I am new to Java and I came up to this error in my program where I can't add the elements in an array of BigDecimal elements. I successfully made it with Integer and Double types but when I change the type to BigDecimal, it won't work at all.
import java.math.*;
import java.util.*;
public class AddBigRealNumbers {
public static void main(String[] args) {
try{
Scanner von = new Scanner(System.in);
System.out.println("Enter the number of figures to be added:");
int numfig;
numfig = von.nextInt();
BigDecimal []nums = new BigDecimal[numfig];
System.out.println("Enter the elements:");
for(int i=0; i<numfig;i++){
nums[i]=von.nextBigDecimal();
}
System.out.println("The elements are: ");
for(int i=0; i<numfig;i++){
System.out.println(nums[i]);
}
BigDecimal sum=BigDecimal.ZERO;
for (BigDecimal i : nums)
sum += i;
System.out.println("The sume of these numbers is:"+sum);
}
catch(Exception e){
System.out.println("Your exception is:" +e);
}
}
}
You can't add BigDecimal with +, you have to use its add() function. It is also immutable, so using the same BigDecimal sum for the whole addition won't work.
BigDecimal isn't just another class for numbers like Integer and Double are.
Because BigDecimal is immutable as LisaMM pointed out, you will need to increment your sum like so:
for (BigDecimal i : nums) {
sum = sum.add(i);
}
...
sum.add(i); <-- this wont't work
Instead we need to reassign a new BigDecimal to sum using its current value incremented by i.
BigDecimal sum = null;
for (int i = 0; i < lengthOfArray; i++) {
if (sum == null) {
sum = data[i];
} else {
sum = sum.add(data[i]);
}
}
Related
I'm supposed to use two methods to hold arrays, then with the two arrays determine win % of the rockets, average margin of score difference for the games lost by Houston Rockets, and the lowest Houston Rockets’ score and the corresponding game number. I primarily need help with the first one, and I can get the other tasks. I just dont know how to pass arrays from methods very well. Any help would be useful, THanks!
import java.util.Scanner;
public class MorenoJonathonRocketsStatistics
{
public static void main(String[] args)
{
System.out.println("enter rockets game scores");
int[] rockets = rocketsScore();
System.out.println("enter opponents scores");
int[] opponents = opponentsScore();
int per = percent();
System.out.println("game win percent"+per+" %");
}
public static int[] rocketsScore()
{
Scanner sc = new Scanner(System.in);
int[] rocketsScore = new int[8];
for(int i=0;i<rocketsScore.length;i++)
{
rocketsScore[i] = sc.nextInt();
}
return rocketsScore;
}
public static int[] opponentsScore()
{
Scanner sc = new Scanner(System.in);
int[] opponentsScore = new int[8];
for(int i=0;i<opponentsScore.length;i++)
{
opponentsScore[i] = sc.nextInt();
}
return opponentsScore;
}
public static int percent(int[] array, int[] array2)
{
int[] rock = rocketsScore.length();
int[] opp = opponentsScore.length();
double percent=0;
int w=0, l=0;
for(int i=0; i<rocketsScore.length;i++)
{
if(rocketsScore[i]>opponentsScore[i])
{
w++;
}
else{
l++;
}
}
percent = w/l;
return percent;
}
}
To pass array in methods, you don't need to put any brackets beside the variable that is holding the array. So, you may want to do it like below:
int per = percent(rockets, opponents);
I work on a trainigs code to compare the distance of an unspecific number of points from the zero point.
The error appears when i want to write the input point values into the Point array and i don't know how to handle it:
points[i].setLocation(x,y);
Error says: Exception in thread "main" java.lang.NullPointerException
at minDis.minDis.main(minDis.java:59)
I would be thankful for any advices.
import java.awt.Point;
import java.util.Scanner;
public class minDis {
private static final Point Point = null;
static double dis(Point p){
double dis= Math.sqrt(p.x*p.x+p.y*p.y);
return dis;
}
static double minDist(Point[] points, int anz){
double minimum= dis(points[0]);
for(int z=0; z<anz; z++){
if (dis(points[z]) < minimum)
minimum=dis(points[z]);
}
return minimum;
}
static double minDistPoint(Point[] points, int anz){
double minimum= dis(points[0]);
int DistPoint = 0;
for(int z=0; z<anz; z++){
if (dis(points[z]) < minimum)
minimum=dis(points[z]);
DistPoint=z;
}
return DistPoint;
}
public static void main(String[] args) {
Point points[]=null;
Scanner scan= new Scanner(System.in);
System.out.println("How many Points do you want to compare?");
int anz= scan.nextInt();
for(int i=0; i<anz; i++){
System.out.println("Type in Point "+anz);
System.out.println("X: ");
int x= scan.nextInt();
System.out.println("Y: ");
int y= scan.nextInt();
**points[i].setLocation(x,y);**
}
scan.close();
System.out.println("It is Point "+minDistPoint(points, anz)+" with a distance of "+ minDist(points, anz));
}
}
In your code snippet, you are not allocating memory for the Pointer Object array. That's why you are getting NullPointerException. Therefore, you need to allocate memory to the array of Point objects in your code.
But, remember when you create a array of objects like this,
Object[] arr = new Object[10];
Here you are just creating 10 Object References. Now, to do any operations with individual array elements, you need to allocate memory to each object also, For Example,
arr[i] = new Object();
So, use the following snippet as the corrected version for your code.
public static void main(String[] args) {
Point[] points;
Scanner scan= new Scanner(System.in);
System.out.println("How many Points do you want to compare?");
int anz= scan.nextInt();
points = new Point[anz];
for(int i=0; i<anz; i++) {
points[i] = new Point();
System.out.println("Type in Point "+anz);
System.out.println("X: ");
int x= scan.nextInt();
System.out.println("Y: ");
int y= scan.nextInt();
points[i].setLocation(x,y);
}
scan.close();
System.out.println("It is Point "+ minDistPoint(points, anz)+" with a distance of "+ minDist(points, anz));
}
I have to find the LCM of two integers using the prime factors method and function calls.
I'm up to making a function to find the prime factorization of the first number, but I'm getting errors at int x = first_number; and with System.out.print(primeFactorization).
This is my code so far:
import java.util.Scanner;
public class lcm {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
int first_number;
int second_number;
System.out.print("Enter an integer: ");
first_number = reader.nextInt();
System.out.print("Enter another integer: ");
second_number = reader.nextInt();
}
public static int primeFactorization(int[] pfArray) {
int counter = 0;
pfArray = new int[10]; //created array in memory
int x = first_number;
for(int i=2;i<=x;i++){
while(x%i==0){
x=x/i;
pfArray[counter] = i;
++counter;
}
}
for(int i=0;i<counter;i++){
System.out.println(pfArray[i]);
}
}
System.out.println(primeFactorization);
}
I am just starting to learn Java, so please answer in very basic terms!
Thanks so much!
The variable first_number is declared in the first method and so cannot be used within the second method unless you pass it in as a parameter.
The only thing called primeFactorisation is the method. System.out.println requires an object (a variable) as its input. So you can't do it like that.
I'm practicing learning Java and I found this exercise online to input a long integer (ex 2827) and then calculate how many different digits there is in the integer (2,8 and 7) = 3 in this case.
I'm considering using a for loop and then with subString, comparing if the number equals each others and they (tutorial) suggest that I should use an array "used" to register which numbers appear, nonetheless
This is what I've got so far:
import java.util.Scanner;
public class UniqueInteger {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
boolean[] used = new boolean[10];
int uniqueNbr = 0;
System.out.print("Input an integer: ");
String nbrString = String.valueOf(scan.nextLong());
for (int i = 0; i < nbrString.length(); i++) {
String bigI = String.valueOf(i);
if(nbrString.substring(i,(i+1)).equals(bigI)){
uniqueNbr++;
}
}
System.out.println("Amount of unique digits: " + uniqueNbr);
}
}
My problem is now that this code does not work, and I'm not sure I'm taking the right approach here. I've also not found a reason or purpose to include the boolean array "used".
What's wrong with my code?
How do I in a smart way use the boolean array and make my code more efficient?
You need to check if the current number in the string has been used (using your boolean array). If it hasn't been used, set used[num] to true and increment uniqueNbr.
import java.util.Scanner;
public class UniqueInteger {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
boolean[] used = new boolean[10];
int uniqueNbr = 0;
System.out.print("Input an integer: ");
String nbrString = String.valueOf(scan.nextLong());
for (int i = 0; i < nbrString.length(); i++) {
int num = Character.getNumericValue(nbrString.charAt(i));
if(!used[num]) {
uniqueNbr++;
used[num] = true;
}
}
System.out.println("Amount of unique digits: " + uniqueNbr);
}
}
Is it possible to sort (ascending) the randomly generated integer array for the following code? If, so how?
import java.util.Random;
public class RandomArraySorter {
public static void main(String args[]){
Random random = new Random();
int array[] = new int[10];
//number of integer spaces within the array:
for(int i = 0; i < 10; i++){
//random numbers from 1 to 100:
array[i] = random.nextInt(100) + 1;
System.out.print(array[i] + " ");
}
} //end of main
} //end of class
You can sort with:
Arrays.sort(array);