Develop Reference

Why can I not do sum of a and b?

import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter first number");
int a = sc.nextInt();
boolean aValid = sc.hasNextInt();
System.out.println(aValid);
System.out.println("Enter Second number");
int b = sc.nextInt();
boolean bValid = sc.hasNextInt();
System.out.println(bValid);
if(aValid && bValid){
System.out.println("Sum of number is "+(a+b));
}
else{
System.out.println("Enter integer number");
}
}
}
I try to get input of a and b and validate that a and b are integers. But it takes three input. It gives the sum of the first two numbers and gives the validity of the last two.

you need to place check integer statements before taking input
boolean aValid = sc.hasNextInt();
int a = sc.nextInt();
boolean bValid = sc.hasNextInt();
int b = sc.nextInt();

Running this code makes the error fairly obvious. Some additional debug statements, running the code in debug or testing would also make it clear.
Scanner.nextInt() will throw an exception if it gets a non integer.
Scanner.hasNextInt() on the other hand returns a boolean value to warn you in advance whether it has an integer or not - it does not take the value from the Scanner.
This code has a couple of tiny corrections that will achieve the outcome you stated.
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
int a = 0;
int b = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter first number");
boolean aValid = sc.hasNextInt();
if (aValid) {
a = sc.nextInt();
} else {
sc.next(); //Discard the non-integer input.fr
}
System.out.println(aValid);
System.out.println("Enter Second number");
boolean bValid = sc.hasNextInt();
if (bValid) {
b = sc.nextInt();
}
System.out.println(bValid);
if (aValid && bValid) {
System.out.println("Sum of number is " + (a + b));
} else {
System.out.println("Enter integer numbers only");
}
}
}

import java.util.*;
public class Main {
public static void main(String[] args) {
int a = 0;
int b = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter first number");
boolean aValid = sc.hasNextInt();
if (aValid) {
a = sc.nextInt();
}
System.out.println(aValid);
System.out.println("Enter Second number");
boolean bValid = sc.hasNextInt();
if (bValid) {
b = sc.nextInt();
}
System.out.println(bValid);
if (aValid && bValid) {
System.out.println("Sum of number is " + (a + b));
} else {
System.out.println("Enter integer numbers only");
}
}
}

Reading a series of numbers from the user until -1 is inputted, Java

I am trying to write a program to read a series of numbers from the user until -1 is entered. It should then print the average (with decimals) of those numbers (not including the -1). This is what I have so far, but it does not seem to work properly whenever I input -1. This is what I have thus far:
import java.util.Scanner;
import java.util.*;
public class Tute1
{
public static void main (String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter how many numbers you want: ");
int numb = sc.nextInt();
int i =0;
int total =0;
while (i <= numb) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter an integer ");
int myChoice=scan.nextInt();
total=total+myChoice;
i=i+1;
if(myChoice == -1) {
System.out.println("The average is "+ (total+1)/numb);
break;
}
}
System.out.println("The average is "+ total/numb);
}
}

Your code seems a bit odd. Here is how I would do it
import java.util.Scanner;
import java.util.*;
public class Tute1 {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int i = 0;
int total = 0;
while (true) {
System.out.println("Enter an integer ");
int myChoice = scan.nextInt();
if (myChoice != -1) {
total = total + myChoice;
i += 1;
} else {
break;
}
}
float average = total / i;
System.out.println("The average is " + average);
}
Hope this helps. You can add try-catch and stuff to make it so that user does not exploit this

Few things:
first of all you dont need to create a new scanner as your code inside the while loop. Its because the while loop is inside you function scope so every thing you declare on you function the while loop knows about. (It does not work the other way around)
second your breaking condition should be inside the while loop the if with break is redundant and unnecessary.
third thing you should get rid of numb as its doing nithung
import java.util.Scanner;
import java.util.*;
public class Tute1 {
public static void main (String[] args) {
Scanner sc = new Scanner(System.in);
int numb = sc.nextInt();
int i =0;
int total =0;
while (numb != -1)
{
total=total+numb;
i=i+1;
int numb = sc.nextInt()
}
System.out.println("The average is "+ total/i);
}
}
I think this solution is smaller and more elegant

Using a for loop to read ONLY 5 numbers and average them. JAVA

Really having issues with this program I'm making. I've searched this site and a few others, although have yet to find a solution. It may look like I'm just soliciting help but I truly am stuck. I am to make a program that reads in 5 numbers from the user and average those numbers. My extent of knowledge of Java is the Scanner class and for loops, yet haven't used while loops yet. Here is the very poorly written code:
public class Average5
{
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
int num;
System.out.print("Please enter a number: ");
num = sc.nextInt();
for(int num1 = 0; num1 <= num; num1++)
{
System.out.print("Please enter a number: ");
num = sc.nextInt();
}
I honestly have no clue what to do. More or less self taught.

public class Average5 {
public static void main(String args[]) {
int numlenngth = 5;
double total = 0;
Scanner sc = new Scanner(System.in);
for (int num1 = 0; num1 < numlenngth; num1++) {
System.out.print("Please enter a number: ");
total += sc.nextInt();
}
System.out.println("Average : " + (total / numlenngth));
}
}
output >>
Please enter a number: 1
Please enter a number: 1
Please enter a number: 1
Please enter a number: 1
Please enter a number: 2
Average : 1.2

For calculating exact average, you need to take double(sum) instead of int and add(sum) everytime with the user value.
public class Average5
{
public static void main(String args[]){
Scanner sc = new Scanner(System.in);
System.out.print("Please enter how many numbers you want to enter for calculating average: ");
int totalCount = sc.nextInt();
double sum=0;
for(int i= 0; i<totalCount; i++)
{
System.out.print("Please enter a number: ");
sum += sc.nextDouble();
}
System.out.println("Average of number is"+(sum/totalCount));
}

This is almost the same as the others posted, but it is limited to entering only 5 numbers and it takes care of possibly resulting floating number in the final division:
import java.util.Scanner;
public class Average5 {
private static final int TOTAL = 5;
public static void main(final String[] args) {
final Scanner scanner = new Scanner(System.in);
double sum = 0;
System.out.format("You have to enter %d numbers now.\n", TOTAL);
for (int cnt = 1; cnt <= TOTAL; cnt++) {
System.out.format("Please enter number %d of %d: ", cnt, TOTAL);
sum += scanner.nextInt();
}
System.out.format("The average is %f.\n", sum / TOTAL);
scanner.close();
}
}

Here you can use the array to store the numbers:
public class Average5 {
private static final int MAX = 5;
public static void main(String[] args) {
int[] numbers = new int[MAX];
Scanner sc = new Scanner(System.in);
for(int i = 0; i < MAX; i++) {
System.out.println("Please type the number");
numbers[i] = sc.nextInt();
}
float average = getAverage(numbers);
System.out.println("The average of the five numbers: " + average);
}
public static float getAverage(int[] arg0) {
int sum = 0;
float Ret = 0.0f;
if(arg0 != null) {
for(int i = 0; i < MAX; i++) {
sum += arg0[i];
Ret = sum / MAX;
}
return Ret;
}
}
This is not the only way to slove this problem.

int num = 0;
float total = 0f;
Scanner sc = new Scanner(System.in);
System.out.print("Please enter a number: ");
num = sc.nextInt();
for(int num1 = 0; num1 <= num; num1++)
{
System.out.print("Please enter a number: ");
total += sc.nextInt();
}
System.out.println("Average : "+(total/num));

Program that reads num and prints from 1 to num

i need help in logic, i need the program to read an integer from user and then prints all the integers from 1 to num1. here's what i got :
import java.util.Scanner;
public class test
{
public static void main(String []args)
{
Scanner scan = new Scanner(System.in);
int num1;
int num2;
System.out.println("Enter any number:");
num1 = scan.nextInt();
while (num1<=num2) {
System.out.println(num+1);
}
}
}

Try this out:
import java.util.Scanner;
class test {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int number;
System.out.println("Enter any number:");
// Note : The below statement will fail if user does not enter integer value
number = scan.nextInt();
// You can use while loop as well but for loop provides cleaner approach for iteration
for (int i = 1; i <= number; i++) {
// Print numbers sequentially from 1 to number
System.out.println(i);
}
}
}

Program that reads num and prints from 1 to num
Try,
System.out.println("Enter any number:");
num1 = scan.nextInt();
int i=1;
while (i<=num1) {
System.out.println(i);
i++;
}

do like this
int num1=0;
int num2=0;
System.out.println("Enter any number:");
num1 = scan.nextInt();
while (num2 <= num1) {
System.out.println(num2);
num2++;
}

thanks alot guys! its been couple of years since last i coded a java program so im a little rusty! here's my final code :
import java.util.Scanner;
public class test
{
public static void main (String[] args)
{
Scanner scan = new Scanner(System.in);
int num;
int a=1;
System.out.println("Enter any number:");
num=scan.nextInt();
while (a<=num)
{
System.out.println(a);
a++;}
}}

Create a java program that prompt the user for a positive number and then displays each digit in reverse order on a separate line

import java.util.Scanner;
class Digitsdisplay {
public static void main(String args[]){
Scanner input = new Scanner(System.in);
System.out.println("Please enter a value: ");
int value = input.nextInt();
int total = 0;
String digit = "" + value;
System.out.print("");
for (int i = 0; i < digit.length(); i++) {
int myInt = Integer.parseInt(digit.substring(i, i + 1));
System.out.println(myInt);
total += myInt;
}
}
}
output:
Please enter a value:
789
7
8
9
How do I reverse the output? For example, when I enter the number 123, it would display 321 with each digit on a new line.

If the user is inputting values in base 10, you could instead use the modulo operator along with integer division to grab the rightmost values successively in a while loop as so:
import java.util.Scanner;
public class Digitsdisplay {
public static void main(String args[]){
Scanner input = new Scanner(System.in);
System.out.println("Please enter a value: ");
int value = input.nextInt();
int quotient = value;
int remainder = 0;
while(quotient != 0){
remainder = quotient%10;
quotient = quotient/10;
System.out.print(remainder);
}
}
}
This might be a better method that attempting to convert the int to a string and then looping through the string character by character.

Loop you printing for loop in the reverse direction:
import java.util.Scanner;
class Digitsdisplay {
public static void main(String args[]){
Scanner input = new Scanner(System.in);
System.out.println("Please enter a value: ");
int value = input.nextInt();
int total = 0;
String digit = "" + value;
System.out.print("");
for (int i = digit.length()-1; i >= 0; i--) {
int myInt = Integer.parseInt(digit.substring(i, i + 1));
System.out.println(myInt);
total += myInt;
}
}
}
Edit: No reason to reverse the string itself, ie. using a Stringbuilder like the other answers say. This just adds to the runtime.

import java.util.*;
public class Francis {
public static void main(String[] args) {
Scanner input= new Scanner (System.in);
System.out.println("Please enter a value: ");
int value = input.nextInt();
int total = 0;
String digit = "" + value;
System.out.print("");
for (int i = 0; i < digit.length(); i++) {
int myInt = Integer.parseInt(digit.substring(i, i + 1));
System.out.println(myInt);
total += myInt;
}
}
}

Simply reverse the string before looping through it
digit = new StringBuilder(digit).reverse().toString();