My task is to write a java program that first asks the user how many numbers will be inputted, then outputs how many odd and even numbers that were entered. It is restricted to ints 0-100. My question is: What am I missing in my code?
import java.util.Scanner;
public class Clancy_Lab_06_03 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int n;
System.out.println("How many numbers will be entered?");
n = input.nextInt();
while (n < 0 || n > 100) {
System.out.println("ERROR! Valid range 0-100. RE-Enter:");
n = input.nextInt();
n++;
}
int odd = 0;
int even = 0;
while (n >= 0 || n <= 100) {
n = input.nextInt();
if (n % 2 == 0) {
even++;
} else {
odd++;
}
}
System.out.println(even + "even" + odd + "odd");
}
}
Second while loop is infinite. Relplace it with something like this:
for (int i = 0; i < n; i++) {
int b = input.nextInt();
if (b % 2 == 0) {
even++;
} else {
odd++;
}
}
Also I don't understand why are you incrementing n in first loop. For example when you will first give -5, you will be asked to re-enter the number. Then you type -1, but it gets incremented and in fact program processes 0, altough user typed -1. In my opinion it is not how it suppose to work and you should just remove this n++.
As you asked in comment - the same using while loop:
while(n > 0) {
n--;
int b = input.nextInt();
if (b % 2 == 0) {
even++;
} else {
odd++;
}
}
Also it is good idea to close input when you no longer need it (for example at the end of main method)
input.close();
You had two issues - first you were incrementing n in the first loop, rather than waiting for the user to enter a valid number.
In the second loop, you weren't comparing the number of entries the user WANTED to make with the number they HAD made - you were over-writing the former with the new number.
This version should work, although I've not tested it as I don't have java on this machine.
Note that we now sit and wait for both inputs, and use different variable names for the "how many numbers will you enter" (n) and "what is the next number you wish to enter" (num) variables? Along with a new variable i to keep track of how many numbers the user has entered.
import java.util.Scanner;
public class Clancy_Lab_06_03
{
public static void main (String[] args)
{
Scanner input = new Scanner (System.in);
int n;
System.out.println ("How many numbers will be entered?");
n = input.nextInt();
//Wait for a valid input
while (n < 0 || n > 100)
{
System.out.println ("ERROR! Valid range 0-100. RE-Enter:");
n = input.nextInt();
}
//Setup variables for the loop
int odd = 0;
int even = 0;
int num;
//Keep counting up until we hit n (where n is the number of entries the user just said they want to make)
for(int i = 0; i < n; i++)
{
//Changed this, because you were over-writing n (remember, n is the number of entries the user wants to make)
//Get a new input
while (num < 0 || num > 100)
{
System.out.println ("ERROR! Valid range 0-100. RE-Enter:");
num = input.nextInt();
}
//Check whether the user's input is even or odd
if (num % 2 == 0)
{
even++;
}
else
{
odd++;
}
}
System.out.println(even + " even. " + odd + " odd.");
}
}
import java.util.Scanner;
public class Test2 {
public static void main(String[] args) {
System.out.println("Enter an Integer number:");
Scanner input = new Scanner(System.in);
int num = input.nextInt();
if ( num % 2 == 0 )
System.out.println("Entered number is even");
else
System.out.println("Entered number is odd");
}
}
My suggestion to you is to have a clear separation of your requirements. From your post, you indicate you need to prompt the user for two distinct data items:
How many numbers will be entered (count)
The values to be analyzed
It is a good practice, especially when you are learning, to use meaningful names for your variables. You are using 'n' for a variable name, then reusing it for different purposes during execution. For you, it is obvious it was difficult to figure out what was 'n' at a particular part of the program.
Scanner input = new Scanner (System.in);
int count;
System.out.println ("How many numbers will be entered?");
count = input.nextInt();
//Wait for a valid input
while (count < 1 || count > 100)
{
System.out.println ("ERROR! Valid range 1-100. RE-Enter:");
count = input.nextInt();
}
Additionally, a count of zero should not be valid. It does not make sense to run a program to evaluate zero values (don't bother a program that does nothing). I believe the lowest count should be one instead.
int odd = 0;
int even = 0;
int value;
do
{
System.out.print("Enter a number between 0 and 100: ");
value = input.nextInt();
while (value < 0 || value > 100)
{
System.out.println ("ERROR! Valid range 0-100. RE-Enter:");
value = input.nextInt();
}
if (value % 2 == 0)
{
even++;
}
else
{
odd++;
}
count--; // decrement count to escape loop
} while (count > 0);
System.out.println(even + " even. " + odd + " odd.");
This example uses a do/while loop because in this case, it is OK to enter the loop at least once. This is because you do not allow the user to enter an invalid number of iterations in the first part of the program. I use that count variable directly for loop control (by decrementing its value down to 0), rather than creating another variable for loop control (for instance , 'i').
Another thing, slightly off topic, is that your requirements were not clear. You only indicated that the value was bounded to (inclusive) values between 0 and 100. However, how many times you needed to repeat the evaluation was not really clear. Most people assume 100 was also the upper bound for your counter variable. Because the requirement is not clear, checking a value greater or equal to 1 for the count might be valid, although highly improbable (you don't really want to repeat a million times).
Lastly, you have to pay attention to AND and OR logic in your code. As it was indicated, your second while loop:
while (n >= 0 || n <= 100) {}
Is infinite. Because an OR evaluation only needs one part to evaluate to TRUE, any number entered will allow the loop to continue. Obviously, the intent was not allow values greater than 100. However, entering 150 allows the loop to continue because 150 >= 0. Likewise, -90 also allows the loop to continue because -90 <= 100. This is when pseudocode helps when you are learning. You wanted to express "a VALUE between lower_limit AND upper_limit." If you reverse the logic to evaluate values outside the limit, then you can say " value below lower_limit OR above upper_limit." These pseudocode expressions are very helpful determining which logical operator you need.
I also took the liberty to add a message to prompt the user for a value. Your program expects the user to enter two numbers (count and value) but only one prompt message is provided; unless they enter an out of range value.
extract even numbers from arrayList
ArrayList numberList = new ArrayList<>(Arrays.asList(1,2,3,4,5,6));
numberList.stream().filter(i -> i % 2 == 0).forEach(System.out::println);
Related
I am new to Java and just learning the basics.
I have gone through if checks/statements(if-if-if; if-else if-else, if-else), while and for loops as well. I have an assignment which I can not for the life of me figure out. I am having some issues with the flow of the program itself and I just get it to work half way through in Eclipse.
The idea of the program is for it to accept three integers from the keyboard(keyboard input using Scanner) and print out all numbers, between 0 and the first integer from the input, which can be divided by the second and third input integers, respectively. The first input integer has to be between 200 and 100. I will provide what code I have written. I can get the program to accept input but then I get the message in the console.
I set up the three integers, I set up a condition for the first integer using a while loop and then I use a for loop to print all the numbers between 0 and the first input integer. Then within the for loop I do in if check and print out all the numbers. It accepts the input three times but then I just goes to terminated status.
package Javawork;
import java.util.Scanner;
public class Test {
private static Scanner keyboard;
public static void main(String[] args) {
firstProgramme();
}
public static void firstProgramme() {
keyboard = new Scanner(System.in);
System.out.println("Enter number: ");
int firstNum = keyboard.nextInt();
int secondNum = keyboard.nextInt();
int thirdNum = keyboard.nextInt();
while (firstNum > 100 && firstNum < 200) {
for (int i = 0; i <= firstNum; i++) {
if (i % secondNum == 0 && i % thirdNum == 0) {
System.out.println(i);
}
}
}
}
}
As per your requirement you need to check whether the first number is between 100 and 200. For that you should use
if(firstNum > 100 && firstNum < 200) {
instead of
while(firstNum > 100 && firstNum < 200) {
As if will check the condition and while will iterate based on condition.
I am creating a program that prints the sum of the even numbers from a range of 0 to the number that the user entered. For example, if the user entered the number 20, the program would calculate the sum of all of the even numbers between 0 and 20.
When I tested the program out with the number 10, it worked. But I tried using a different number, 35, and it was just stuck in an infinite loop. I would appreciate any and all help. The code will be posted below:
(Edit) Thanks for the feedback everyone! After talking with a friend, we realized that the solution is actually pretty simple. We were just making it complicated. Still, thanks for all of the suggestions.
//**************************************************************
// Prints the sum of the even numbers within a range of 0
// and the integer that the user enters.
//
// #me
// #version_1.0_11.7.17
//**************************************************************
import java.util.Scanner;
public class EvenNumbersSum
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int user_num = 2; // variable that stores the user's number
int sum; // stores the sum of the needed values
System.out.print("Enter an integer greater than or equal to, 2: "); // prompt user for input
user_num = input.nextInt();
// checks to see if the value entered is valid or not.
while (user_num < 2)
{
System.out.println("Invalid entry. Must enter an integer greater than or equal to, 2.\n");
System.out.print("Enter an integer greater than or equal to, 2: ");
user_num = input.nextInt();
}
// starts adding the values
for (sum = 0; sum <= user_num;)
{
if (user_num % 2 == 0) // checks if the number is even
sum+=user_num; // add the number to sum
else
continue; // I thought that I might need this, but ended up changing nothing.
}
System.out.println(); // extra line for cleanliness
System.out.printf("The sum of the even numbers between 0 and %d is %d.", user_num, sum); // prints the result
}
}
Why are you writing loop for this, there are efficient way to do it.
Sum of numbers between 1-N = (N(N+1))/2
Sum of even numbers between 1-N = (N(N+2))/4
where N = user given input number till which you would like to add even numbers
NOTE: you can add validation on input number that it’s even by (n%2 == 0) and return error if it’s not
The variable you have used in condition (i.e. sum & user_num) no one changes in case of odd number and your code stuck in never-ending loop.
You should use counter variable ( e.g. i from 1 to user_num) and use that number in the condition. Example:
// starts adding the values
sum = 0;
for (int i = 0; i <= user_num; i++)
{
if (i % 2 == 0) // checks if the number is even
sum+=i; // add the number to sum
}
Your for loop should be like this.
int total_sum = 0;
for (int sum = 0; sum <= user_num; sum++)
{
if (sum % 2 == 0) // checks if the number is even
total_sum+=sum; // add the number to total sum
else
continue; // I thought that I might need this, but ended up changing nothing.
}
// note print total sum
System.out.println(totalsum);
your initial program just kept on checking entered number is even or odd.
And the entered number to sum.
So sum was always double of the entered number is even.
If entered number is odd it would go to infinite loop as entered_num(odd) % 2 == 0 always false and execute else statement.
Firstly, I'm taking AP Computer Science this year, and this question is related to an exercise we were assigned in class. I have written the code, and verified that it meets the requirements to my knowledge, so this is not a topic searching for homework answers.
What I'm looking for is to see if there's a much simpler way to do this, or if there's anything I could improve on in writing my code. Any tips would be greatly appreciated, specific questions asked below the code.
The exercise is as follows: Write a program called ProcessingNumbers that does:
Accepts a user input as a string of numbers
Prints the smallest and largest of all the numbers supplied by the user
Print the sum of all the even numbers the user typed, along with the largest even number typed.
Here is the code:
import java.util.*;
public class ProcessingNumbers {
public static void main(String[] args) {
// Initialize variables and objects
Scanner sc = new Scanner(System.in);
ArrayList<Integer> al = new ArrayList();
int sumOfEven = 0;
// Initial input
System.out.print("Please input 10 integers, separated by spaces.");
// Stores 10 values from the scanner in the ArrayList
for(int i = 0; i < 10; i++) {
al.add(sc.nextInt());
}
// Sorts in ascending order
Collections.sort(al);
// Smallest and largest values section
int smallest = al.get(0);
int largest = al.get(al.size() - 1);
System.out.println("Your smallest value is " + smallest + " and your largest value is " + largest);
// Sum of Even numbers
int arrayLength = al.size();
for (int i = 0; i < al.size(); i++) {
if (al.get(i) % 2 == 0) {
sumOfEven += al.get(i);
}
}
System.out.println("The sum of all even numbers is " + sumOfEven);
// Last section, greatest even number
if (al.get(arrayLength - 1) % 2 == 0) {
System.out.println("The greatest even number typed is " + al.get(arrayLength - 1));
} else {
System.out.println("The greatest even number typed is " + al.get(arrayLength - 2));
}
sc.close();
}
}
Here are specific questions I'd like answered, if possible:
Did I overthink this? Was there a much simpler, more streamlined way to solve the problem?
Was the use of an ArrayList mostly necessary? We haven't learned about them yet, I did get approval from my teacher to use them though.
How could I possibly code it so that there is no 10 integer limit?
This is my first time on Stackoverflow in quite some time, so let me know if anything's out of order.
Any advice is appreciated. Thanks!
Usage of the ArrayList wasn't necessary, however it does make it much simpler due to Collections.sort().
To remove the 10 integer limit you can ask the user how many numbers they want to enter:
int numbersToEnter = sc.nextInt();
for(int i = 0; i < numbersToEnter; i++) {
al.add(sc.nextInt());
}
Another note is that your last if-else to get the highest even integer doesn't work, you want to use a for loop, something like this:
for (int i = al.size() - 1; i >= 0; i--) {
if (al.get(i) % 2 == 0) {
System.out.println("The greatest even number typed is " + al.get(i));
break;
}
I wouldn't say so. Your code is pretty straightforward and simple. You could break it up into separate methods to make it cleaner and more organized, though that isn't necessary unless you have sections of code that have to be run repeatedly or if you have long sections of code cluttering up your main method. You also could have just used al.size() instead of creating arrayLength.
It wasn't entirely necessary, though it is convenient. Now, regarding your next question, you definitely do want to use an ArrayList rather than a regular array if you want it to have a variable size, since arrays are created with a fixed size which can't be changed.
Here's an example:
int number;
System.out.print("Please input some integers, separated by spaces, followed by -1.");
number = sc.nextInt();
while (number != -1) {
al.add(number);
number = sc.nextInt();
}
Here is a solution that:
Doesn't use Scanner (it's a heavyweight when all you need is a line of text)
Doesn't have a strict limit to the number of numbers
Doesn't need to ask how many numbers
Doesn't waste space/time on a List
Handles the case when no numbers are entered
Handles the case when no even numbers are entered
Fails with NumberFormatException if non-integer is entered
Moved actual logic to separate method, so it can be mass tested
public static void main(String[] args) throws Exception {
System.out.println("Enter numbers, separated by spaces:");
processNumbers(new BufferedReader(new InputStreamReader(System.in)).readLine());
}
public static void processNumbers(String numbers) {
int min = 0, max = 0, sumOfEven = 0, maxEven = 1, count = 0;
if (! numbers.trim().isEmpty())
for (String value : numbers.trim().split("\\s+")) {
int number = Integer.parseInt(value);
if (count++ == 0)
min = max = number;
else if (number < min)
min = number;
else if (number > max)
max = number;
if ((number & 1) == 0) {
sumOfEven += number;
if (maxEven == 1 || number > maxEven)
maxEven = number;
}
}
if (count == 0)
System.out.println("No numbers entered");
else {
System.out.println("Smallest number: " + min);
System.out.println("Largest number: " + max);
if (maxEven == 1)
System.out.println("No even numbers entered");
else {
System.out.println("Sum of even numbers: " + sumOfEven);
System.out.println("Largest even number: " + maxEven);
}
}
}
Tests
Enter numbers, separated by spaces:
1 2 3 4 5 6 7 8 9 9
Smallest number: 1
Largest number: 9
Sum of even numbers: 20
Largest even number: 8
Enter numbers, separated by spaces:
1 3 5 7 9
Smallest number: 1
Largest number: 9
No even numbers entered
Enter numbers, separated by spaces:
-9 -8 -7 -6 -5 -4
Smallest number: -9
Largest number: -4
Sum of even numbers: -18
Largest even number: -4
Enter numbers, separated by spaces:
No numbers entered
I'm really new to this whole programming thing, and I'm trying to wrap my head around why the loop ends abruptly and does not continue to the final if statement. Can you guys help me figure out whats wrong?
import java.util.Scanner;
public class FunnyAverage {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("How many values to read? ");
int top = in.nextInt();
System.out.print("Enter Value: ");
int one = in.nextInt();
int number = 1;
int sum = 0;
sum = sum + one;
while (number <= top) {
if (one % 6 != 0 && one % 17 != 0) {
System.out.print("Enter Value: ");
one = in.nextInt();
number++;
} else if (one % 6 == 0 && one % 17 == 0) {
System.out.print("Enter Value: ");
one = in.nextInt();
number++;
}
}
if (sum / top != 0) {
System.out.print("Average: " + sum / top);
}
System.out.print("None Divisible");
}
}
The final if() condition executes if you give the right input values. I ran your code and gave the below inputs to execute the final if() statement.
How many values to read? 1
Enter Value: 1
Enter Value: 1
Average: 1None Divisible
I dont understand what are you trying in the code, but there are many things missing like i assume you want to capture the sum of the input numbers, but sum is not used in the while loop.
Looks like you end up in the non-present else case (within the while loop). Consequently, number isn't increased and you are stuck in the while loop.
Try reading one within the while loop. This way the user will be prompted to enter a new number in each loop.
Otherwise you will be stuck in the while loop once the user enters a number that isn't conform with your checks.
for these guidelines:
Write a loop that reads positive integers from standard input and that terminates when it reads an integer that is not positive. After the loop terminates, it prints out, separated by a space and on a single line, the sum of all the even integers read and the sum of all the odd integers read. Declare any variables that are needed.
ASSUME the availability of a variable, stdin , that references a Scanner object associated with standard input.
I wrote this code, but it the HW software will not except it due to a logical error. I cant seem to find the logical error here. can someone point out what is wrong with it?
int sumP=0;
int sumO=0;
Scanner stdin = new Scanner (System.in);
System.out.println("enter an odd or even number");
while (stdin.nextInt() >= 0){
if(stdin.nextInt()%2 == 0)
sumP+= stdin.nextInt();
else
sumO += stdin.nextInt();
}
System.out.println(sumP + " " + sumO);
You need to save the value you have read, otherwise you will be used different values in the while loop and the addition.
int n;
while((n = stdin.readInt()) >= 0) {
// use the same value of n
This worked for myprogramminglab - Java
int sum=0;
boolean areMore = true;
int negative;
while (areMore)
{
int number = stdin.nextInt();
if (number <= 0)
areMore = false;
else if (number %2 ==0 )
sum = sum + number;
else
negative = sum + number;
}
System.out.println(sum);
int number = 1;
while (stdin.hasNextInt() && number > 0)
{
number = stdin.nextInt();
if (number % 2 == 0 && number > 0)
System.out.print(number + " ");
}
The answer to this and many other codelab exercises can be found at Java Codelab Solutions