Develop Reference

How can I avoid my loop to take the previous answer of the user?

I am making a program that will take a user's input on how many numbers he wants and determine the highest number between the given. After that the user will be prompt with a Yes or no question. If the user decides to say yes, the program will loop again and if not, the program will end. Now my question is why does it take the highest number from the previous run?
import java.util.Scanner;
public class IT_VILLAFLOR_Lab1_Prog2
{
public static void main(String[] Args){
int num=1,num2,Largest=0,max;
char YN;
Scanner sc = new Scanner(System.in);
System.out.print("Enter the Max Number = ");
max = sc.nextInt();
for(num=1; num<=max; num++)
{
System.out.print("Enter Number " + num + ": ");
num2 = sc.nextInt();
if(Largest<num2)
{
Largest=num2;
}
else if(num==max)
{
System.out.println("The Biggest number is " + Largest );
System.out.print( "Do you want to try again? Y/N ");
YN = sc.next().charAt(0);
if(YN =='Y'|| YN =='y')
{
num=0;
System.out.print('\f');
System.out.print("Enter the Max Number " );
max = sc.nextInt();
}
else
{
System.exit(0);
}
}
}
}
}

If the user wants to continue, you are resetting num to 0. Along with this, Largest also needs to be reset to 0.
num=0;
Largest=0; //new code
By the way, you need to change the line else if(num==max) to if(num==max) . Try the test case with max of 2 and values as 12 ,23.

Java Sum of numbers until string is entered

i've just started java programming and was wondering on how to approach or solve this problem i'm faced with.
I have to write a program that asks a user for a number and continually sums the numbers inputted and print the result.
This program stops when the user enters "END"
I just can't seem to think of a solution to this problem, any help or guidance throughout this problem would be much appreciated and would really help me understand problems like this. This is the best i could do
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
while (true) {
System.out.print("Enter a number: ");
int x = scan.nextInt();
System.out.print("Enter a number: ");
int y = scan.nextInt();
int sum = x + y;
System.out.println("Sum is now: " + sum);
}
}
}
The output is supposed to look like this:
Enter a number: 5
Sum is now: 5
Enter a number: 10
Sum is now: 15
Enter a number: END

One solution would be to not use the Scanner#nextInt() method at all but instead utilize the Scanner#nextLine() method and confirm the entry of the numerical entry with the String#matches() method along with a small Regular Expression (RegEx) of "\d+". This expression checks to see if the entire string contains nothing but numerical digits. If it does then the matches() method returns true otherwise it returns false.
Scanner scan = new Scanner(System.in);
int sum = 0;
String val = "";
while (val.equals("")) {
System.out.print("Enter a number (END to quit): ");
val = scan.nextLine();
// Was the word 'end' in any letter case supplied?
if (val.equalsIgnoreCase("end")) {
// Yes, so break out of loop.
break;
}
// Was a string representation of a
// integer numerical value supplied?
else if (val.matches("\\-?\\+?\\d+")) {
// Yes, convert the string to integer and sum it.
sum += Integer.parseInt(val);
System.out.println("Sum is now: " + sum); // Display Sum
}
// No, inform User of Invalid entry
else {
System.err.println("Invalid number supplied! Try again...");
}
val = ""; // Clear val to continue looping
}
// Broken out of loop with the entry of 'End"
System.out.println("Application ENDED");
EDIT: Based on Comment:
Since since an integer can be signed (ie: -20) or unsigned (ie: 20) and the fact that an Integer can be prefixed with a + (ie: +20) which is the same as unsigned 20, the code snippet above takes this into consideration.

Do it like this:
public static void main(String[] args) throws Exception {
int sum = 0;
Scanner scan = new Scanner(System.in);
while (scan.hasNext()) {
System.out.print("Enter a number: ");
if (scan.hasNextInt())
sum += scan.nextInt();
else
break;
System.out.println("Sum is now: " + sum);
}
System.out.print("END");
}
This will end if the input is not a number (int).
As pointed out in the comments, if you want the program to stop when the user specifically enters "END", change the else-statement to:
else if (scanner.next().equals("END"))
break;

Why is my very simple while loop repeating one extra time?

Here is my while loop. The program sums up integers until a negative number is input. At that point the loop should break and it should print "Goodbye". However it is adding the negative number each time before it says goodbye. Im not sure what is going wrong here. Please help?!
import java.util.Scanner;
public class While {
public static void main(String[] args)
{
int input = 5;
int sum = 0;
while(input >= 0)
{
System.out.println("Please enter a positive integer: ");
Scanner in = new Scanner (System.in);
input = in.nextInt();
sum = sum + input;
System.out.println("Running total: " + sum );
}
System.out.println("Goodbye!" );
}
Test:
Please enter a positive integer:
5
Running total: 5
Please enter a positive integer:
10
Running total: 15
Please enter a positive integer:
-1
Running total: 14
Goodbye!
I do not want to get the return value of 14, it should simply say Goodbye!

You need to use the break keyword. Your loop will always finish so the check on the while only happens after you've added the negative number. You could change to this:
while(true)
{
System.out.println("Please enter a positive integer: ");
Scanner in = new Scanner (System.in);
input = in.nextInt();
if(input <0){
break;
}
sum = sum + input;
System.out.println("Running total: " + sum );
}
Or this:
while(input >= 0)
{
System.out.println("Please enter a positive integer: ");
Scanner in = new Scanner (System.in);
input = in.nextInt();
if(input <0){
break;
sum = sum + input;
System.out.println("Running total: " + sum );
}
}
Or to avoid if statements entirely if needed (though that isn't the point of loops):
while(input >= 0)
{
sum = sum + input;
System.out.println("Please enter a positive integer: ");
Scanner in = new Scanner (System.in);
input = in.nextInt();
System.out.println("Running total: " + sum );
}

Here was my solution:
while(input >= 0)
{
sum = sum + input;
System.out.println("Running total: " + sum );
System.out.println("Please enter a positive integer: ");
Scanner in = new Scanner (System.in);
input = in.nextInt();
}
System.out.println("Goodbye!" );
}
by calculating the sum at initialization and before the first integer is entered. It appears to work the way I want now. Thanks for your help.

I am trying to get user input until user enter 0 and then show maximum value among them in JAVA

I am a beginner to java and don't know to write a program using loops that prompt the user to enter a number till user does does not enter 0.
When user enter 0 then system should display MAX number among user input
QUE 2
Write a program to ask the user to enter a sequence of numbers (double type). The numbers are separated by the return key (and give a prompt for each enter). The user ends the sequence by entering a 0. Then output the maximum number of all the entered numbers. Here is an example (the part in italic is the user’s input): Please enter a sequence of numbers, separated by return, and then end this sequence with a 0 at last: 25
Next number: 35.6
Next number: 112.112
Next number: 0
The maximum among your enters is 112.112
import java.util.Scanner;
public class Q3
{
public static void main(String[] args[])
{
double n;
// double i;
double MAX=0;
System.out.println("Please Enter the number: ");
Scanner Kb = new Scanner(System.in);
n = Kb.nextDouble();
if(n>0){
System.out.println("Please Enter the number: ");
n = Kb.nextDouble();
return;
}
else if(n==0) {
if (MAX>0){
MAX=n;
return ;
}
}
return;
}
}

Keep track of the max and each time a user inputs a number check if it is greater than that max
import java.util.Scanner;
public class Q3 {
public static void main(String... args) {
double max = 0;
System.out.println("Please enter the number: ");
Scanner kb = new Scanner(System.in);
double number = kb.nextDouble();
while (number != 0) {
if (max < number) {
max = number;
}
number = kb.nextDouble();
}
System.out.print("The max is " + max);
}
}
Since zero is the terminal character then negative input can be essentially ignored and the initial value of max as zero is acceptable.
Note that nextDouble can throw an InputMismatchException if the user decides to give you input that can not be parsed to a double.

using Collections.max ,
List<Double> doubleList = new ArrayList<>();
System.out.println("enter a number :");
Scanner kb = new Scanner(System.in);
while (kb.hasNext() ) {
double input = kb.nextDouble();
if(input == 0){
break;
}
doubleList.add(input);
}
System.out.println("Max Value Entered : " + Collections.max(doubleList));

Scanner sc = new Scanner(System.in);
double max = 0;
while(true){
double number = sc.nextDouble();
if(max<number){
max = number;
}
else if(number==0){
break;
}
}
System.out.print(max);

Output sum of even numbers between two integers

I am working on a simple JAVA question in one of my college courses. I am stumped on this one program. I will display what I have so far and give the question I have to answer. I also looked at a similar question on StackOverflow, BUT it isn't the same problem so it DIDN'T help. The program I need to write is:
Write a program that uses 'while' loops to perform the following steps:
a.) Prompt the user to input two integers: 'firstNum' and 'secondNum' (firstNum must be less than secondNum)
b.) Output all the odd numbers between 'firstNum' and 'secondNum' inclusive.
c.) Output the sum of all the even numbers between 'firstNum' and 'secondNum' inclusive.
This is what I have so far... (I still need to calculate the even numbers and sum them up)
//import classes
import java.util.*;
public class chapter5no9
{
static Scanner console = new Scanner(System.in);
public static void main(String[] args)
{
//Part A
int firstNum;
int secondNum;
int sumEven;
System.out.println("Please enter an integer: ");
firstNum = console.nextInt();
System.out.println("Please enter another integer less than the first integer: ");
secondNum = console.nextInt();
//Part B
if (firstNum < secondNum)
{
System.out.print("Your second number is greater than the first. So Please re-enter: ");
secondNum = console.nextInt();
}
else
{
System.out.print("Odd Numbers: ");
firstNum++;
while (firstNum > secondNum)
{
if (secondNum % 2 != 0)
{
System.out.print(" " + secondNum);
}
secondNum++;
}
System.out.println();
System.out.print("Sum of Even Numbers: ");
firstNum++;
while (firstNum > secondNum)
{
if (secondNum % 2 != 0)
{
System.out.print(" " + secondNum);
}
secondNum++;
}
}
}
}

I created the loopCounter variable to handle the required iterations without changing the values inputted by the user. The following changes have been made to your code.
Part A: added a while loop to validate user input. Also changed logic in if statement.
Part B: used one loop to print odd numbers and total even numbers
//Part A
int firstNum;
int secondNum;
int sumEven=0;
System.out.println("Please enter an integer: ");
firstNum = input.nextInt();
System.out.println("Please enter another integer less than the first integer: ");
secondNum = input.nextInt();
//Part B
//validate input in a loop
while(true)
{
if (firstNum > secondNum)
{
System.out.print("Your second number is larger than the first. So Please re-enter: ");
secondNum = input.nextInt();
}
else
{
break;
}
}
System.out.print("Odd Numbers: ");
int loopCounter=firstNum;
while(loopCounter<secondNum)
{
if (loopCounter%2!=0)
{
System.out.print(" " + loopCounter);
}//end if
else
{
sumEven+=loopCounter;
}//end else
loopCounter++;
}
System.out.println();
System.out.print("Sum of Even Numbers: ");
System.out.print(sumEven);
}

I would separate the two concerns of checking input and calculating the result. Here's how I would calculate it:
int sum = IntStream.rangeClosed(firstNum, secondNum).filter(i -> i % 2 == 0).sum();

The issue is in your logic. You have this if statement:
if (firstNum < secondNum)
{
System.out.print("Your second number is greater than the first. So Please re-enter: ");
secondNum = console.nextInt();
}
Which checks if the second number is greater than the first (which you want it to be) and then asks them to re-enter. You want to check if (secondNum < firstNum). You will need to reverse all your while and if statements that compare secondNum to firstNum.
Then you have this if (secondNum % 2 != 0) to check for odd numbers, which is correct, but you copy-pasted it to check for even numbers, which won't work, you will need to change that as well.
Then, you are outputting all the even integers inside your loop, when really you want to be adding it to an evenSum variable, and outputting that at the end of the loop:
System.out.println("The sum of all even integers is: " + evenSum);
That should be enough to help you, I'm not going to write your homework for you, that's not what we do here.

package hello.world;
import java.util.Scanner;
public class HelloWorld {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int number ;
int X = 0;
System.out.print("enter a number plz : ");
number = sc.nextInt();
while (X <= number){
System.out.println(X);
X ++;
}
}
}