I am currently working on a simple program where you're asked "How many random numbers between 0 - 999 do you want?" You enter a value (lets say 3), and it prints "Here are your numbers:" "213 52 821".
How do I go about making the random numbers print in ascending order, from smallest to biggest. I don't want you to write the code for me, just some pointers.
I am really new to programming
import java.util.Scanner;
import java.util.Random;
public class Main {
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.print("How many random numbers between 0 - 999 do you want? ");
int value = scan.nextInt();
System.out.println("Here are your numbers:");
int randomArray[]=new int[value];
for(int i = 0; i<value; i++)
{
randomArray [i] = (int) (Math.random () * 999);
System.out.println(randomArray[i]);
}
}
}
Seems like you have done most of the work. You just need to sort the resulting array.
Use Arrays.sort(randomArray) to sort the array.
Edit: You can print the array outside for-loop with System.out.println(Arrays.toString(randomArray));
Edit 2: In response to your comment, replace the for-loop with this code:
for(int i = 0; i<value; i++)
{
randomArray [i] = (int) (Math.random () * 999);
}
Arrays.sort(randomArray);
System.out.println(Arrays.toString(randomArray));
Edit 3: Replace the for loop in you code with this code if you want both ascending and descending order.
int[] ascendingArray = randomArray.clone();
Arrays.sort(ascendingArray);
int[] descendingArray= ascendingArray.clone();
Collections.reverse(Arrays.asList(descendingArray));
// These two lines print the random array in ascending order.
System.out.println("Sorted array (ascending order):");
System.out.println(Arrays.toString(ascendingArray));
// These two lines print the random array in descending order.
System.out.println("Sorted array (descending order):");
System.out.println(Arrays.toString(descendingArray));
import java.util.Scanner;
import java.util.*;
public class Main {
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.print("How many random numbers between 0 - 999 do you want? ");
int value = scan.nextInt();
System.out.println("Here are your numbers:");
int randomArray[]=new int[value];
for(int i = 0; i<value; i++)
{
randomArray [i] = (int) (Math.random () * 999);
//System.out.println(randomArray[i]);
}
Arrays.sort(randomArray);
System.out.println(randomArray.toString());
}
}
Related
I am stuck at this part right now with adding the groups together. So like, Array1 A + Array2 A
Array1 B + Array 2 B
This is my code:
import java.util.*;
import java.util.Arrays;
public class Math {
public static final int ARRAY1 = 5;
public static final int ARRAY2 = 5;
public static void main(String[] args) {
int de;
de = 1;
System.out.println("Welcome! This program will assist you in\n 1) Adding groups of numbers\n 2) and subtracting a group of numbers\nPlease enter the number of which you need help with!");
Scanner keyboard = new Scanner(System.in);
op = keyboard.nextInt();
if (op == 1) {
System.out.println("****Addition****\nAwesome! Please insert all the numbers for your first group of numbers!");
System.out.println("Enter "+ARRAY1+"");
int[] array = new int[ARRAY1];
for(int i=0;i<array.length;i++)
{
System.out.println("Enter value "+i);
array[i] = keyboard.nextInt();
}
System.out.println("Great! Now please enter your "+ARRAY2+" other group numbers!");
int[] array1 = new int[ARRAY2];
for(int i=0;i<array.length;i++) {
System.out.println("Enter value "+i);
array1[i] = keyboard.nextInt();
}
}
}
}
Initialize the array of the same size and then loop over adding the elements one by one from the 2 input arrays.
int[] sum_array = new int[ARRAY1]; // initialize the output array
for(int i=0;i<array.length;i++) {
sum_array[i] = array[i] + array1[i]; // adding the elements from two arrays
}
for(int i=0;i<array.length;i++) {
System.out.print(sum_array[i] + " ");
}
System.out.println();
The easiest way to solve this is to create another array, let's call it array3, with the same length as your 2 arrays. Then loop over the array3 and store the sum of array1[index] and array2[index] in the array3[index]
package selectionsortintro;
public class SelectionSortIntro {
public static void main(String[] args) {
int nums[] = { 22, 30, 15, 1, 7, 87, 65, 24, 22, 0 };
// print out unsorted list
for (int count = 0; count < nums.length; count++) {
System.out.print(nums[count] + " ");
}
System.out.println("\n---------------------------------");
selectionSort(nums);
// print out sorted list
System.out.println("After sorting using the Selection Sort," + " the array is:");
for (int count = 0; count < nums.length; count++) {
System.out.print(nums[count] + " ");
}
}
public static void selectionSort(int data[]) {
int smallest;
for (int i = 0; i < data.length - 1; i++) {
smallest = i;
// see if there is a smaller number further in the array
for (int index = i + 1; index < data.length; index++) {
if (data[index] < data[smallest]) {
swap(data, smallest, index);
}
}
}
}
public static void swap(int array2[], int first, int second) {
int hold = array2[first];
array2[first] = array2[second];
array2[second] = hold;
}
}
I want to add a random amount of random integers into the array, so the selection sort algorithm will sort them out. The only problem is, I don't know how to store the array with random numbers and not be a fixed amount. If that's confusing, when you make the array it's like :
int[] randomNumbers = new int[20];
Where 20 is the amount of numbers generated. Well I want to have the user be the judge of how many numbers are randomly generated into the array. So I'm thinking maybe use ArrayList? But then, I get confused as to how I can use it to add the random numbers into itself. If anyone can help me that'd be awesome
EDIT: So I got input using scanner, but I really would prefer JOptionPane as the input dialog looks a lot nicer, but if scanner is the only way that's fine. So now that that's done, I just need to actually FILL the array with random integers, does anyone know how to do that?
Here's what I came up with, I get an error with my code, if anyone could help that'd be awesome.
Scanner input = new Scanner(System.in);
Scanner s = new Scanner(System.in);
System.out.println("enter number of elements");
int n = s.nextInt();
int nums[]=new int[n];
Random randomGenerator = new Random();
//print out unsorted list
for (int count = 0; count < nums.length; count++) {
System.out.print(nums[count] + " ");
nums[n] = randomGenerator.nextInt(1001);
}
Here's an example using a traditional array and a JOptionPane:
import javax.swing.*;
import java.util.Random;
public class Random_int_array {
public static void main(String[] args) {
JFrame frame = new JFrame("Total number of integers");
int iTotalCount = Integer.parseInt(JOptionPane.showInputDialog(frame, "What is the total number of integers?"));
int[] array = new int[iTotalCount];
Random randomGenerator = new Random();
for(int i=0; i < iTotalCount; i++){
array[i] = randomGenerator.nextInt(1001);
}
// Now you can do whatever processing you would like to do
// For the sake of this answer, I will just print the numbers
for(int i=0; i < array.length; i++){
System.out.println(array[i]);
}
// We should explicitly call exit because we used a form/window
System.exit(0);
}
}
And here's an example of using an ArrayList with JOptionPane instead of a regular int[] array;
import javax.swing.*;
import java.util.Random;
import java.util.ArrayList;
public class Random_int_array {
public static void main(String[] args) {
JFrame frame = new JFrame("Total number of integers");
int iTotalCount = Integer.parseInt(JOptionPane.showInputDialog(frame, "What is the total number of integers?"));
// Can also be written as: ArrayList<Integer> array = new ArrayList<>();
// in newer versions of Java.
ArrayList<Integer> array = new ArrayList<Integer>();
Random randomGenerator = new Random();
for(int i=0; i < iTotalCount; i++){
array.add(randomGenerator.nextInt(1001));
}
// Now you can do whatever processing you would like to do
// For the sake of this answer, I will just print the numbers
for(int i=0; i < array.size(); i++){
System.out.println(array.get(i));
}
// We should explicitly call exit because we used a form/window
System.exit(0);
}
}
Note: ArrayLists cannot use primitive data types, so you must specify it as using an Integer rather than an int.
Adding an option to set the size of the array based off of user input is a bit more tricky
The easiest way to code it is to pass in command line arguments and read them in your args variable in your main method
Another way to read input is the Scanner class
Whichever way you choose, you may end up with a String variable you need to convert to an int with
String input = args[0]; //or use Scanner
int size = Integer.parseInt(input);
Three different methods of generating random integers, from easiest to implement to hardest
To generate a random int [0, max)
(int)(Math.random() * max)
or use
Random r = new Random();
r.nextInt(max);
A more complicated way to generate a more random number instead of Java's pseudo-random generators would be to query random.org for data. Do note that this may take a bit longer to set up and code, as well as relying on third party servers (no matter how reliable they may be)
You can use the random int to initialize the input array with a random length, then fill in the values with random numbers with a for loop
I have an array a[5][5] and several values. I want to randomly assign values based on random percentages I create. For example one value is 6 and 25% of the elements in the array should have the value 6. With what I have so far: I created the random percentages and I'm able to randomly assign values for different elements in the array. My problem is: more than 25% of the elements have 6. My question is: How do I make sure that when assigning elements with 6, exactly 25% of the elements in the array a[5][5] have that value? I'm new to programming and tried several loops and ifs but nothing is working out for me. Please push me towards the right direction.
25% of 25 is about 6. It is not accurate. Here is a possible solution.
import java.util.Random;
import java.util.Scanner;
public class Matrix25 {
public static void main(String[] args) {
int[][] Matrix = new int[5][5];
Scanner scanner = new Scanner(System.in);
System.out.print("Enter the number you want to fill the array to 25%: ");
int number = scanner.nextInt();
int percentage=25;
generateMatrix(Matrix,number,percentage);
printMatrix(Matrix);
}
public static void generateMatrix(int Matrix[][],int num, int perc) {
int n;
int max=Matrix.length*Matrix[0].length;
int[] numbers = new int[max];
Random rnd = new Random();
int m = (int)(max * (perc/100.0));
int x=num>m?m-1:m;
for(int i=0;i<max;i++)
numbers[i]=(i<x)?num:i+1;
for(int i=0;i<Matrix.length;i++)
for(int j=0;j<Matrix[i].length;j++) {
n=rnd.nextInt(max);
Matrix[i][j]=numbers[n];
numbers[n]=numbers[max-1];
max--;
}
}
public static void printMatrix(int Matrix[][]) {
for(int i=0;i<Matrix.length;i++) {
for(int j=0;j<Matrix[i].length;j++)
System.out.printf("%3d\t",Matrix[i][j]);
System.out.print("\n");
}
}
}
I would do it like this
import java.util.Random;
import java.util.Scanner;
class Random2darray {
/**
* #param args
*/
public static void main(String[] args) {
// Create array; you specified 5x5 but you probably shouldn't hard code like this
int[][] numbers = new int[5][5];
//Create a scanner to get user input
Scanner scanner = new Scanner(System.in);
//I am not doing anything to make sure they give a decimal so the program won't work
//right if you are not giving a decimal
System.out.println("How much do you want to fill? Enter a decimal.");
//Get a double
double populatePercentage = scanner.nextDouble();
System.out.println("What number do you want to fill with?");
//Get an int
int fillNumber = scanner.nextInt();
//Don't hardcode like this
int fillTimes = numberOfTimesToFill(25, populatePercentage);
//This is declared outside of the loops because otherwise it will be
//reset each time the loop runs
int count = 0;
//Create a random number generator; default seed is current time which is good enough for this
Random rand = new Random();
//Fill the array with numbers
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
//Check if you have filled with given number enough times
if(count < fillTimes){
numbers[i][j] = fillNumber;
//Increment count by 1; this is how you are keeping track
count++;
}else{
//Otherwise pick a random number generator
//This will pick a random int between 0 - 50 inclusive
int randomNumber = rand.nextInt(51);
//This will make sure that you are not generating random numbers that are the same
//as the number you are filling with; This says if it is the same generate a new number
while(randomNumber == fillNumber){
randomNumber = rand.nextInt(51);
}
//Once we know its random fill the spot in the array
numbers[i][j] = randomNumber;
}
}
}
//Print the array out
printArray(numbers);
}
private static void printArray(int[][] numbers) {
//Just loop through and print every number
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
//Print with formatting: this says print a digit (%d) followed by a
//tab(\t) and then specifies what number I want to print
System.out.printf("%d\t", numbers[i][j]);
}
//Print a new line after each row
System.out.printf("\n");
}
}
private static int numberOfTimesToFill(int elements, double populatePercentage) {
System.out.println((int)(populatePercentage * elements));
//Cast to an int to truncate the decimal part of the number because you can't have
//a fraction of an element
return (int)(populatePercentage * elements);
}
}
I have commented the code to explain what everything does. However it does not protect against bad user input and it hardcodes the size of the array, you should always try to avoid hardcoding. In this example I did it (and marked where) to be more clear. Also as was mentioned in the comments above, for your situation where you want exactly 25% of 25 is not possible. This is because .25 * 25 = 6.25 and you can't have .25 of an element.
I'm trying to create a code that lets the user determine the size and elements of an array and then print it out. So far I have this.
import java.util.Scanner;
public class test3 {
public static void main (String[] args)
{
Scanner keyboard=new Scanner(System.in);
System.out.println("Input how many numbers you want to find the median for (numerical value) :");
int num = keyboard.nextInt();
System.out.println("Please enter " + num + " numbers.");
int[] values = new int[num];
for (int i = 0; i < num; i++) {
values[i] = keyboard.nextInt();
System.out.println(values[i]);
}
}
}
I don't know if it is right because when a user inputs the size and then the elements, the code is just displaying the element as the user inputs it. For example,
input how many numbers you want to find the median for
5
please enter 5 numbers
3//user input
3//what is displayed.
I want to make it so that the user inputs all of their numbers and THEN it displays the inputed numbers as an array.
We are not allowed to use the array class by the way.
import java.util.Scanner;
public class test3 {
public static void main (String[] args) {
Scanner keyboard=new Scanner(System.in);
System.out.println("Input how many numbers you want to find the median for (numerical value) :");
int num = keyboard.nextInt();
System.out.println("Please enter " + num + " numbers.");
int[] values = new int[num];
for (int i = 0; i < num; i++) {
values[i] = keyboard.nextInt();
}
for (int i = 0; i < num; i++) {
System.out.println(values[i]);
}
}
}
Your for loop will execute for as many number as the user has entered, in your test case 5. Every iteration will take a number from the keyboard input, place it into the array and display it. Since you want to capture all the numbers first and then want to display them you should remove
System.out.println(values[i]);
from the for loop and place that into another for loop to display the numbers like so
for(int x=0 ;i < num ; i++)
{
System.out.println(values[x]);
}
This way the first loop will gather all the numbers and after the numbers are collected the second loop will display the numbers one by one iterating over the array.
Hope this helps!
Im working on an assignment for a beginners Java course, and Im having a problem with printing out an array the way that its asking for. The problem is as follows:
"Write a program that asks the user "How many numbers do you want to enter?" With that value, create an array that is big enough to hold that amount of numbers (integers). Now ask the user to enter each number and store these numbers into the array. When all the numbers have been entered, display the numbers in reverse order from the order in which they were entered."
I have everything except the last part, displaying the numbers in reverse order.
Any help on this would be appreciated.
Heres What I have so far:
import java.util.Scanner;
public class ArraysNickGoldberg
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("How many numbers do you want to enter?");
final int NUMBER_OF_ELEMENTS = input.nextInt();
int[] myList = new int[NUMBER_OF_ELEMENTS];
for( int i = 0; i < NUMBER_OF_ELEMENTS; i++) {
System.out.println("Enter a new number: ");
myList[i] = input.nextInt();
}
for( int i = 0; i < NUMBER_OF_ELEMENTS; i++){
System.out.print(myList[i] + " ");
}
}
}
try
for( int i = NUMBER_OF_ELEMENTS - 1; i >= 0; i--){
System.out.print(myList[i] + " ");
}
You may also want to look at
Java Array Sort
to print it in reverse order, you just need to simply reverse your for loop :)
so instead of
for(int i=0; i< NUMBER_OF_ELEMENTS; i++){
}
use this instead:
for(int i=NUMBER_OF_ELEMENTS - 1; i >= 0; i--){ //remember to minus 1 or else you'll get index of out of bound
}