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Parse a string and cast certain elements to int

I was working on a bit of code where you would take an input of 2 numbers, separated by a comma, and then would proceed to do other actions with the numbers.
I was wondering how I would parse the string to take the first number up to the comma, cast it to and int and then proceed to cast the second number to an int.
Here is the code I was working on:
Scanner Scan = new Scanner(System.in);
System.out.print("Enter 2 numbers (num1,num2): ");
//get input
String input = Scan.nextLine();
//parse string up to comma, then cast to an integer
int firstNum = Integer.parseInt(input.substring(0, input.indexOf(',')));
int secondNum = Integer.parseInt(Scan.nextLine());
Scan.close();
System.out.println(firstNum + "\n" + secondNum);
The first number is cast to an integer just fine, I run into issues with the second one.
Exception in thread "main" java.lang.NumberFormatException: For input string: ""
How would I be able to then take the second integer out of the input string and cast it to an Int.

The error mode you're encountering seems reasonable indeed, as you're reading the next line from the scanner and therefore explicitly no longer operating on the first input anymore.
What you're looking for is probably this:
int secondNum = Integer.parseInt(input.substring(input.indexOf(',') + 1));

When defining secondNum, you're setting it equal to the parsed integer of the next line the scanner object reads, but all of the data has already been read. So rather than read from the scanner again, you'll want to call Integer.parseInt on everything after the comma.

It fails because all digit are given by the user on the same line. and you have two Scanner.nextLine(); the second is probably empty.
here is a solution :
Scanner Scan = new Scanner(System.in);
System.out.print("Enter 2 numbers (num1,num2): ");
//get input
String input = Scan.nextLine();
StringTokenizer st = new StringTokenizer(input, ",");
List<Integer> numbers = new ArrayList<>();
while (st.hasMoreElements()) {
numbers.add(Integer.parseInt(st.nextElement()));
}
System.out.println(numbers);

If input on one line, both the numbers will be stored in the String variable input. You don't need to scan another line. It will be empty, and you cannot cast the empty string to an int. Why not just parse the second number out of input, as you did the first.

How to print a string with an int

I am trying to get this code to run and basically solve an equation. So, I asked the user to write an equation. It looked like this:
System.out.println("Write an equation and I will solve for x.");
int answer = in.nextLine();
But I can't get the user to write a string and an int. Do I need to say String answer or int answer?

An int is used when you want the user to enter a number, but here you're looking for a combination of numbers and other characters, so you will need to use a string. When you have the equation stored in a string, you can use other methods to split up the equation into something solvable, then set int answer to whatever the answer comes out to be.

On a simpler side, String will be required input from the user, User will enter the equation.
Then comes the complex part of solving/computing the equation.
1.) create your own parser to pass operands/operator.
2.) Provide a equation with values to some API, you can make use of MVEL or ANTLR

Here's a little program that demonstrates one way to get the equation and divide into numeric / non-numeric values provided the equation input is space delimited. You can then determine what the non-numeric values are and proceed from there.
import java.util.Scanner;
public class SolveX{
public static void main(String[] a){
Scanner in = new Scanner(System.in);
System.out.println("Write an equation and I will solve for x.");
String input = "";
while( in.hasNext() ){
input = in.next();
try{
double d = Double.parseDouble(input);
System.out.println("Double found at: " + input);
// Do what you need to with the numeric value
}
catch(NumberFormatException nfe){
System.out.println("No double found at: " + input);
// Do what you need to with the non numeric value
}
}
}//end main
}//end SolveX class

Validation input to be string only and numbers only JAVA [duplicate]

This question already has answers here:
How to check if a String is numeric in Java
(41 answers)
Closed 8 years ago.
I am a student and i have a little problem with validation inputs.
String name;
System.out.println("Enter name:");
name = keyboard.nextLine();
//If name contain other than alphabetical character print an error
double number;
System.out.println("Enter number:");
name = keyboard.nextDouble();
//If number contain other than number print an error
What i have tried is test to parse the string to double but i could not.
I have no idea how to test if the double is only number.
Please give me a clue of what i should do.

You can use Regular expression to check if the input match your constraint as follow :
String name;
System.out.println("Enter name:");
name = keyboard.nextLine();
if (!name.matches("[a-zA-Z_]+")) {
System.out.println("Invalid name");
}
String number;
System.out.println("Enter number:");
number = keyboard.nextLine();
if (!number.matches("[0-9]+")) {
System.out.println("Invalid number");
}
Here is a good tutorial to learn regex .

You can loop through each character of the String and check if it's not alphabetic using Character.isAlphabetic(char):
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter name:");
String name = keyboard.nextLine();
for (char c : name.toCharArray()) {
if (!Character.isAlphabetic(c)){
System.out.println("INVALID");
break;
}
}
To only accept numbers, you can do something similar using the Character.isDigit(char) function, but note that you will have to read the input as a String not a double, or get the input as a double and the converting it to String using Double.toString(d).

double number = 0;
try {
number = Double.parseDouble(name)
} catch (NumberFormatException ex) {
System.out.println("Name is not a double.");
}
If number is not a double, you can catch a NumberFormatException.

It seems you are using scanner. If you are, you can use the Scanner class' hasNextDouble() to check if the input is a double before reading the double as shown below:
double number;
System.out.println("Enter number:");
if (keyboard.hasNextDouble()){
name = keyboard.nextDouble();
}
Have a look at the Scanner class docs for more information.

There is also the "fancier" regex solution.
Java Pattern Documentation
You can use this (untested code) given you used nextLine() for reading BOTH inputs:
boolean isWordOnly = Pattern.matches("\w*", name); //name is in your code
boolean isFloatOnly = Pattern.matches("\d*.?\d*", number); //number is in your code too
Now the too boolean values tell you if there is the desired format in your input. You can add it in a do - while loop or anything you want.
It is a good idea to start studying reg(ular) ex(presions) because they are useful in string formatting (Imagine that you have to test if the input is a valid email...). Also used to check for SQL injections and many key things in apps and programs generally.

How to divide string to single chars and put them in the array?

I realise it's pretty basic.
I need to ask user for an string input. Then I divide string to single char array and print it in a console. I have to ignore spaces
Tried this but when I input "this is test string" as output I get only {t h i s}
String tekst;
Scanner odczyt = new Scanner(System.in);
System.out.println("Wpisz tekst");
tekst = odczyt.next();
int iloscZnakow = tekst.length();
char tablica[] = new char[iloscZnakow];
tablica = tekst.toCharArray();
System.out.println(Arrays.toString(tablica));

You can use toCharArray() method of String class.

Please replace odczyt.next(); with odczyt.nextLine();

Need help splitting a string into two separate integers for processing

I am working on some data structures in java and I am a little stuck on how to split this string into two integers. Basically the user will enter a string like '1200:10'. I used indexOf to check if there is a : present, but now I need to take the number before the colon and set it to val and set the other number to rad. I think I should be using the substring or parseInt methods, but am unsure. The code below can also be viewed at http://pastebin.com/pJH76QBb
import java.util.Scanner; // Needed for accepting input
public class ProjectOneAndreD
{
public static void main(String[] args)
{
String input1;
char coln = ':';
int val=0, rad=0, answer=0, check1=0;
Scanner keyboard = new Scanner(System.in); //creates new scanner class
do
{
System.out.println("****************************************************");
System.out.println(" This is Project 1. Enjoy! "); //title
System.out.println("****************************************************\n\n");
System.out.println("Enter a number, : and then the radix, followed by the Enter key.");
System.out.println("INPUT EXAMPLE: 160:2 {ENTER} "); //example
System.out.print("INPUT: "); //prompts user input.
input1 = keyboard.nextLine(); //assigns input to string input1
check1=input1.indexOf(coln);
if(check1==-1)
{
System.out.println("I think you forgot the ':'.");
}
else
{
System.out.println("found ':'");
}
}while(check1==-1);
}
}

Substring would work, but I would recommend looking into String.split.
The split command will make an array of Strings, which you can then use parseInt to get the integer value of.
String.split takes a regex string, so you may not want to just throw in any string in it.
Try something like this:
"Your|String".split("\\|");, where | is the character that splits the two portions of the string.
The two backslashes will tell Java you want that exact character, not the regex interpretation of |. This only really matters for some characters, but it's safer.
Source: http://www.rgagnon.com/javadetails/java-0438.html
Hopefully this gets you started.

make this
if(check1==-1)
{
System.out.println("I think you forgot the ':'.");
}
else
{
String numbers [] = input1.split(":"); //if the user enter 1123:2342 this method
//will
// return array of String which contains two elements numbers[0] = "1123" and numbers[1]="2342"
System.out.print("first number = "+ numbers[0]);
System.out.print("Second number = "+ numbers[1]);
}

You knew where : is occurs using indexOf. Let's say string length is n and the : occurred at index i. Then ask for substring(int beginIndex, int endIndex) from 0 to i-1 and i+1 to n-1. Even simpler is to use String::split