Develop Reference

Java: How to get back to the main method after using other methods

I'm fairly new to Java and the problem I am having is that this code compiles, but does not run after the hexadecimal conversion; it instead just ends after the method hexCharToDecimal. I can't reuse method main and I'm not sure how to call the method intreverse and actually have it run. Is there a way to get back into main or do I have to call intreverse somewhere?
import java.util.Scanner;
public class Homework4 {
public static void main(String[]args) {
// Sum and average of a set of intergers entered by the user
// First we will declare some variables
int userInput = 1;
int positives = 0;
int negatives = 0;
int sum = 0;
int numCount = 0;
Scanner input = new Scanner(System.in);
// Will start a while loop that will stop when user enters 20 integers
while ((numCount <= 20)) {
System.out.println("Please enter a nonzero integer or enter 0 to finish ");
userInput = input.nextInt();
if (userInput == 0) {
break;
} else if (userInput > 0) {
positives += 1;
numCount += 1;
sum = sum + userInput;
} else if (userInput < 0) {
negatives += 1;
numCount += 1;
sum = sum + userInput;
} else
System.out.println("Error, please enter an integer");
continue;
}
double average = (sum / numCount);
System.out.println("The sum of the entered integers is " + sum);
System.out.println("The average of the enetered integers is " + average);
System.out.println("There are " + positives + " positive integers and " + negatives + " negative integers");
// Convert Hexadecimal number to decimal
// Ask the user to input a string of 5 digits or less in hex
System.out.println("Please enter a hexadecimal number of up to 5 characters");
String hex = input.next();
if (hex.length() <= 5) {
System.out.println(hex + " in decimal value is equal to " + hexToDecimal(hex.toUpperCase()));
} else {
System.out.println("Error: please enter a hex number of 5 digits or less");
}
}
// Now we will create the method to convert to decimal
public static int hexToDecimal(String hex) {
int decimal = 0;
for (int i = 0; i < hex.length(); i++) {
char hexcharacter = hex.charAt(i);
decimal = decimal * 16 + hexCharToDecimal(hexcharacter);
}
return decimal;
}
public static int hexCharToDecimal(char ch) {
if (ch >= 'A' && ch <= 'F') // check to see if there is any letters in the string
return 10 + ch - 'A';
else
return ch - '0';
}
// Print entered integer in reverse
public static void intreverse(String[]args) {
// Ask user for an integer to be reversed
Scanner input = new Scanner(System.in);
System.out.println("Please enter an integer to be reversed");
int number = input.nextInt();
reverse(number); // Method to be called
}
// Will now state our method
public static void reverse(int number) {
// use a while loop to get each digit
while (number > 0) {
System.out.print(number % 10);
number = number / 10;
}
}
}

if (hex.length() <= 5) {
System.out.println(hex + " in decimal value is equal to " + hexToDecimal(hex.toUpperCase()));
} else {
System.out.println("Error: please enter a hex number of 5 digits or less");
}
Will always run once because it is not enclosed in any sort of loop. If you want it to run again when the second case is called then enclose it in a while(true) loop and have a break statement in the first case where you want it to stop execution.

Why isn't my Java number input code working?

I have been trying to figure out why isn't my code working. If I don't do it through a method and put this code in the main method then it keeps repeating. I want to ask the user for a new number every time. And then see if the number is odd or even. If odd then increase the odd count add all the numbers that the user enters. The user should be asked to enter values until the number 0 is entered.
package Week1;
import java.util.Scanner;
public class Task12 {
public void numbers() {
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();
System.out.println("Enter number");
int oddnumbers = 0;
do {
int count = 0;
count = count + i;
System.out.println("The total is:" + count);
if (i % 2 == 0) {
System.out.println("The number is Even");
} else if (i != 9) {
oddnumbers += i;
System.out.println("The number is odd");
System.out.println("the count of odd numbers is :" + oddnumbers);
} else
System.out.println("The number is odd");
System.out.println("the count of odd numbers is :" + oddnumbers);
} while (i != 0);
}
public static void main(String[] args) {
Task12 n = new Task12();
n.numbers();
}
}

You should probably have the reading of a number "i = sc.nextInt();" inside the loop, and the variable count outside, like this:
package Week1;
import java.util.Scanner;
public class Task12 {
public void numbers() {
Scanner sc = new Scanner(System.in);
int oddnumbers = 0;
int count = 0;
int i=0;
do {
System.out.println("Enter number");
i = sc.nextInt();
count = count + i;
System.out.println("The total is:" + count);
if (i % 2 == 0) {
System.out.println("The number is Even");
} else if (i != 9) {
oddnumbers += i;
System.out.println("The number is odd");
System.out.println("the count of odd numbers is :" + oddnumbers);
} else
System.out.println("The number is odd");
System.out.println("the count of odd numbers is :" + oddnumbers);
} while (i != 0);
}
public static void main(String[] args) {
Task12 n = new Task12();
n.numbers();
}
}

This code gives the answer to tour spec/question
Reason for not working: You should take input inside do while loop and then check for odd.
public int numbers() {
Scanner sc = new Scanner(System.in);
int num = 0;
int oddSum = 0;
do {
System.out.println("Enter number");
num = sc.nextInt();
if(num == 0) {
break;
} else if (num % 2 != 0) {
oddSum += num;
}
} while (num != 0);
sc.close();
return oddSum;
}
public static void main(String[] args) {
Test n = new Test();
System.out.println(n.numbers());
}

Java addition program which keeps addup the numbers you input ing until you enter a zero. Average of SumPositive and SumNegative

In this java program you (the user) keeps entering numbers until you enter a zero, which is when the list terminates. It will compute the sum of positive even & sum of odd even and negative numbers. It will also compute the average.
I'm stuck at the part to get the average of sum of even positive numbers, sum of odd positive numbers, and sum of negative numbers.
import java.util.*;
class sumPositiveAverage {
public static void main (String[] args) {
Scanner sc = new Scanner (System.in);
System.out.println ("Enter numbers. List terminates when you enter a zero.
Enter a zero when you want to begin the addition.");
int a = sc.nextInt();
int esum=0;
int osum=0;
int nsum=0;
while (a !=0)
{
if (a>0)
{
if (a%2==0)
{
esum = esum+a;
}// end of 3rd innermost if statement
else
{
osum = osum+a;
}// end of 3rd else statement
}//end of 2nd middle if-else-loop
else if (a<0)
{
nsum=nsum+a;
}//end of 2nd middle else statement
}//end of while loop
System.out.println ("The sum of even positive numbers is "+esum);
System.out.println ("The sum of odd positive numbers is "+osum);
System.out.println ("The sum of negative numbers is "+nsum);
}//end of main
}//end of class2

import java.util.*;
public class sumPositiveAverage {
public static void main(String[] args)
{
int sum_even = 0;
int sum_odd = 0;
int sum_negative = 0;
int sum_positive = 0;
int count_even = 0;
int count_odd = 0;
int count_negative = 0;
int count_positive = 0;
double avg_sum_even = 0;
double avg_sum_odd = 0;
double avg_sum_negative = 0;
double avg_sum_positive = 0;
int sum = 0;
int count = 0;
Scanner input = new Scanner(System.in);
int data = 0;
do
{
System.out.print("Type in a positive or negative number and press enter key, if 0 is entered program stops: ");
data = input.nextInt();
if(data > 0){
if(data%2 == 0){
//even number
sum_even = sum_even + data;
count_even++;
}else{
//odd
sum_odd = sum_odd + data;
count_odd++;
}
sum_positive = sum_positive + data;
count_positive++;
}else if(data < 0) {
//negative number
sum_negative = sum_negative + data;
count_negative++;
}
}
//Stops if the value of data is ZERO(0) and continues if it's not
while(data != 0);
//here means zero has been entered
if(count_positive > 0) { avg_sum_positive = (double)sum_positive/count_positive; }
if(count_negative > 0) { avg_sum_negative = (double)sum_negative/count_negative; }
if(count_even > 0) { avg_sum_even = (double)sum_even/count_even; }
if(count_odd > 0) { avg_sum_odd = (double)sum_odd/count_odd; }
System.out.println("Sum of Positive Numbers = " + sum_positive);
System.out.println("Sum of negative Numbers = " + sum_negative);
System.out.println("Sum of odd Numbers = " + sum_odd);
System.out.println("Sum of even Numbers = " + sum_even);
System.out.println("Count of Positive Numbers = " + count_positive);
System.out.println("Count of negative Numbers = " + count_negative);
System.out.println("Count of odd Numbers = " + count_odd);
System.out.println("Count of even Numbers = " + count_even);
System.out.println("Average of Positive Numbers = " + avg_sum_positive);
System.out.println("Average of negative Numbers = " + avg_sum_negative);
System.out.println("Average of odd Numbers = " + avg_sum_odd);
System.out.println("Average of even Numbers = " + avg_sum_even);
}//closing main
} // closing class

Taking scanner input and outputting min and max

so I'm trying to find the min, max, and average number of the numbers input. Everything works fine, although I do not want input less than 0 or greater than 100. When I input a number less than 0 or greater than 100 it still records it as the min/max. I do not want this! How would I not take input that is less than 0 or greater than 100?
Thanks!
import java.text.DecimalFormat;
import java.util.Scanner;
public class ExamGrades {
public static void main(String[]args){
Scanner scan = new Scanner(System.in );
int number = 0;
double total = 0;
int minimum;
int maximum = 0;
System.out.println("Please enter the first integer: ");
number = scan.nextInt();
minimum=number;
total += number;
for(int i = 2; i<11; i++){
if(number<0 || number >100){
System.out.println("Please enter a valid number: ");
number = scan.nextInt();
i--;
}
else{
System.out.println("Please enter integer " + i + ":");
number = scan.nextInt();
total += number;
if(number<minimum)
minimum = number;
if(number>maximum)
maximum = number;
}
}
DecimalFormat oneDecimalPlace = new DecimalFormat("##.#");
System.out.println("The minimum is: " + minimum);
System.out.println("The maximum is: " + maximum);
System.out.println("The average is: " + oneDecimalPlace.format((total) / 10.0 ));
}
}

Let's say you entered 5 for integer one, then 102 for the second integer. What's going to happen? Well before you entered 102, number was 5, so it will go into the else block.
It'll say:
Please enter integer 2:
then you type: 102
So then what? Well the next piece of code is:
number = scan.nextInt(); and then it goes through the if-statements right below it to determine if it's a maximum. Nothing is stopping it.
Try this code instead of your loop:
System.out.println("Please enter the first integer: ");
number = scan.nextInt();
// keep them in a loop until they enter a valid number
while (number < 0 || number > 100) {
System.out.println("Please enter a valid number: ");
number = scan.nextInt();
}
// after they entered a valid number, add it to the series
minimum = number;
total += number;
for(int i = 2; i < 11; i++) {
System.out.println("Please enter integer " + i + ":");
number = scan.nextInt();
// keep them in a loop until they enter a valid number
while (number < 0 || number > 100) {
System.out.println("Please enter a valid number: ");
number = scan.nextInt();
}
// after they entered a valid number, add it to the series
total += number;
if(number<minimum)
minimum = number;
if(number>maximum)
maximum = number;
}

problem:
if(number<0 || number >100)
It will return false when number is 100 or 0 thus accepting it and executing you else block.
Is 100>100 answer false because they are equal, not greater than the other
solution:
if(number<1 || number >99)
EDit:
public static void main(String[]args){
Scanner scan = new Scanner(System.in );
int number = 0;
double total = 0;
int minimum = 0;
int maximum = 0;
System.out.println("Please enter the first integer: ");
number = scan.nextInt();
if(number>1 && number <99)
{
minimum=number;
total += number;
}
for(int i = 2; i<11; i++){
if(number<1 || number >99){
System.out.println("Please enter a valid number: ");
number = scan.nextInt();
i--;
}
else{
System.out.println("Please enter integer " + i + ":");
number = scan.nextInt();
total += number;
if(number>1 && number <99)
{
if(number<minimum)
minimum = number;
if(number>maximum)
maximum = number;
}
}
}
DecimalFormat oneDecimalPlace = new DecimalFormat("##.#");
System.out.println("The minimum is: " + minimum);
System.out.println("The maximum is: " + maximum);
System.out.println("The average is: " + oneDecimalPlace.format((total) / 10.0 ));
}

Here is an Example.Exceptions are not handled so put a Try-catch to String to Integer Conversion If you want.
import java.util.Scanner;
import java.text.DecimalFormat;
public class Numbers{
public static void main(String x[]){
Scanner scn=new Scanner(System.in);
int Total=0,Max=0,Min=Integer.MAX_VALUE;
for(int i=0;i<10;){
System.out.print("Enter Number :");
int NumberOne=Integer.parseInt(scn.nextLine());//Put a Try catch If needed
if(NumberOne>0&&NumberOne<100){
Total+=NumberOne;
Max=(Max>NumberOne)?Max:NumberOne;
Min=(Min<NumberOne)?Min:NumberOne;
i++;
}else{
System.out.print("Number Invalid");
}
}
DecimalFormat oneDecimalPlace = new DecimalFormat("##.#");
System.out.println("The minimum is: " + Min);
System.out.println("The maximum is: " + Max);
System.out.println("The average is: " + oneDecimalPlace.format((Total) / 10.0 ));
}
}

infinite loop when asking for number

Hi all thanks for taking the time, I am continuosly getting an infinate loop when i am inserting the variable m could anyone please take a look thanks.
public static void main program7_2(String args [])
{
Scanner sc = new Scanner (System.in);
System.out.println("Please enter the first number: ");
int n = sc.nextInt();
while((n%2)== 0)
{
System.out.println("The number you entered is incorrect please enter an odd number:");
n = sc.nextInt();
}
System.out.println("Please enter the second number: ");
int m = sc.nextInt();
while((m%2)== 0)
{
System.out.println("The number you entered is incorrect please enter an odd number:");
m = sc.nextInt();
}
int sum =0;
for (int i = n; n<=m; i++)
{
if ((i%2) != 0)
sum = sum + i;
}
System.out.println("Sum of the numbers between "+n+ " and " +m+": " + sum);
}
The problem of the program is to enter 2 odd numbers and get the sum of the odd numbers in between
Thanks and regards

Instead of n<=m in your for loop use i<=m since you are using i as your counter and not n

This is the error :
for (int i = n; n<=m; i++) /* terminating condition "n<=m" is never met here */
{
if ((i%2) != 0)
sum = sum + i;
}
Why : this loop increments i but terminating condition is n<=m which is never met....so either do i<n Or i<m which ever suits you for terminating the condition!!

if u want to get the sum of nubers between those two use
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.println("Please enter the first number: ");
int n = sc.nextInt();
while ((n % 2) == 0) {
System.out.println("The number you entered is incorrect please enter an odd number:");
n = sc.nextInt();
}
System.out.println("Please enter the second number: ");
int m = sc.nextInt();
while ((m % 2) == 0) {
System.out.println("The number you entered is incorrect please enter an odd number:");
m = sc.nextInt();
}
int sum= 0;
for (int i = n; i <= m; i++) {
sum = sum + i;
}
System.out.println("Sum of the numbers between " + n + " and " + m + ": " + sum);
}
}