Develop Reference

Type mismatch:could not convert from int to boolean

In the if statement, within the argument I get an error saying "type mismatch, could not convert from int to boolean". Please provide a solution.
public static void main(String[] args) {
Scanner sathya1 = new Scanner(System.in);
System.out.println("Enter the numbers");
int x = (sathya1.nextInt());
int y = (sathya1.nextInt());
int addition = x+y;
int subtraction = x-y;
int multiplication = x*y;
float division = x/y;
if(sathya1.nextInt(addition){
System.out.println("The number is " +addition);
elseif(sathya1.nextInt(subtraction)){
System.out.println("The number is " +subtraction);
elseif(sathya1.nextInt(multiplication)){
System.out.println("The number is " +multiplication);
elseif(sathya.1nextInt(division)){
System.out.println("The number is " +division);
}
}
}
}
}
}

The line
if(sathya1.nextInt(addition){
makes no sense. It's like saying "if 12". The same goes for the other lines. In addition, you're missing a closing ), among lots of other problems.

Maybe you mean:
import java.util.Scanner;
public class BasicArithmetic
{
public static void main(String[] args)
{
//create a scanner for keyboard input
Scanner sathya1 = new Scanner(System.in);
//ask user for the operation to be used
System.out.print("Please enter the corresponding number to be used \n(1)for Addition,(2)for Subtraction,(3)for Multiplication,(4)for Division:");
int enteredNumber = sathya1.nextInt();
//get the two numbers to be used
System.out.println("Enter the numbers");
float x = sathya1.nextFloat();
float y = sathya1.nextFloat();
//arithmetic operations of the two numbers
float addition = x+y;
float subtraction = x-y;
float multiplication =x*y;
float division = x/y;
//if..else statement
if(enteredNumber==1)
{
System.out.println("The sum of the two number is "+addition);
}
else if(enteredNumber==2)
{
System.out.println("The subtraction of the two number is "+subtraction);
}
else if(enteredNumber==3)
{
System.out.println("The product of the two number is "+multiplication);
}
else if(enteredNumber==4)
{
System.out.println("The quotient of the two number is "+division);
}
else
{
System.out.println("Please enter the correct corresponding number");
}
}
}

Creating Methods that will produce the same result

I'm in a Beginner Java class and I'm confused about using additional methods and using them in another. I think that I have most of my assignment done but I just need help to create the methods. One is to generate the question and the other one is to display the message.
I know that in order to call a method
public static test(num1,num2,num3)
but in my code, how do I make it so that I call the method and still make it loop correctly?
In the assignment instructions that was given to me, In order to do that, I have to write a method named
public static in generateQuestion()
and
public static void displayMessage(boolean isCorrect)
This is my code:
//For Random Generator
import java.util.Random;
//Uses a class Scanner
import java.util.Scanner;
public class Assign6
{
public static void main(String[] args)
{
//Scanner to Obtain Input from CW
Scanner input = new Scanner(System.in);
//Generate Random Number for Quiz
Random randomNumbers = new Random();
int number1 = 0;
int number2 = 0;
int answer = 0;
//Rolls number from 1-9
number1 = randomNumbers.nextInt(9);
number2 = randomNumbers.nextInt(9);
//Question prompt
System.out.println("How much is " +number1+ " times " +number2+ "? ");
answer = input.nextInt();
//If Else While Statements
if(answer == (number1*number2))
{
System.out.println("Good job! You got it right!");
}
else
{
while (answer !=(number1*number2))
{
System.out.println("You got it wrong, try again!");
answer = input.nextInt();
}
}
}
}

You are going to have two methods
public static void generateQuestion()
Which is going to hold the code to generate the random values and output it. It will return void because all it's doing is printing out.
Next you will have
public static void displayMessage(boolean isCorrect)
which will be called if if(answer == (number1*number2)) is true with true as the parameter. Otherwise it will still be called, but the parameter passed in will be false. This method will determine if isCorrect is true or false, and output the appropriate message.

If I got it right, I have a solution that might be a little stupid but will work for your assignment.
If you make generateQuestion that makes two random ints, prints the question and returns their multiple (answer).
And displayMessgae that prints "Good job! You got it right!" if isCorrect is true and "You got it wrong, try again!" else,
you can call generateQuestion, then get an answer (in main), and loop until answer is correct (according to return value of generateQuestion).
Every time you get a new answer (in loop), call displayMessgae(false).
After the loop ended call displayMessgae(true)
This is my working code for this:
//For Random Generator
import java.util.Random;
//Uses a class Scanner
import java.util.Scanner;
public class Assign6
{
public static int generateQuestion()
{
Random r = new Random();
int x = r.nextInt(9), y = x = r.nextInt(9);
System.out.println("How much is " + x + " times " + y + "? ");
return x * y;
}
public static void displayMessage(boolean isCorrect)
{
if (isCorrect)
System.out.println("Good job! You got it right!");
else
System.out.println("You got it wrong, try again!");
}
public static void main(String[] args)
{
//Scanner to Obtain Input from CW
Scanner input = new Scanner(System.in);
int rightAnswer = 0;
rightAnswer = generateQuestion();
while (input.nextInt() != rightAnswer)
displayMessage(false);
displayMessage(true);
}
}

If I understand your question correctly, It's simply a matter of separating the functionality that prints a question and displays the answer into separate methods. See my edited version of your code below
public class Assign6
{
public static void main(String[] args)
{
// Scanner to Obtain Input from CW
Scanner input = new Scanner(System.in);
// Generate Random Number for Quiz
Random randomNumbers = new Random();
int number1 = 0;
int number2 = 0;
int answer = 0;
// Rolls number from 1-9
number1 = randomNumbers.nextInt(9);
number2 = randomNumbers.nextInt(9);
displayQuestion("How much is " + number1 + " times " + number2 + "?");
answer = input.nextInt();
// If Else While Statements
if (answer == (number1 * number2))
{
displayMessage(Boolean.TRUE);
}
else
{
while (answer != (number1 * number2))
{
displayMessage(Boolean.FALSE);
answer = input.nextInt();
}
}
}
public static void displayQuestion(String q)
{
System.out.println(q);
}
public static void displayMessage(Boolean isCorrect)
{
if (isCorrect)
{
System.out.println("Good job! You got it right!");
}
else
{
System.out.println("You got it wrong, try again!");
}
}
}

Output will not print the correct information

I'm trying to make a program which asks the user a particular bird then how many of them they had seen at that point. If the use at any point enters the word 'END' then the system should print out the most seen bird and the number seen. However, when running my program if I enter 'END' at random points it instead returns that the most seen was END with 0 seen. I can't figure out how to make it work. I've tried different methods but it's just not working properly. Also, I've set the maximum array limit to 10 possitions but it continues after 10 and if i enter a value the system crashes. Have I written the limit part properly? Or am I missing something important?
import java.util.Scanner;
public class testing
{
public static void main (String[] param)
{
birdInput();
most();
System.exit(0);
}
public static void birdInput()
{
int i = 0;
String birdInput;
int numberInput;
Scanner scanner = new Scanner(System.in);
int maxVal = Integer.MIN_VALUE;
int maxValIndex = -1;
while (true)
{
System.out.println("What bird did you see?");
birdInput = scanner.nextLine();
if (birdInput.equals("END"))
{
System.out.print("\nWell....I guess thanks for using this program?\n");
System.exit(0);
}
else
{
String[] birds = new String[10];
int[] numbers = new int[10];
birds[i] = scanner.nextLine();
System.out.println("How many did you see?");
numbers[i] = scanner.nextInt();
i++;
if (birds[i].equals("END"))
{
maxVal = numbers[i];
maxValIndex = i;
System.out.print("\nThe most common bird that you saw was the " + birds[maxValIndex] + " with " + maxVal + " being seen in total\n");
System.exit(0);
}
}
}
}
public static void most()
{
System.out.println("fdff");
}
}
This is my edit of Till Hemmerich's answer to my issue. I tried to remove the global variables and so combine the entire code into 1 method. However, I'm still having some issues. Been working at it but really confused.
import java.util.Scanner;
public class birds2
{
public static void main(String[] param)
{
birdInput();
System.exit(0);
}
public static void birdInput()
{
Scanner scanner = new Scanner(System.in);
String[] birds = new String[99999999];
int[] numbers = new int[99999999];
int i = 0;
int maxIndex;
while (i <= birds.length)
{
System.out.println("What bird did you see?");
birds[i] = scanner.nextLine();
System.out.println("How many did you see?");
numbers[i] = scanner.nextInt();
i++;
}
int newnumber = numbers[i];
if ((newnumber > numbers.length))
{
maxIndex = i;
i++;
}
if (birds[i].toUpperCase().equals("END"))
{
System.out.print("\nWell....I guess thanks for using this program?\n");
System.out.print("\nThe most common bird that you saw was the " + birds[maxIndex] + " with " + numbers[maxIndex] + " being seen in total\n");
System.exit(0);
}
}
}

You're re-declaring the birds and numbers arrays in each iteration of the loop. They should be declared and initialized only once, before the loop.

I changed a lot so im going to explain my changes here in total.
First of all i had to move the Array Definition out of your while-loop as >mentioned above, since other wise you would override these Arrays every time.
I also made them globally accessible to work with them in other methods.
public static int maxIndex;
public static String[] birds = new String[10];
public static int[] numbers = new int[10];
in general I re structured the whole code a little bit to make it more readable and a little bit more object-orientated.
For example I created an method called inputCheck() which returns our input as a String and check if it equals END so you do not have to write your logic for this twice. (it also considers writing end lower or Uppercased by just Upper our input before checking it"if (input.toUpperCase().equals("END"))")
static String inputCheck() {
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
if (input.toUpperCase().equals("END")) {
end();
}
return input;
}
this method can now be called every time you need an input like this:
birds[i] = inputCheck();
but you need to be carefull if you want to get an integer out of it you first have to parse it like this:Integer.parseInt(inputCheck())
after that I wrote a method to search for the biggest Value in your numbers Array and getting its index:
public static int getMaxIndex(int[] numbers) {
for (int i = 0; i < numbers.length; i++) {
int newnumber = numbers[i];
if ((newnumber > numbers.length)) {
maxIndex = i;
}
}
return maxIndex;
}
it takes an int array as parameter and returns the index of the highest element in there as an Integer. Called like this:maxIndex = getMaxIndex(numbers);
Then after that I rewrote your end method. It now just calles our getMaxIndex method and prints some output to the console.
public static void end() {
maxIndex = getMaxIndex(numbers);
System.out.print("\nWell....I guess thanks for using this program?\n");
System.out.print("\nThe most common bird that you saw was the " + birds[maxIndex] + " with " + numbers[maxIndex] + " being seen in total\n");
System.exit(0);
}
to fix your last problem (crashing after more then 10 inputs)I changed your while-loop. Since your array only has 10 places to put things it crashes if you try to put information in place number 11. it not looks like this:while (i <= birds.length) instead of while (true) this way the max loops it can take is the amout of places Array birds has and it wont crash anymore.
public static void birdInput() {
int i = 0;
while (i <= birds.length) {
System.out.println("What bird did you see?");
birds[i] = inputCheck();
System.out.println("How many did you see?");
numbers[i] = Integer.parseInt(inputCheck()); //you should check here if its actuall a number otherwiese your programm will crash
i++;
}
}
Here is the whole code in total:
import java.util.Scanner;
/**
*
* #author E0268617
*/
public class JavaApplication1 {
public static int maxIndex;
public static String[] birds = new String[10];
public static int[] numbers = new int[10];
public static void main(String[] param) {
birdInput();
most();
System.exit(0);
}
public static void birdInput() {
int i = 0;
while (i <= birds.length) {
System.out.println("What bird did you see?");
birds[i] = inputCheck();
System.out.println("How many did you see?");
numbers[i] = Integer.parseInt(inputCheck()); //you should check here if its actuall a number otherwiese your programm will crash
i++;
}
}
static String inputCheck() {
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
if (input.toUpperCase().equals("END")) {
end();
}
return input;
}
public static int getMaxIndex(int[] numbers) {
for (int i = 0; i < numbers.length; i++) {
int newnumber = numbers[i];
if ((newnumber > numbers.length)) {
maxIndex = i;
}
}
return maxIndex;
}
public static void end() {
maxIndex = getMaxIndex(numbers);
System.out.print("\nWell....I guess thanks for using this program?\n");
System.out.print("\nThe most common bird that you saw was the " + birds[maxIndex] + " with " + numbers[maxIndex] + " being seen in total\n");
System.exit(0);
}
public static void most() {
System.out.println("fdff");
}
}
I hope you understand where the Problems had been hidden if you have any Questions hit me up.

Java fraction calculator, global variables?

This is my second time asking this question because this assignment is due tomorrow, and I am still unclear how to progress in my code! I am in an AP Computer programming class so I am a complete beginner at this. My goal (so far) is to multiply two fractions. Is there any way to use a variable inside a particular method outside of that method in another method? I hope that wasn't confusing, thank you!!
import java.util.Scanner;
import java.util.StringTokenizer;
public class javatest3 {
static int num1 = 0;
static int num2 = 0;
static int denom1 = 0;
static int denom2 = 0;
public static void main(String[] args){
System.out.println("Enter an expression (or \"quit\"): "); //prompts user for input
intro();
}
public static void intro(){
Scanner input = new Scanner(System.in);
String user= input.nextLine();
while (!user.equals("quit") & input.hasNextLine()){ //processes code when user input does not equal quit
StringTokenizer chunks = new StringTokenizer(user, " "); //parses by white space
String fraction1 = chunks.nextToken(); //first fraction
String operand = chunks.nextToken(); //operator
String fraction2 = chunks.nextToken(); //second fraction
System.out.println("Fraction 1: " + fraction1);
System.out.println("Operation: " + operand);
System.out.println("Fraction 2: " + fraction2);
System.out.println("Enter an expression (or \"quit\"): "); //prompts user for more input
while (user.contains("*")){
parse(fraction1);
parse(fraction2);
System.out.println("hi");
int num = num1 * num2;
int denom = denom1 * denom2;
System.out.println(num + "/" + denom);
user = input.next();
}
}
}
public static void parse(String fraction) {
if (fraction.contains("_")){
StringTokenizer mixed = new StringTokenizer(fraction, "_");
int wholeNumber = Integer.parseInt(mixed.nextToken());
System.out.println(wholeNumber);
String frac = mixed.nextToken();
System.out.println(frac);
StringTokenizer parseFraction = new StringTokenizer(frac, "/"); //parses by forward slash
int num = Integer.parseInt(parseFraction.nextToken());
System.out.println(num);
int denom = Integer.parseInt(parseFraction.nextToken());
System.out.println(denom);
}
else if (!fraction.contains("_") && fraction.contains("/")){
StringTokenizer parseFraction = new StringTokenizer(fraction, "/"); //parses by forward slash
int num = Integer.parseInt(parseFraction.nextToken());
System.out.println(num);
int denom = Integer.parseInt(parseFraction.nextToken());
System.out.println(denom);
}else{
StringTokenizer whiteSpace = new StringTokenizer(fraction, " ");
int num = Integer.parseInt(whiteSpace.nextToken());
System.out.println(num);
}
}}

Is there any way to use a variable inside a particular method outside of that method in another method?
Yes you can do that. You can declare a variable in a method, use it there and pass it to another method, where you might want to use it. Something like this
void test1() {
int var = 1;
System.out.println(var); // using it
test2(var); // calling other method and passing the value of var
}
void test2(int passedVarValue) {
System.out.println(passedVarValue); // using the passed value of the variable
// other stuffs
}

Basic Java questions Scanning

This is very basic java that i'm struggling with n00b style. it just prints out this
Please enter '.' when you want to calculate
1 2 3
.
Numbers are 1 2 3
The Sum is0The Product is1
when it is supposed to calculate the sum and product of those consecutive numbers. something is wrong id appreciate any help!
main method
import java.util.*;
public class NumberScanned {
public static void main(String[] args) {
System.out.println("Please enter '.' when you want to calculate");
Scanner keyboard = new Scanner(System.in);
String scannedString = keyboard.nextLine();
Scanning scanz= new Scanning(scannedString);
while(!keyboard.nextLine().equals("."))
{
scanz.set(scannedString);
}
keyboard.close();
System.out.println("Numbers are"+scannedString);
scanz.printState();
}
}
Class Scanning
public class Scanning {
int num;
int sum;
int product;
String userInput;
public Scanning(String userInput)
{
num=0;
sum=0;
product=1;
this.userInput=userInput;
}
public void set(String userInput)
{
for(int index=0; index<userInput.length(); index++)
{
if(Character.isDigit(userInput.charAt(index))==true)
{
num=userInput.charAt(index);
sum+=num;
product*=num;
}
else
{
index++;
}
}
}
public void printState()
{
System.out.println("The Sum is"+sum+"The Product is"+product);
}
}

A few things to look at:
We know keyboard.nextLine() gets the input from the console, but where are you checking it's validity (more importantly, when do you check it?). Are you looking at all input or just the last line?
isDigit will return true if the passed in character is a number. Do you want to operate on numbers or characters in your for loop?
(a side note, What happens if I enter "1 10" in the console?)
A for loop will automatically increment its index at the end of a loop, so an additional ++ is unnecessary

You might find this helful in case you just need the sum and product values of a user entered
values.
public class ProductSumCalculator{
private static List<Integer> numbers = new ArrayList<Integer>();
public static void main(String[] args){
getInputs();
calculateSumAndProduct();
}
private static void getInputs() {
Scanner scanner = new Scanner(System.in);
System.out.println("Please Enter numbers or ctrl+z to end inputs");
while(scanner.hasNext()){
numbers.add(scanner.nextInt());
}
}
private static void calculateSumAndProduct() {
Iterator<Integer> iterator = numbers.iterator();
int sum=0;
int product=1;
int nextVal;
while(iterator.hasNext()){
nextVal = iterator.next();
sum+=nextVal;
product*=nextVal;
}
System.out.println("Value entered are: "+numbers+".\nThe sum is "+
sum+".The product is "+product);
}
}

You can also try this. You can calculate the sum and product of all the int from your string line input like this:
import java.util.Scanner;
public class Scanning {
/*
* This method returns the integer. If while
* conversion an Exception is thrown it returns
* null. Otherwise the integer.
*/
public static Integer tryParse(String text) {
try {
return Integer.parseInt(text);
} catch (NumberFormatException e) {
return null;
}
}
/*
* Next String line is scanned. It is split by space.
* Stores String tokens in an String array from one String variable.
* Then passed to tryParse() class method. null or auto Boxed Integer
* is returned accordingly. It is auto unboxed from Integer
* object to int variable. Then sum and product is calculated and
* the final result is printed on the console Or Integrated
* Development Environment.
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner keyboard = new Scanner(System.in);
String strInts = keyboard.nextLine();
String[] splits = strInts.split("\\s+");
int i = 0;
Integer anInteger = null;
int total = 0;
int product = 1;
while((i < splits.length)) {
anInteger = tryParse(splits[i]);
if(anInteger != null) {
total = total + anInteger;
product = product * anInteger;
}
++i;
}
System.out.println("The sum is: " + total);
System.out.println("The product is: " + product);
}
}