I am just starting out in Java and I have searched through the internet for several hours and cannot seem to find something to help me on an assignment. I have an array and I need to write a method for it. It seems easy but I cannot seem to connect the two together. I understand the methods but we did not go over using them with arrays so I am totally confused. If there is a similar answer on here, please point me in the right direction.
Thank you for your time.
Question:
Write a method which takes in an integer from the user between 1 and 10 and determines if that number is part of the randomly generated array. It must have a method signature of (int []) and return a boolean.
public class ArrayExample {
public int [] createRandomArray() {
int size = (int) (Math.random() * 10) + 1;
int[] array = new int [size];
for (int i = 0; i < array.length; i++) {
array[i] = (int) (Math.random() * 10 ) + 1;
}
return array;
}
public static void main(String [] args) {
}
}
It will be something like below:
public class ArrayExample {
public static int [] createRandomArray() {
int size = (int) (Math.random() * 10) + 1;
int[] array = new int [size];
for (int i = 0; i < array.length; i++) {
array[i] = (int) (Math.random() * 10 ) + 1;
}
return array;
}
private static boolean checkForNumInArray(int[] randomArrayInput){
//your logic goes here
// ask user for input number - Scanner/BufferedReader
//search for that number in array - Loops
// if found return true, otherwise return false - if-else
}
public static void main(String [] args) {
int[] randomArray = createRandomArray();
boolean isPresent = checkForNumInArray(randomArray);
}
}
You can go through the code to have understanding
public class ArrayExample {
public int [] createRandomArray() {
int size = (int) (Math.random() * 10) + 1;
int[] array = new int [size];
for (int i = 0; i < array.length; i++) {
array[i] = (int) (Math.random() * 10 ) + 1;
}
return array;
}
public int getUserInput() {
//Take input from user and check it is between 1 and 10.
}
public boolean search(int[] arr, int input) {
// Use some searching algorithm. Linear search will suit as the array is randomly generated.
// if input is present in array return true else return false.
}
public static void main(String [] args) {
int input = getUserInput();
boolean result = search(createRandomArray(), input);
//Print a message based on result.
}
}
In the main method you simply have to iterate the loop of integers from one to ten and check if it is present in the array you have created.
public static void main(String[] args) {
int arr[] = createRandomArray();
for(int i=0;i<=10;i++) {
if(Arrays.binarySearch(arr, i) == 0) { System.out.println("yes"); }
}
}
Related
I am new to coding and trying to call a method (RandomArray) which I wrote and defined in a separate class, but in my driver code I am getting following error message:
Couldn't find symbol- RandomArray().
the code SHOULD create an array (size of which is chosen by the user) and then populate it with random numbers and output the Highest, Lowest, and Average of the numbers in said array.
All spellings match up, and the call itself works and displays no errors, but when using it in the for-loop I get the error message.
This is the class where I created the method:
import java.util.Random;
public class RandomArray
{
//things declared at class level
public int minimun,maximun,adverage, mn, mx, avg;
public String range;
//constucotr for inital numbers
public RandomArray()
{
minimun = 0;
maximun = 1000 + 1;
}
static int RandomArray()
{
Random ran = new Random();
return (ran.nextInt(1000) + 1);
}
//define types
public RandomArray (int mn, int mx, String r, int a)
{
minimun = mn;
maximun = mx;
range = r;
adverage = a;
}
//set minimun
public void setMinimun (int m)
{
minimun = mn;
}
//get minimun
public int getMinimun()
{
return minimun;
}
//set maximun
public void setMaximun(int x)
{
maximun = mx;
}
//get maximun
public int getMaximun()
{
return maximun;
}
//compute adverage
public int adverage(int...array)
{
int adverage = 0;
if (array.length > 0)
{
int sum = 0;
for(int num : array)
sum = sum + num; //add numbers in array
adverage = (int)sum / array.length; //divide numbers in array by the array lenth
}
return adverage;
}
//return values as a string
public String toString()
{
return String.valueOf(getMinimun() + getMaximun() + adverage());
}
}
And this is the driver program that should be populating the array (of users choice) with random numbers and printing the highest, lowest and average:
import java.util.Random;
import java.util.Scanner;
import java.util.Arrays;
public class DemoRandomArray
{
// variable go here
final int minimun = 0;
public static void main(String[] args)
{
final int max = 100;
RandomArray ra = new RandomArray();
int[] anArray = new int[1000];
for(int i=1; i < max; i++)
{
System.out.println(RandomArray());
}
}
}
The method is inside another class, so you need to use the class name.
RandomArray.RandomArray() instead of just RandomArray()
How to use multiple methods in a code? First it asks for the size of an array, then for the numbers of the element. One method is rounding numbers with a special rule.
Second method is a void method which modifies the array. Third method is making a new array with the modified values and returns to this array.
package tombtombbekerekit;
import java.util.Scanner;
public class TombTombbeKerekit {
public static int round(int osszeg)
{
int last_Digit = osszeg % 10;
if(last_Digit < 3)
return osszeg - last_Digit;
else if(last_Digit > 7)
return osszeg + (10 - last_Digit);
else
return osszeg - (last_Digit) + 5;
}
public static void roundSelf(int [] numbers)
{
int[] array = numbers;
for (int i = 0; i < array.length; i++)
return;
}
public static int [] roundNew(int [] numbers)
{
int [] newArray = new int[numbers.length];
return newArray;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Kérem az összegek számát: ");
int size = sc.nextInt();
System.out.println("Kérem az összegeket: ");
int [] array = new int[size];
for (int i = 0; i < array.length; i ++)
{
array[i] = sc.nextInt();
}
int [] kerek = roundNew(array);
System.out.println("Kerekítve: ");
for (int i = 0; i < kerek.length; i++)
System.out.println(kerek[i]);
}
}
You should write your own function. Just find the rule for the rounding. You can use n%10 to get the last digit of an integer named n.
I've written something but haven't tested it, I believe it should work. Check it out:
public int weirdRounding(int n)
{
int last_Digit = n % 10;
if(last_Digit < 3)
return n - last_Digit;
else if(last_Digit > 7)
return n + (10 - last_Digit);
else // the last digit is 3,4,5,6,7
return n - (last_Digit) + 5;
}
Note: You should probably make this code more readable if you're going to use it. For example define int LOWER_BOUND = 3 and int UPPER_BOUND = 7 instead of using '3' and '7', you could also wrap the ugly expressions with functions (e.g. roundUp, roundToFive ..). #Magic_Numbers_Are_Bad
I am having problems understanding a program I need to write for class. My program works as it should, but the problem states that it wants me to not print within my methods. I am confused on how I should output my values because my methods must be void according to the problem (which doesn't return anything) and I can't print inside of them.
Here is the question:
Design and implement a java program (name it ArrayMethods), that defines 4 methods as follows:
int arrayMax (int[] array)
int arrayMin (int[] array)
void arraySquared (int[] array)
void arrayReverse (int[] array)
Test your methods by creating an array of length 5 within your main method and filling it with random numbers between 1 and 1000. Your program should then display the original array, display the smallest number in the array, display the greatest number in the array, display the revered array, and display the square of each value in the array. You main method shoudl invoke each method exactly once, with each invocation use the original array as the actual parameter. No printing within the methods. Document your code, and organize/space your outputs properly. Use escape characters and formatting objects when applicable.
So again my question is: How do I use those methods without printing anything if I can't return a value? If anyone could give me a clue on how to solve this, it would be greatly appreciated.
import java.util.Random;
import java.util.Arrays;
public class ArrayMethods
{
public static void main (String[] args)
{
int[] array = new int[5];
array[0] = (int)(Math.random() * (1000 - 1)) + 1;
array[1] = (int)(Math.random() * (1000 - 1)) + 1;
array[2] = (int)(Math.random() * (1000 - 1)) + 1;
array[3] = (int)(Math.random() * (1000 - 1)) + 1;
array[4] = (int)(Math.random() * (1000 - 1)) + 1;
System.out.println("The values within the array are: " + Arrays.toString(array));
System.out.println("The maximum value within the array is: " + arrayMax(array));
System.out.println("The minimum value of the array is: " + arrayMin(array));
System.out.print("The values within the array (squared) are: ");
arraySquared(array);
System.out.print("\n");
System.out.print("The array reversed is: ");
arrayReverse(array);
}
public static int arrayMax (int[] array)
{
int max = 0;
for (int i = 0; i < array.length; i++)
{
if (array[i] > max)
{
max = array[i];
}
}
return max;
}
public static int arrayMin (int[] array)
{
int min = 1000;
for (int i = 0; i < array.length; i++)
{
if (array[i] < min)
{
min = array[i];
}
}
return min;
}
public static void arraySquared (int[] array)
{
int[] array2 = new int[5];
for (int i = 0; i < array.length; i++)
{
array2[i] = array[i] * array[i];
System.out.print(array2[i]);
while ( i < array.length - 1)
{
System.out.print(", ");
break;
}
}
}
public static void arrayReverse (int[] array)
{
for(int i = array.length - 1; i >= 0; i--)
{
System.out.print(array[i] + " ");
}
}
}
For the void functions, in C# you'd simply use an "out" or "ref" keyword. If they insist on Java, Java doesn't have an equivalent, but you can do something like that with an object.
public class PassArray
{
public int[] array;
public PassArray(int[] array)
{
this.array = array;
}
}
public static void Reverse(PassArray arrayHolder)
{
int[] reversed = new int[arrayHolder.array.Length];
int j = 0;
for (int i = arrayHolder.array.Length - 1; i >= 0; i--)
{
reversed[j] = arrayHolder.array[i];
j++;
}
arrayHolder.array = reversed;
}
static void Main(string[] args)
{
int[] toReverse = new[] { 10, 30, 2, 1, 3, 100, 340 };
PassArray passedObject = new PassArray(toReverse);
Reverse(passedObject);
// passedObject.array will now have the reversed array
}
Obviously this could can be improved but it should at least give the right idea.
My question is a very basic one. To give a bit of background, I was given an assignment to write a program that stored 100 unique (i.e no repeats)values into an array and displayed them. I thought I was on the right track earlier, but when I did a test run, all I keep getting is an "out of bounds error." Eclipse tells me it's in the method "checkDouble" but I can't seem to find what's wrong. Can anyone here help me out?
public class exercise2 {
/*#author Paolo
* #param hundredVal array to store values
* #param input random number generator from 1-100
*/
public static int[] hundredVal = new int[100];
public static int n = (int) (Math.random()*100+1);
public static void main(String[] args) {
storeVal();
}
/*
* This method is meant to take 100 random values
* from 1-100 and store them into the array hundredVal
*/
private static void storeVal() {
for (int i = 0; i < hundredVal.length; i++){
hundredVal[i] = (int) (Math.random()*100+1);
if(!checkDouble(hundredVal)){
printVal();
}
}
}
//This method is meant to test if there are any repeated values
public static boolean checkDouble (int[] hundredVal){
for (int i = 0; i < hundredVal.length; i++){
for (int j = 0; i < hundredVal.length; j++){
if (hundredVal[i] == hundredVal [j] && i != j){
return true;
}
}
}
return false;
}
//this just prints out the numbers on the console.
private static void printVal(){
for (int i =0; i < hundredVal.length; i++){
System.out.println(hundredVal[i]);
}
}
}
I don't want anyone to solve the whole assignment for me. I just want to know what is causing the out of bounds error to occur.
class exercise2{
public static int[] hundredVal = new int[100];
public static int n = (int) (Math.random()*100+1);
public static void main(String[] args) {
storeVal();
printVal();
}
private static void storeVal() {
for (int i = 0; i < hundredVal.length; i++){
hundredVal[i] = (int) (Math.random()*100+1);
}
if(!checkDouble(hundredVal)){
printVal();
}
}
public static boolean checkDouble (int[] hundredVal){
for (int i = 0; i < hundredVal.length; i++){
for (int j = 0; j < hundredVal.length; j++){
if (hundredVal[i] == hundredVal [j] && i != j){
return true;
}
}
}
return false;
}
private static void printVal(){
for (int i =0; i < hundredVal.length; i++){
System.out.println(hundredVal[i]);
}
}}
You can go with appropriate java collection - in your case LinkedHashSet should do the job. It's a Set (contains unique values) and it's ordered. It's almost always better to go with collections instead of arrays.
Hi I have been having difficulty in creating a set interface that allows me to add integers to a set using an array? My biggest problem is that calling the method I don't know how to iterate through the array so that the next integer is added to the array after the previous and so forth.
public class SetInt
{
static final int LOWERRANGE = 1;
static final int UPPERRANGE = 49;
static final int NOTAMEMBER = 0;
//class constants used to represent the range of values this set can hold
//and a dummy value of 0 to represent nothing in the set
int[] anArray = new int[50];
public void add(int a)
{
anArray[1] = LOWERRANGE;
anArray[a] = a;
}
/* prints the set of numbers currently in the set
*/
public void printNumbers()
{
for(int num = 2 ; num <=47; num++)
{
if(anArray[num] != 0)
{
System.out.print(" " + anArray[num]);
}
}
}
/* return the minimum value in the set
* #return the minimum value
*/
public int min()
{
int minValue = anArray[0];
for(int i=1; i<anArray.length; i++)
{
if(anArray[i] < minValue)
{
minValue = anArray[i];
}
}
return minValue;
}