If a user enters a value for
x y and z coordinates, what steps would need to take in order to create a range from -x/y/z to +x/y/z? Is there a function that will give the numbers in that range even though a double is entered?
This is my code so far im not finished yet, I'm not sure if its right. After it gets the x,y,z points and the number of data points the user wants, it will then print the n number of points with random points (x , y, z) x, y, z being anywhere from -x to x etc.
import java.io.*;
public class MultiDimArray
{
public static void main (String [] args) throws IOException
{
BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));// Buffered Reader reads the number inputed
double range;
System.out.println("How many points do you want returned? ");
String numPointsA = myInput.readLine();
int numPoints = Integer.parseInt(numPointsA);
System.out.println("Enter X length: ");
String xlengthA = myInput.readLine();
double xlength = Double.parseDouble(xlengthA);
System.out.println("Enter Y length: ");
String ylengthA = myInput.readLine();
double ylength = Double.parseDouble(ylengthA);
System.out.println("Enter Z length: ");
String zlengthA = myInput.readLine();
double zlength = Double.parseDouble(zlengthA);
int[][][][] dataPoint = new int[3][xlength][ylength][zlength];
for (int i = 0; i < (xlength * 2); i++){
range = (0 -( xlength - i) + 1);
System.out.println(range);
}
for (int i = 0; i < (ylength * 2); i++){
range = (0 -( ylength - i) + 1);
}
for (int i = 0; i < (zlength * 2); i++){
range = (0 -( zlength - i) + 1);
}
}
}
range is infinite if you want to include all fractional numbers otherwise you can do that manually.
for (int i=-x; i<=x; i++)
operate(i, y, z);
another solution for your problem is that you don't generate range.
you just store those values x y and z.
then, when you need to test if a number is in range you can do it easily with if statement.
what I mean that this a wrong way to design your solution. try to get values you want in another way. something like reverse engineering. then you test if those values are in range.
post your problem. then we can help you.
Code that generates numPointsA random numbers between -x and x:
Random random = new Random();
double start = -x;
double end = x;
for (int i=0;i<numPointsA;i++)
{
double ran = random.nextDouble();
double result = start + (ran * (end - start));
System.out.println(result);
}
To get a random number between 0 and n-1, use
Random rand = new Random();
int r = rand.nextInt(n);
Related
I am trying to write a simple mastermind game where a 4 digit number will be randomly selected by the computer and the user inputs a number over and over again until the correct number is found. I am trying to do this by passing the guessed number and the random number to their own separate arrays and then comparing them, position by position to see if they are similar. If two numbers are in the exact same spot
Example:
if guessArray[0] == numsArray[0] then the computer will print a *.
If two numbers are present but not in the exact same spot (eg. you made a guess of 2056 but the actual number is 1203) then one + should be printed. This cycle repeats until the number is guessed.
I've already asked a friend in person what the problem was and he couldn't figure it out. He knows the most code out of my friends so this was my next place to go.
Here is the full project. I did not write the ConvertInt2Array method. I found it on the internet.
import java.util.Scanner;
import java.util.Arrays;
import java.util.Random;
public class Mastermind {
public static Random numGen = new Random();
public static void main(String [] args) {
Scanner Input = new Scanner (System.in);
int x = 0;
int number = 0;
int random = 0;
int guess = 0;
int y = 0;
int numArray[] = new int[4];
int guessArray[] = new int[4];
boolean isGuessed = false;
//Generate Random Number
for(x=0; x<=3; x++) {
int rand = Math.abs(numGen.nextInt());//Get the absolute value
random = (rand % 999 + 1);
numArray[x] = random;
number+=random;
}
while(isGuessed == false){
System.out.println("Guess a four digit random number");
guess = Input.nextInt();
guessArray = convertInt2Array(guess);
for(y=0; y<=3; y++) {
if(numArray[y] == guessArray[y]) {
System.out.print("*");
}
else if(Arrays.equals(numArray, y, y, guessArray, 0, guessArray.length) == true) {
System.out.print("+");
}
else {
}
if(guess==number) {
isGuessed = true;
}
}
}
System.out.println("You guessed it correctly!");
}
public static int[] convertInt2Array(int guess) {
String temp = Integer.toString(guess);
String temp2;
int temp3;
int [] gArray = new int[temp.length()];
for(int i=0;i<temp.length();i++) {
if (i!=temp.length()) {
temp2 = temp.substring(i, i+1);
} else {
temp2 = temp.substring(i);
}
temp3 = Integer.parseInt(temp2);
gArray[i] = temp3;
}
return gArray;
}
}
There may be more than one issue here, but here's a potential problem:
int rand = Math.abs(numGen.nextInt()); // Get the absolute value
random = (rand % 999 + 1);
This will usually result in random being a three-digit number. You mentioned you want this to be a four-digit number. Random.nextInt() can return any of the possible 232 integer numbers (from -2147483648 to 2147483647). To fix this, use a different Random.nextInt and specify your bounds:
int lowerBound = 1000;
int upperBound = 10000;
random = numGen.nextInt(upperBound - lowerBound) + lowerBound;
Let's break this down: numGen.nextInt(upperBound - lowerBound) evaluates to numGen.nextInt(9000), which will return a number between 0 (inclusive) and 9000 (exclusive), i.e. anything in the range 0-8999. You then add the lower bound of 1000 to ensure that random will be at least 1000 and up to 9999.
See the documentation for Random.nextInt(int bound).
Hopefully this gets you pointed in the right track.
What is wrong with this code? It says cannot convert from String to int, but I have already converted it.
public static void main(String[] args) {
String x = JOptionPane.showInputDialog(null, "Hur många värden haver du?");
int i = Integer.parseInt(x);
for (int y = 0; i >= y; y++) {
String z = JOptionPane.showInputDialog(null, "Skriv in värdet");
int sum = Integer.parseInt(z);
sum = (sum + z);
}
}
No you have converted z to int and store the result in sum so sum is the int value of z but z is still a variable of type String. What you are trying to do here is the same as multiplying sum by two.
But i assum you want to sum all input values, so you can do sum = (sum + Integer.parseInt(z)); and put the declaration of sum outside the loop, otherwise you initialize it on every iteration. Another bug is that if you input x it will iterate x + 1 times because of i >= y. Fixed version below.
String x = JOptionPane.showInputDialog(null, "Hur många värden haver du?");
int i = Integer.parseInt(x);
int sum = 0;
for (int y = 0; i > y; y++)
{
String z = JOptionPane.showInputDialog(null, "Skriv in värdet");
sum = (sum + Integer.parseInt(z));
}
System.out.println(sum);
Input: 3 (number of iterations)
Input: 7
Input: 5
Input: 6
Output: 18
Java don't do automatic conversion between types. So you can't add Strings with numbers and expect it to do math.
What Java does do it auto boxing of primitive types to objects. And it will automatically attempt to call toString() on objects if you use it in a String concatenation.
So as Reimeus wrote. You need to convert the String to a number before you start using it in math
Cannot convert from String to int
sum=(sum+z) // int+string // this was the problem
change your z to int as:
int iz= Integer.parseInt(z);
sum = (sum + iz);
int sum = 0;
for (int y = 0; i >= y; y++) {
try{
String z = JOptionPane.showInputDialog(null, "Skriv in värdet");
sum = (sum + Integer.parseInt(z));
} catch (Exception e){
System.out.println("This was not an Integer: " + z);
}
}
The exception will prevent your program from crashing, but it will not screw up your 'sum'. So you can put an other value again, and go on...
I'm working on a question where i need to find the length of the side given the coordinates of a polygon.
N is the number of rows and 2 is number of columns ( x and y coordinates) and i've collected the coordinates in a multi-dimensional array.
what my idea was to collect the x coordinates in a array say x1 and collect y coordinates in a array say y1. now find the difference between the numbers in the array and perform the distance formula operation. but im not able to proceed any further. im not able to find the length using it as the answer is always short of the actual number. kindly help on how can i find the length of the sides of a given polygon. please find my code below:
import java.util.Scanner;
public class Rope {
public static void main(String[] args) {
int N = 1, R=1;
double AoN=1;
float d=0 , e=0, f=0, h=0, s=0, length=0, g=0;;
Scanner in = new Scanner(System.in);
int[] arr = new int[2];
System.out.println("Enter number of Nails (N) and Radius of Nail (R) seperated by space: ");
for (int i=0;i<arr.length;i++) {
arr[i]=in.nextInt();
}
if (arr[0]>=1 && arr[0]<=100) {
N=arr[0]; // N is the number of rows of the multi-dimensional array and rows is fixed to 2 as coordinates are fixed to x and y so 2.
}
R=arr[1]; // kindly ignore R as it is used for other purpose.
float[ ][ ] arr1 = new float[N][2];
System.out.println("Enter Coordinates separated by spaces: ");
for(int i=0; i<N;i++) {
for (int j=0;j<2;j++) {
arr1[i][j]=in.nextFloat();
//System.out.println(arr1[i][j]);
}
}
float[] x = new float[N];
float[] y = new float[N];
for(int i=0; i<N;i++) {
x[i] = arr1[i][0];
}
for (int j=0;j<N;j++) {
y[j] = arr1[j][1];
}
for (int i=0; i<x.length-1;i++) {
d = (float) (d + (Math.pow((x[i+1] - x[i]),2)));
}
for (int i=0; i<y.length-1;i++) {
e = (float) (e + (Math.pow((y[i+1] - y[i]),2)));
}
g = d+e;
s = (float) Math.sqrt(g);
sysout(s);
in.close();
}
}
because you have a logical glitch in your code. Here if you notice in the following section :
for (int i=0; i<x.length-1;i++) {
d = (float) (d + (Math.pow((x[i+1] - x[i]),2)));
}
for (int i=0; i<y.length-1;i++) {
e = (float) (e + (Math.pow((y[i+1] - y[i]),2)));
}
Lets say,
x1-x2 = X1
x2-x3 = X2
and so on
similarly,
y1-y2 = Y1
y2-y3 = Y2
and so on
now what your code does is it calculates
sqrt(X1*X1 + X2*X2.... +Y1*Y1 + Y2*Y2....)
But what actually it is supposed to do is,
sqrt(Math.pow((X1-X2),2) + Math.pow(Y1-Y2),2)) + sqrt (Math.pow((X2-X3),2) + Math.pow((Y2-Y3), 2) + ...
thus your code generates wrong values.
You should try the following :
for (int i=0; i<x.length-1;i++) {
float temp;
temp = (Math.pow((x[i+1] - x[i]),2)) + (Math.pow((y[i+1] - y[i]),2));
d = (float) (d + sqrt(temp));
}
// for first and last values / coordinates w.r.t distance formula
for (int i=x.length-1; i<x.length;i++) {
float temp;
temp = (float) ((Math.pow((x[i] - x[0]),2)) + (Math.pow((y[i] - y[0]),2)));
d = (float) (d + Math.sqrt(temp));
}
Instead of that above mentioned two lines.
Hope this helps !!!
I am trying to do the famous Monte Carlo simulation to estimate pi for my Java course.
Here is the Simulation:
public class Darts
{
//"throwing" a dart
public static boolean [] dartThrow(int r, int d){
boolean [] booleanArray = new boolean[d];
for(int i = 0; i < d; i++){
double xCoord = Math.random() * 2;
double yCoord = Math.random() * 2;
if((Math.pow(xCoord,2) + Math.pow(yCoord,2)) <= r){
booleanArray[i] = true;
}
else{
booleanArray [i] = false;
}
}
return booleanArray;
}
//calculating pi from throwing results
public static double piEstimater(boolean [] h, int d){
int trueCounter = 0;
for(int i = 0; i < h.length; i++){
if(h[i] == true){
trueCounter++;
}
}
return 4 * ((double)trueCounter / d);
}
//printing results
public static void printer(double [] a){
System.out.println(" Pi Estimation Tool ");
System.out.println("---------------------------");
for(int i = 0; i < a.length; i++){
System.out.print("Trial [" + i + "]: pi = ");
System.out.printf("%6f\n", a[i]);
}
}
public static void main(String[] args){
//variables
Scanner in = new Scanner(System.in);
int radius = 1;
int darts;
int trials;
System.out.println("Enter the number of darts to calculate for: ");
darts = in.nextInt();
System.out.println("Enter the number of trials to calculate for: ");
trials = in.nextInt();
double [] arrayOfEstimates = new double [trials];
int i = 0;
for(double a : arrayOfEstimates){
boolean [] hitCounter = dartThrow(radius, darts);
double piEstimate = piEstimater(hitCounter, darts);
arrayOfEstimates[i] = piEstimate;
i++;
}
printer(arrayOfEstimates);
}
}
I have created code that executes correctly, except for that the results never go above ~ .8. I would like to just assume that this is happening because the random numbers are so low, but if it happens every time something HAS to be wrong, right? Please keep in mind that this code contains about all the Java techniques I know, so I would appreciate it if you kept from including anything more "advanced." Thanks!
The idea of the calculation of PI using the Monte Carlo method is to sample random points in a square, and count the fraction of them that fall within the area of a circle bound by that square. If enough points are uniformly sampled, the fraction would be close to the area of the circle divided by the area of the bounding square :
fraction = PI*r^2/(2r)^2
and therefore
PI = fraction * 4.
Now, since you are sampling only positive coordinates, if we assume that the circle is centered at the origin (0,0), we only sample points within the top-right quarter of the circle and its bounding square, but the equation remains the same.
If your circle has radius r, you should sample coordinates between 0 and r.
Therefore you should change this :
double xCoord = Math.random() * 2;
double yCoord = Math.random() * 2;
To this :
double xCoord = Math.random() * r;
double yCoord = Math.random() * r;
In addition the condition should be ((Math.pow(xCoord,2) + Math.pow(yCoord,2)) <= r*r).
Of course, you can simplify it by eliminating r and assuming the radius is 1.
In that case the condition would be ((Math.pow(xCoord,2) + Math.pow(yCoord,2)) <= 1) and the coordinates would be sampled between 0 and 1.
This is a homework problem
How would I reverse an integer in Java with a for loop? The user will input the integer (I don't know how long it will be) and I need to reverse it. ie: If they enter 12345, my program returns 54321.
Here's the catch, you can't use String, StringBuffer, arrays, or other advanced structures in this problem.
I have a basic idea of what I need to do. My problem is...in the for loop, wouldn't the condition need to be x < the length of the integer (number of digits)? How would I do that without String?
Thanks for any input, and I'll add more information if requested.
EDIT:
Of course, after introspection, I realized I should use another for loop to do this. What I did was create a for loop that will count the digits by dividing by 10:
int input = scan.nextInt();
int n = input;
int a = 0;
for (int x = 0; n > 0; x++){
n = n/10;
a = a + 1;
}
EDIT 2:
This is what I have
int input = scan.nextInt();
int n = input;
int a = 0;
int r = 0;
for (int x = 0; n > 0; x++){
n = n/10;
a = a + 1;
}
for (int y = 0; y < n; y++) {
r = r + input%10;
input = input/10;
}
System.out.println(input);
When I run it, it isn't reversing it, it's only giving me back the numbers. ie: if I put in 1234, it returns 1234. This doesn't make any sense to me, because I'm adding the last digit to of the input to r, so why wouldn't it be 4321?
While your original number is nonzero, take your result, multiply it by 10, and add the remainder from dividing the original by 10.
For example, say your original number is 12345. Start with a result of 0.
Multiply result by 10 and add 5, giving you 5. (original is now 1234.)
Multiply result by 10 and add 4, giving you 54. (original is now 123.)
Multiply result by 10 and add 3, giving you 543. (original = 12.)
Multiply result blah blah 5432. (original = 1.)
Multiply, add, bam. 54321. And 1 / 10, in int math, is zero. We're done.
Your mission, should you choose to accept it, is to implement this in Java. :) (Hint: division and remainder are separate operations in Java. % is the remainder operator, and / is the division operator. Take the remainder separately, then divide the original by 10.)
You will need to use math to access each of the digits. Here's a few hints to get your started:
Use the % mod operator to extract the last digit of the number.
Use the / division operator to remove the last digit of the number.
Stop your loop when you have no more digits in the number.
This might not be the proper way but
public static int reverseMe(int i){
int output;
String ri = i + "";
char[] inputArray = ri.toCharArray();
char[] outputArray = new char[inputArray.length];
for(int m=0;m<inputArray.length;m++){
outputArray[inputArray.length-m-1]=inputArray[m];
}
String result = new String(outputArray);
output = Integer.parseInt(result);
return output;
}
public static void reverse2(int n){
int a;
for(int i = 0; i < n ; i ++){
a = n % 10;
System.out.print(a);
n = n / 10;
if( n < 10){
System.out.print(n);
n = 0;
}
}
}
here is the Answer With Correction of Your Code.
import static java.lang.Math.pow;
import java.util.*;
public class MyClass {
public static void main(String args[]) {
Scanner scan=new Scanner(System.in);
int input = scan.nextInt();
int n = input;
int a = 0;
int r = 0;
for (; n > 0;){
n = n/10;
a = a + 1;
}
for (int y = 0; y < input;a--) {
r =(int)( r + input%10*pow(10,a-1));
input = input/10;
}
System.out.println(r);
}
}