validated by using a while or if statement using a.length() != 1 and then stored into a character if needed.
But is there a way to pull a single character instead of utilizing a string and then validating? If not, can someone explain why this is not allowed? I think it may be due to classes or objects vs primitive types, but am unsure.

You can use System.in.read() instead of Scanner
char input = (char) System.in.read();
You can also use Scanner, doing something like:
Scanner scanner = new Scanner(System.in);
char input = scanner.next().charAt(0);
For using Stringinstead of char, you can also to convert to String:
Scanner scanner = new Scanner(System.in);
String input = String.valueOf(input.next().charAt(0));
This is less fancy than other ways, but for a newbie, it'll be easier to understand. On the other hand, I think the problem proposed doesn't need amazing performance.

Set the delimiter so every character is a token:
Scanner input = new Scanner(System.in).useDelimiter("(?<=.)");
String c = input.next(); // one char
The regex (?<=.) is a look behind, which has zero width, that matches after every character.

Uppercase a string input from scanner in java

I am supposed to use the Scanner in Java to receive a 14 char input and have all the letter char output in uppercase format. I've tried entering some of the code I found through Google such as " str.toUpperCase(Locale.ENGLISH); " but it tells me str cannot be resolved and that the locale can't be resolved. When I did a search on here I got results for uppercasing specific char or counting char. I just need the specific line of input to be uppercased.
The following is what I have at the moment. I am using eclipse java neon
import java.util.Scanner;
public class MemberIDLotz {
// Everette Lotz
public static void main(String[] args) {
Scanner string = new Scanner(System.in);
// We're going to get a 14 char string from a user.
System.out.println("Please enter in a 14 character long ID");
String name = string.next();
str.toUpperCase(Locale.ENGLISH);
string.close();
}
}
Thank you for your help in advance.
*Edit: Ok so it is no longer giving me an error message, and yes I had simply copy and pasted the code. However when it prints out its not in upper case format. I put the following right after "String name =...." and deleted the str.toUppercase() line:
System.out.println(name);
name = name.toUpperCase();`

Is there a reason you don't uppercase immediately?
String name = string.next().toUpperCase()

Change to
name = name.toUpperCase(Locale.ENGLISH);
or more simply
name = name.toUpperCase();

You can also add trim to it if you'd like, it is a working example:
String choice;
Scanner s = new Scanner(System.in);
choice = s.nextLine().trim().toUpperCase();

How do I make Java register a string input with spaces?

Here is my code:
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String question;
question = in.next();
if (question.equalsIgnoreCase("howdoyoulikeschool?") )
/* it seems strings do not allow for spaces */
System.out.println("CLOSED!!");
else
System.out.println("Que?");
When I try to write "how do you like school?" the answer is always "Que?" but it works fine as "howdoyoulikeschool?"
Should I define the input as something other than String?

in.next() will return space-delimited strings. Use in.nextLine() if you want to read the whole line. After reading the string, use question = question.replaceAll("\\s","") to remove spaces.

Since it's a long time and people keep suggesting to use Scanner#nextLine(), there's another chance that Scanner can take spaces included in input.
Class Scanner
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace.
You can use Scanner#useDelimiter() to change the delimiter of Scanner to another pattern such as a line feed or something else.
Scanner in = new Scanner(System.in);
in.useDelimiter("\n"); // use LF as the delimiter
String question;
System.out.println("Please input question:");
question = in.next();
// TODO do something with your input such as removing spaces...
if (question.equalsIgnoreCase("howdoyoulikeschool?") )
/* it seems strings do not allow for spaces */
System.out.println("CLOSED!!");
else
System.out.println("Que?");

I found a very weird thing in Java today, so it goes like -
If you are inputting more than 1 thing from the user, say
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();
double d = sc.nextDouble();
String s = sc.nextLine();
System.out.println(i);
System.out.println(d);
System.out.println(s);
So, it might look like if we run this program, it will ask for these 3 inputs and say our input values are 10, 2.5, "Welcome to java"
The program should print these 3 values as it is, as we have used nextLine() so it shouldn't ignore the text after spaces that we have entered in our variable s
But, the output that you will get is -
10
2.5
And that's it, it doesn't even prompt for the String input.
Now I was reading about it and to be very honest there are still some gaps in my understanding, all I could figure out was after taking the int input and then the double input when we press enter, it considers that as the prompt and ignores the nextLine().
So changing my code to something like this -
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();
double d = sc.nextDouble();
sc.nextLine();
String s = sc.nextLine();
System.out.println(i);
System.out.println(d);
System.out.println(s);
does the job perfectly, so it is related to something like "\n" being stored in the keyboard buffer in the previous example which we can bypass using this.
Please if anybody knows help me with an explanation for this.

Instead of
Scanner in = new Scanner(System.in);
String question;
question = in.next();
Type in
Scanner in = new Scanner(System.in);
String question;
question = in.nextLine();
This should be able to take spaces as input.

This is a sample implementation of taking input in java, I added some fault tolerance on just the salary field to show how it's done. If you notice, you also have to close the input stream .. Enjoy :-)
/* AUTHOR: MIKEQ
* DATE: 04/29/2016
* DESCRIPTION: Take input with Java using Scanner Class, Wow, stunningly fun. :-)
* Added example of error check on salary input.
* TESTED: Eclipse Java EE IDE for Web Developers. Version: Mars.2 Release (4.5.2)
*/
import java.util.Scanner;
public class userInputVersion1 {
public static void main(String[] args) {
System.out.println("** Taking in User input **");
Scanner input = new Scanner(System.in);
System.out.println("Please enter your name : ");
String s = input.nextLine(); // getting a String value (full line)
//String s = input.next(); // getting a String value (issues with spaces in line)
System.out.println("Please enter your age : ");
int i = input.nextInt(); // getting an integer
// version with Fault Tolerance:
System.out.println("Please enter your salary : ");
while (!input.hasNextDouble())
{
System.out.println("Invalid input\n Type the double-type number:");
input.next();
}
double d = input.nextDouble(); // need to check the data type?
System.out.printf("\nName %s" +
"\nAge: %d" +
"\nSalary: %f\n", s, i, d);
// close the scanner
System.out.println("Closing Scanner...");
input.close();
System.out.println("Scanner Closed.");
}
}

copyValueOf in Java?

import java.util.Scanner;
public class CourseSplitter {
public static void main(String args[]){
Scanner keyboard = new Scanner(System.in);
char[] course; //course code format: ABCDE##
String code;
//int num;
System.out.println("Input Course: ");
course = keyboard.next();
System.out.println(course);
code = String.copyValueOf(course, 0, 4);
System.out.println(code);
}
}
I don't know how I should let the user input the course when I'm using a character array instead of string. In short, how do I use the "scanner" on character arrays?
The instruction is the user will input a course code in the format: ABCDE##
Then, the program must split it into the course name and the course number. So, I had to use the copyValueOf method but it doesn't seem to work because from all the articles I read online, they used a char[] array but initialized the array with some value. So I was wondering how I could use the scanner on character arrays.

Why not just read a string from the scanner and then call String.toCharArray? It's not even clear why you need a char array here...

Why not just read a string directly with scanner.nextLine?
import java.util.Scanner;
public class CourseSplitter {
public static void main(String args[]){
Scanner keyboard = new Scanner(System.in);
System.out.println("Input Course: ");
String course = keyboard.nextLine();
System.out.println(course);
String code = course.substring(0, 5); //You put 4 but it left out the last letter in the course name. I changed it to 5 and it worked but I'm confused since the index always start with 0.
System.out.println(code);
String num = course.substring(5, 6);
System.out.println(num);
}
}