I am stuck in my beginner java course and am trying to get my array to print out with the user's input on randomly selected index's. With the code I have so far it will only print out an index with all 0's such as this "{0, 0, 0, 0, 0, 0}"
Here is the prompt:
Create an empty int array of size 6.
Create a method called populateArray that will pass an array, use random class to choose a random index and prompt the user to enter a value, store the value in the array. Note: Generate 6 random index numbers in an attempt to fill the array.
Create a method called printArray that prints the contents of the array using the for each enhanced loop.
Here is my code:
public class ChangeUp {
public static void main(String[] args) {
int[] array = new int[6];
System.out.println("Please enter 6 numbers to add to a list.");
populateArray(array);
printArray(array);
}
public static void populateArray(int[] array) {
Random r = new Random();
Scanner input = new Scanner(System.in);
int rArray = r.nextInt(array.length);
int i = 0;
for (i = rArray; i <= array.length; i++) {
i = input.nextInt();
}
}
public static void printArray(int[] array) {
System.out.print("{" + array[0]);
for (int i = 1; i < array.length; i++) {
System.out.print(", " + array[i]);
}
System.out.println("}");
}
}
for (int i = rArray; i <= array.length; i++) {
i = input.nextInt();
}
Here is your problem. You assign the value(s) to i, not to elements of the array.
Turn:
i = input.nextInt();
into:
array[i] = input.nextInt();
You do not change any values of array. You can do it with array[i] = value where i is index which value you want to change.
Here is example of what populateArray would looks like:
public static void populateArray(int[] array) {
Random r = new Random();
Scanner input = new Scanner(System.in);
int i = r.nextInt(array.length);
array[i] = input.nextInt();
}
You did not assigne input values to the array: array[i] = ....
I would recommend you to not randomly insert an elements, but just fill an array and then shuffle it.
public class ChangeUp {
public static void main(String... args) {
int[] arr = new int[6];
System.out.format("Please enter %d numbers to add to a list:\n", arr.length);
populateArray(arr);
printArray(arr);
}
public static void populateArray(int... arr) {
Scanner scan = new Scanner(System.in);
List<Integer> tmp = new ArrayList<>(arr.length);
for (int i = 0; i < arr.length; i++)
tmp.add(scan.nextInt());
Collections.shuffle(tmp);
int i = 0;
for (int val : tmp)
arr[i++] = val;
}
public static void printArray(int... arr) {
System.out.println(Arrays.stream(arr)
.mapToObj(String::valueOf)
.collect(Collectors.joining(", ", "{", "}")));
}
}
Demo:
Please enter 6 numbers to add to a list:
1
2
3
4
5
6
{4, 3, 1, 5, 2, 6}
Related
public class ForEach {
Scanner sc = new Scanner(System.in);
int[] arr = new int[5];
void setMarks()
{
for(int j : arr)
{
arr[j] = sc.nextInt();
}
}
void getMarks()
{
for(int k : arr)
{
System.out.println(arr[k]);
}
}
public static void main(String[] args)
{
System.out.println("Enter the marks of 5 subjects : ");
ForEach fe = new ForEach();
fe.setMarks();
System.out.println(fe.arr.length);
fe.getMarks();
}
}
I am just trying to input marks of 5 subjects and display it on the screen. I got this error
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds for length 5
at ForEach.getMarks(ForEach.java:17)
at ForEach.main(ForEach.java:27)
Your getMarks function is reading an integer out of the array and then trying to go to the position in the array indicated by that integer. If your array has one element and is { 100 }, the code inside your loop will try to print the 100th (really 101st because the index starts at 0) element in your array.
The following code should fix the issue:
void getMarks()
{
for(int k : arr) {
System.out.println(k);
}
}
Also, your setMarks method would set data to only the 0th index. Because "j" points to the value and not to the index.
you might have to refactor you setMarks method like the below -
int pos = 0;
for(int j:arr){
arr[pos] = sc.nextInt();
pos++;
}
or better use the normal for loop.
You use for loop incorrectly. It has two ways to use.
First way
int[] arr = new arr[10];
for(int i = 0; i < arr.length; i++)
arr[i] = 1;
This will set 1 to all elements.
Just why 99% of all usage of for loop just iterates over an array, there is the second way.
int[] arr = { 1,2,3 };
for(int a : arr)
System.out.print(a); // print 123
// i.e. the same
for(int i = 0; i < arr.length; i++)
System.out.print(arr[i]);
Note, that this way you can use only to read element from array from first to last elements.
So, you should change your code to:
public class ForEach {
Scanner sc = new Scanner(System.in);
int[] arr = new int[5];
void setMarks() {
for(int i = 0; i < arr.length; i++)
arr[i] = sc.nextInt();
}
void getMarks() {
for(int a : arr)
System.out.println(a);
}
public static void main(String[] args)
{
System.out.println("Enter the marks of 5 subjects : ");
ForEach fe = new ForEach();
fe.setMarks();
System.out.println(fe.arr.length);
fe.getMarks();
}
}
public static void find( int[] numbers) {
int[] range = new int[5];
for(int i=0; i<numbers.length; i++)
{
if(numbers[i]>=10 && numbers[i] <= 20)
{
range[i]=range[i]+numbers[i];
}
}
}
I want to write a method that find the numbers between 10 and 20 in a array and assign them to another array. this is expected and this is what I got.
{ 0 0 0 } are between 10 - 20 how can I fix this ?
public static void read( int[] numbers) {
Scanner input = new Scanner(System.in);
for( int i=0; i<numbers.length;i++)
{
System.out.print("Number["+i+"] => ");
numbers[i] = input.nextInt();
}
input.close();
}
This is the read() method that reads numbers from user and assign to an array.
public static void print( int[] numbers, int[]range) {
System.out.println("Number = { "+ numbers[0]+" "+numbers[1]+" "+numbers[2]+" "+numbers[3]+" "+numbers[4]+" }");
System.out.println("{ "+range[0]+" "+range[1]+" "+range[2]+" } "+" are between 10 - 20 ");
}
And this is the print(x,y) method that prints the numbers and range arrays.
My main method is:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[] numbers = new int[5];
read( numbers );
int[] range = new int[5];
find( numbers );
print(numbers, range);
The numbers array must include 3 numbers between 10-20.
Solution
Change the return type of your function to int[]
precalculate the size of your ranges array with counter
store the values which are in your range in the range array
return the range array
Note dont use the i running variable also for your range array, if you do so when not every value is in your range the result array will have gaps meaning values with the value of zero.
In the read function you should return the readed-in values to use it then in your find function
public static int[] read(int size) {
Scanner input = new Scanner(System.in);
int[] numbers = new int[size];
for(int i=0; i < size; i++)
{
System.out.print("Number["+(i+1)+"] => ");
numbers[i] = input.nextInt();
// to remove the new line character
input.nextLine();
}
input.close();
return numbers;
}
import java.util.*;
public class MyClass {
public static void main(String args[]) {
int[] values = MyClass.read(10);
int[] result = MyClass.find(values);
// result is now the return value of the find method
// you can parse it now to another method of your choice
System.out.println(Arrays.toString(result));
}
public static int[] find(int[] numbers) {
int counter = 0;
for (int i = 0; i < numbers.length; i++) {
if (numbers[i] >= 10 && numbers[i] <= 20) {
counter++;
}
}
int[] range = new int[counter];
int counter2 = 0;
for (int i = 0; i < numbers.length; i++) {
if (numbers[i] >= 10 && numbers[i] <= 20) {
range[counter2] = numbers[i];
counter2++;
}
}
return range;
}
public static int[] read(int size) {
Scanner input = new Scanner(System.in);
int[] numbers = new int[size];
for (int i = 0; i < size; i++) {
System.out.print("Number[" + (i+1) + "] => ");
numbers[i] = input.nextInt();
// to remove the new line character
input.nextLine();
}
input.close();
return numbers;
}
}
1. You need to return the 'range' array in the 'find' function because otherwise, it isn't accessible.
2. You need another variable say 'j' to point to the indices of the 'range' array.
The same variable can't be used for both the 'numbers' array and the 'range' array.
3. It will be better to pass the size of the 'numbers' array through the 'read' function and then read the array using the 'read' function.
Functions:
find() function:
public static int[] find( int[] numbers) {
int[] range = new int[5];
int j = 0;
for(int i=0; i<numbers.length; i++)
{
if(numbers[i]>=10 && numbers[i] <= 20)
{
range[j]=range[j]+numbers[i];
j++;
}
}
return range;
}
read() function:
public static int[] read( int n) {
int[] numbers = new int[n];
Scanner input = new Scanner(System.in);
for( int i=0; i<numbers.length;i++)
{
System.out.print("Number["+i+"] => ");
numbers[i] = input.nextInt();
}
input.close();
return numbers;
}
print() function[Remains same]:
public static void print( int[] numbers, int[]range) {
System.out.println("Number = { "+ numbers[0]+" "+numbers[1]+" "+numbers[2]+" "+numbers[3]+" "+numbers[4]+" }");
System.out.println("{ "+range[0]+" "+range[1]+" "+range[2]+" } "+" are between 10 - 20 ");
}
Main function accordingly:
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int n = s.nextInt();
int[] numbers = read(n);
int[] range = find(numbers);
change(numbers);
print(numbers, range);
}
I created my arrays and when I am entering the values for the arrays, they are being shown on separate lines for example...
Enter the values for the first array: 75
48
23
I would like the numbers to be shown on the same line and not sure how to do it. Thank you for your help.
public class CompareArrays
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int arraySize;
System.out.print("Enter the array size: ");
arraySize = input.nextInt();
int[] array1 = new int[arraySize];
int[] array2 = new int[arraySize];
System.out.print("Enter the values for the first array: ");
for(int i = 0; i < arraySize; i++) {
array1[i] = input.nextInt();
}
System.out.print("Enter the values for the second array: ");
for(int i = 0; i < arraySize; i++) {
array2[i] = input.nextInt();
}
if(Compare(array1, array2)) {
System.out.println("Judgement: \t The arrays are identical");
}else {
System.out.println("Judgement: \t The arrays are not identical");
}
input.close();
}
public static boolean Compare(int[] array1, int[] array2)
{
for (int i = 0; i < array1.length; i++) {
if(array1[i] != array2[i]) {
return false;
}
}
return true;
}
}
When in the console inputting those values you are hitting enter which is why it looks like it is on different lines. If you want to input the values on 1 line you could possibly input them as a string and split it.
If you're looking to just print the array on one line you can do that with a basic for loop and using System.out.print().
int[] a = {1, 2, 3, 4};
for(int i = 0; i < a.length; i++) {
System.out.print(a[i] + " ");
}
I am new to java programming and i am trying to sort arrays using Arrays.sort() function. After using Arrays.sort(array),I am printing the final sorted array.
For example:
Input : 1 3 2 4
Output comes as : 0 0 0 0.
import java.io.*;
import java.util.Scanner;
import java.util.Arrays;
public class TestClass {
public static final int MAX_SIZE = 20;
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int n,temp,count;
int[] array = new int[MAX_SIZE];
n = input.nextInt();
for(int i = 0 ; i < n ; ++i) {
array[i] = input.nextInt();
}
Arrays.sort(array);
for(int i = 0 ; i < n ; ++i) {
System.out.print(array[i]+" ");
}
}
}
You have initialized you array to hold 20 integers but you input only 5. Hence the first 15 elements will be 0 followed by the numbers you have inputted once the array is sorted.
To fix the issue you can initialize the array with n instead of MAX_SIZE as shown below:-
n = input.nextInt();
int[] array = new int[n];
Set the size of the array to match what your input should be, not to the maximum allowed size:
public class TestClass {
public static final int MAX_SIZE = 20;
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int n, temp, count;
n = input.nextInt();
if (n > MAX_SIZE) {
//handle error somehow
}
int[] array = new int[n];
for (int i = 0; i < n; ++i) {
array[i] = input.nextInt();
}
Arrays.sort(array);
for (int i = 0; i < n; ++i) {
System.out.print(array[i] + " ");
}
}
}
When you initialize an array in Java it gets default value of 0 for primitive int:
int[] array = new int[MAX_SIZE];
The fact that you are not seeing your desired input of 1,2,3,4 is a separate problem with your Scanner code.
Have a program where the user inputs 10 int values into the array. Lastly I need to pull out the distinct values and display them. Added my second for loop which would determine if the the value is distinct (i.e. meaning if the number appears multiple times it is only displayed once).
For instance, let say I pass in the numbers: 1, 2, 3, 2, 1, 6, 3, 4, 5, 2 the distinct array should only contain numbers {1, 2, 3, 6, 4, 5}
import java.util.Scanner;
import java.io.*;
public class ArrayDistinct {
public static void main(String[] args) throws IOException {
Scanner input = new Scanner(System.in);
// Create arrays & variables
int arrayLength = 10;
int[] numbers = new int[arrayLength];
int[] distinctArray = new int[arrayLength];
int count = 0;
System.out.println("Program starting...");
System.out.print("Please enter in " + numbers.length + " numbers: ");
for (int i = 0; i < numbers.length; i++) {
numbers[i] = input.nextInt();
}
for (int i = 0; i < numbers.length; i++) {
int temp = numbers[i];
int tempTwo = numbers[i + 1];
if (tempTwo == temp) {
count++;
distinctArray[i] = temp;
}
}
// Print out results
} // end main
} // end class
Try this :
Set<Integer> uniqueNumbers = new HashSet<Integer>(Arrays.asList(numbers));
uniqueNumbers will contain only unique values
In Java 8
Stream< T > distinct()
Returns a stream consisting of the distinct elements (according to
Object.equals(Object)) of this stream. For ordered streams, the
selection of distinct elements is stable (for duplicated elements, the
element appearing first in the encounter order is preserved.) For
unordered streams, no stability guarantees are made.
Code:
Integer[] array = new Integer[]{5, 10, 20, 58, 10};
Stream.of(array)
.distinct()
.forEach(i -> System.out.print(" " + i));
Output:
5,10,20,58
Read More About distinct function
Try this code.. it will work
package Exercises;
import java.util.Scanner;
public class E5Second
{
public static void main(String[] args)
{
Scanner In = new Scanner(System.in);
int [] number = new int [10];
fillArr(number);
boolean [] distinct = new boolean [10];
int count = 0;
for (int i = 0; i < number.length; i++)
{
if (isThere(number,i) == false)
{
distinct[i] = true;
count++;
}
}
System.out.println("\nThe number of distinct numbers is " + count);
System.out.print("The distinct numbers are: ");
displayDistinct(number, distinct);
}
public static void fillArr(int [] number)
{
Scanner In = new Scanner(System.in);
System.out.print("Enter ten integers ");
for (int i = 0; i < number.length; i++)
number[i] = In.nextInt();
}
public static boolean isThere(int [] number, int i)
{
for (int j = 0; j < i; j++)
if(number[i] == number[j])
return true;
return false;
}
public static void displayDistinct(int [] number, boolean [] distinct)
{
for (int i = 0; i < distinct.length; i++)
if (distinct[i])
System.out.print(number[i] + " ");
}
}
One possible logic: If you're supposed to only sort out "unique" numbers, then you'll want to test each number as it's entered and added to the first array, and loop through the array and see if it's equal to any of the numbers already there; if not, add it to the "unique" array.
Sets in java doesn't allow duplicates:
Integer[] array = new Integer[]{5, 10, 20, 58, 10};
HashSet<Integer> uniques = new HashSet<>(Arrays.asList(array));
That's it.
Something like this should work for you:
Scanner input = new Scanner(System.in);
// Create arrays & variables
int arrayLength = 10;
int[] numbers = new int[arrayLength];
int[] distinctArray = new int[arrayLength];
int count = 0;
Set<Integer> set = new HashSet<Integer>();
System.out.println("Program starting...");
System.out.print("Please enter in " + numbers.length + " numbers: ");
for (int i = 0; i < numbers.length; i++) {
set.add(input.nextInt());
}
for(Integer i : set)
{
System.out.println("" + i);
}
This will only add unique values to the set.
int a[] = { 2, 4, 5, 3, 3, 3, 4, 6 };
int flag = 0;
for (int i = 0; i < a.length; i++)
{
flag = 0;
for (int j = i + 1; j < a.length; j++)
{
if (a[i] == a[j])
{
flag = 1;
}
}
if (flag == 0)
{
System.out.println(a[i]);
}
}