We Keep Coding

Why does my CalcOddIntegers method always return zero?

This method is supposed to take user input for the length of the array, and then the integers that are part of the array, and return the amount of odd numbers in the array. However, it always returns zero for the count of odd integers and I am unsure as to why. The scanner is declared outside of this method.
System.out.print("Enter length of sequence\n");
int length = console.nextInt();
int[] array = new int[length];
System.out.print("Enter the sequence: \n");
int count = 0;
int i = 0;
for (i = 0; i < length; i++) {
array[i] = console.nextInt();
}
for (i = 0; i < length -1; i++); {
if (array[i] % 2 != 0) {
count++;
}
}
System.out.printf("The count of odd integers in the sequence is %d\n", count);
}
Example of console:
2. Calculate the factorial of a given number
3. Calculate the amount of odd integers in a given sequence
4. Display the leftmost digit of a given number
5. Calculate the greatest common divisor of two given integers
6. Quit
3
Enter length of sequence
4
Enter the sequence:
1
2
3
4
The count of odd integers in the sequence is 0
I have tried experimenting with the for statements with different variables to see if something was conflicting but nothing has worked.

Remove the semi-colon (;) in the line
for (i = 0; i < length -1; i++);
the semi-colon terminates the loop hence an assumption that your line does nothing.

After the second for there is a semicolon that shouldn't be there. The syntax is technically correct however, there is nothing to execute so the block that checks for odd numbers is going to be executed only once. I suggest using a debugger that will help you troubleshoot issues easier.

Java method to calculate the square root via minuend and subtrahend and print each step

I am tasked with creating a program in java which calculates the square root of a double and goes through each step of calculating it manually. The requirements are:
split the number into number pairs including the decimal point (1234.67 -> 12 34 67) to prepare for subtraction. If the number is uneven, a zero must populate (234.67 -> 02 34 67)
Print each pair (each pair is a minuend), one at a time, into the console and have the console show the subtraction. Subtrahend starts at 1 and so long as the result >= 0, the subtrahend increases by 2.
The count of subtrahends is the first number of the final square root output, the count of subtrahends from the second round is the second number of the square root output, etc.
From the first subtrahend round, take the remainder and join it to the second number pair, this is the new minuend for the second round of subtraction
Calculate the second subtrahend in round two by doubling the first number of the square root output and adding 1 in the first digit position
Repeat step 2, increasing by 2 each time
Step 5 and 6 repeat until two decimal places are reached
My question is with the number pairs in step 1 and getting the subsequent subtrahends after step 3 as a number to calculate. We are given the following visual:
My current thought is to put the double into a string and then tell java that each number pair is a number. I have a method created which creates a string from a double, but I am still missing how to incorporate the decimal place numbers. From my C class, I remember multiplying decimals by 100 to "store" the decimal numbers before converting them back later with another division by 100. I'm sure there is a java library that is able to do this but we are specifically not allowed to use them.
I think I should be able to continue on with the rest of the problem once I get past this point of splitting the number into number pairs inclusive of the decimals.
This is also my first stack post so if you have any tips on how to better write questions for future posts that would be helpful as well.
This is my current array method to store a given double into an array:
public static void printArray(int [] a) //printer helper method
{
for(int i = 0; i < a.length; i++)
{
System.out.print(a[i]);
}
}
public static void stringDigits (double n) //begin string method
{
int a [] = new int [15];
int i = 0;
int stringLength = 0;
while(n > 1)
{
a[i] = (int) (n % 10);
n = n / 10;
i++;
}
for(int j = 0; a[j] != 0; j++)
{
System.out.print(a[j]);
if(a[j] != 0)
{
stringLength++;
}
}
System.out.println("");
System.out.println(stringLength);
int[] numbersArray = new int[stringLength];
int g = 0;
for(int k = a.length-1; g < numbersArray.length; k--)
{
if(a[k] > 0)
{
numbersArray[g] = a[k];
g++;
}
}
System.out.println("");
printArray(numbersArray);
}
I've tried at first to store the value of the double into an int[] a array so that I can then select the numbers in pairs and then somehow combine them back into numbers. So if the array is {1,2,3,4,5,6} my next idea is to get java to convert a[0] + a[1] into the number 12 to prepare for the subtraction step.
This link looks close but does anyone know why the numbers are "10l" and "100l" etc? I've tested some of the answers and they dont produce the proper squareroot compared to the sqrt function from the math library.
Create a program that calculates the square root of a number without using Math.sqrt

Java program infinite loop in sum of even integers

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.

Taking average of user input number

This is my code
import java.util.*;
import java.io.*;
public class eCheck10A
{
public static void main(String[] args)
{
PrintStream out = System.out;
Scanner in = new Scanner(System.in);
out.print("Enter your integers");
out.println("Negative = sentinel");
List<Integer> aList = new ArrayList<Integer>();
for (int n1 = in.nextInt(); n1 > 0; n1 = in.nextInt())
{
if(n1 < 0)
{
break;
}
}
}
}
if i want to take all the numbers that I enter for n1, and average them out, how do i refer to all these numbers? I am going to put them in the IF statement, so if a negative number is entered, the program stops and posts their average.

This is the pseudocode you need to do this task (pseudo-code since it looks suspiciously like homework/classwork and you'll become a better developer if you nut out the implementation yourself).
Because you don't need the numbers themselves to work out the average, there's no point in storing them. The average is defined as the sum of all numbers divided by their count, so that's all you need to remember. Something like this should suffice:
total = 0
count = 0
n1 = get_next_number()
while n1 >= 0:
total = total + n1
count = count + 1
n1 = get_next_number()
if count == 0:
print "No numbers were entered.
else:
print "Average is ", (total / count)
A couple of other points I'll mention. As it stands now, your for statement will exit at the first non-positive number (<= 0), making the if superfluous.
In addition, you probably want any zeros to be included in the average: the average of {1,2,3} = 2 is not the same as the average of {1,2,3,0,0,0} = 1.
You can do this in the for statement itself with something like:
for (int n1 = in.nextInt(); n1 >= 0; n1 = in.nextInt())
and then you don't need the if/break bit inside the loop at all, similar to my provided pseudo-code.

An outline of what you will need to do: Create a variable sum to add up all of the values and create another variable called count that will be used to store the number of non-negative numbers in your list, aList. Then divide the sum by the count to find the average.

Another way to do running average is:
new_average = old_average + (new_number - old_average ) / count
If you ever hit max for a variable type, you would appreciate this formula.

I need to make two to the input value inclusive

/*
* Application the reads an integer and prints sum of all even integers between two and input value
*/
import java.util.Scanner;
public class evenNumbers{
public static void main(String [] args){
int number;
Scanner scan = new Scanner(System.in);
System.out.println("Enter an Integer greater than 1:");
number = scan.nextInt();
printNumber(number);
}// end main
/*declares an int variable called number and displays it on the screen*/
public static void printNumber(int number){
if (number < 2){
System.out.println("Input value must not be less than 2");
}
int sum = 2;
if(number % 2==0){
sum+= number;
}
System.out.println("Sum of even numbers between 2 and " + number + " inclusive is: " + sum);
}//end printnumber
}
I need to calculate the sum of 2 to the input number inclusive however, it only takes the last number and add two to it. COuld someone help me fix this.

You need a loop. Your comment hints at the right direction, but you should look at the Java tutorials to see how to correctly write a 'for' loop. There are three parts: the initial declaration, the terminating condition and the loop step. Remember that the ++ operator only adds one to the variable. You can add other values using +=. If you use += to add a different value (like 2) to the loop variable, you can skip the 'if' test for even numbers. You can test for boundaries inclusively using the <= and >= comparison operators (for primitives). So you want something like this (in pseudocode, not Java):
input the test value
Optional: reject invalid test value and **exit with message if it is not valid!**
initialize the sum variable to zero
for ( intialize loop variable to 2; test that loop var <= test value; add 2 to loop var )
{
add 'number' to the sum variable
}
display the sum

int sum = 0;
for (int current = 2; current <= number; current += 2)
sum += current;