I'm trying to fill an array using a method and later print that array out.
However when I try to do so all it gives me are zeroes. I think my fill method is not working properly but I'm not sure why. I'm trying to understand arrays but so far no good. I would prefer an explanation rather than an answer. If I can get this myself it would be best.
import java.util.Scanner;
public class diverScore {
static double score = 0;
static double validDegreeOfDiff = 0;
public static void main(String[] args) {
double[] score = new double[6];
inputAllScores(score);
printArray(score);
}
public static double[] inputAllScores(double[] x) {
Scanner s = new Scanner(System.in);
double[] array_score = new double[6];
for (int i = 0; i < 6; i++) {
System.out.println("What is the score given by the judge?");
array_score[i] = s.nextDouble();
}
return array_score;
}
public static void printArray(double[] j) {
for (int i = 0; i < 6; i++) {
System.out.println("The array is:" + j[i]);
}
}
}
In your inputAllScores, you're writing to a new local array, and returning it, but you're not using the returned array. It would be better if you wrote to the array that you passed into that method (which inside the method is called x).
try
import java.util.Scanner;
public class DiverScore {
static double score = 0;
static double validDegreeOfDiff = 0;
public static void main(String[] args) {
// double[] score = new double[6];
double[] score = inputAllScores(/*score*/);
printArray(score);
}
public static double[] inputAllScores(/*double[] x*/) {
Scanner s = new Scanner(System.in);
double[] array_score = new double[6];
for (int i = 0; i < 6; i++) {
System.out.println("What is the score given by the judge?");
array_score[i] = s.nextDouble();
}
return array_score;
}
public static void printArray(double[] j) {
for (int i = 0; i < 6; i++) {
System.out.println("The array is:" + j[i]);
}
}
}
double[] score = new double[6];
This line simply initializes an array of type double with 6 indexes allocated for it, with each resulting in 0 when printed out.
You could simply change the code in main to this, thus actually using the return value of the inputAllScores function.
public static void main(String[] args) {
double[] score = new double[6];
printArray(inputAllScores(score));
}
HTH
Related
Our assignment says we should "write the source code and test code for a function named sumArray that accepts an array of ints and returns the sum of all elements from the array".
I think I've got SumArray.java to return sum OK, but I'm struggling to apply my method to the test input. Any help please? TIA.
SumArray.java
package sumarray;
import java.util.Scanner;
public class SumArray {
private static int n, sum = 0;
public static int sumArray() {
Scanner s = new Scanner(System.in);
System.out.print("Enter no. of elements you want in array:");
n = s.nextInt();
int a[] = new int[n];
System.out.println("Enter the elements. (Press [return] after each one)");
for (int i = 0; i < n; i++) {
a[i] = s.nextInt();
sum = sum + a[i];
}
System.out.println("Sum:" + sum);
return sum;
}
public static void main(String[] args) {
sumArray();
}
}
SumArrayTest.java
package sumarray;
import org.junit.Test;
import static org.junit.Assert.*;
public class SumArrayTest {
public SumArrayTest() {
}
/**
* Test of main method, of class SumArray.
*/
#Test
public void testMain() {
System.out.println("main");
String[] args = null;
SumArray.main(args);
int[] intArray = new int[]{2, 3, 4};
int expectedResult = 9;
// int testResult = sumArray({2, 3, 4});
int testResult = SumArray sumArray(intArray);
assertEquals(expectedResult, testResult);
// fail("The test case is a prototype.");
}
}
Edit: I've tried to implement what's been suggested so far with some changes; really not sure of any of this is right; a lot of it is guesswork TBH.
package sumarray;
import java.util.Scanner;
public class SumArray {
private static int n, sum = 0;
public static int sumArray;
public static int sumArray(int[] arr) {
return sum;
}
public static SumArray input() {
Scanner s = new Scanner(System.in);
System.out.print("Enter no. of elements you want in array:");
n = s.nextInt();
int a[] = new int[n];
System.out.println("Enter the elements. (Press [return] after each one)");
for (int i = 0; i < n; i++) {
a[i] = s.nextInt();
sum = sum + a[i];
}
System.out.println("Sum:" + sum);
return new SumArray();
}
public static void main(String[] args) {
SumArray result = input();
System.out.println(result.sumArray(SumArray));
}
}
package sumarray;
import org.junit.Test;
import static org.junit.Assert.*;
public class SumArrayTest {
public SumArrayTest() {
}
#Test
public void testSumArray() {
System.out.println("main");
String[] args = null;
int[] intArray = new int[]{2, 3, 4};
int expectedResult = 9;
assertEquals(expectedResult, SumArray.sumArray(intArray));
// fail("The test case is a prototype.");
}
}
The only error I'm seeing currently is 'cannot find symbol' for SumArray in main.
package sumarray;
import java.util.Scanner;
public class SumArray {
private static int n, sum = 0;
public static int sumArray() {
Scanner s = new Scanner(System.in);
System.out.print("Enter no. of elements you want in array:");
n = s.nextInt();
int a[] = new int[n];
System.out.println("Enter the elements. (Press [return] after each one)");
for (int i = 0; i < n; i++) {
a[i] = s.nextInt();
sum = sum + a[i];
}
System.out.println("Sum:" + sum);
return sum;
}
public static void main(String[] args) {
sumArray();
}
}
The above is the original code you posted. Now, you say you get the correct output. Yes, here you do:
package sumarray;
import java.util.Scanner;
public class SumArray {
private static int n, sum = 0;
public static int sumArray() {
Scanner s = new Scanner(System.in);
System.out.print("Enter no. of elements you want in array:");
n = s.nextInt();
int a[] = new int[n];
System.out.println("Enter the elements. (Press [return] after each one)");
for (int i = 0; i < n; i++) {
a[i] = s.nextInt();
sum = sum + a[i];
}
System.out.println("Sum:" + sum);
return sum;
}
public static void main(String[] args) {
sumArray(); // this one will return the correct answer
sumArray(); // this one will not
}
}
The second one will return wrong data, because you don't reset the value of sum.
You should split the tasks: sumArray should receive an array, and should return the sum of the elements. Either you should change the name of the method, or change the implementation, that is what Mahmoud told you.
package sumarray;
import java.util.Scanner;
public class SumArray {
private static Scanner scan = new Scanner(System.in); // create this on class level, not every execution of your method
public static int[] buildArray(int elements) {
int[] arr = new int[elements];
for ( int i = 0; i < elements; i++ ) {
System.out.println("Enter element nr: " + (i+1));
arr[i] = scan.nextInt();
}
return arr;
}
public static int sumArray(int[] input) {
int sum = 0; // don't use a class level one. especially not a static one, it's value could be altered by another thread
for ( int in : input ) { // iterate over the array and add the values
sum += in; // this should be in -> each iteration we add the value of in (the element of the array) to sum
}
return sum;
}
public static void main(String[] args) {
System.out.println("Provide the size of the array: ");
int param = scan.nextInt();
int[] array = buildArray(param);
int result = sumArray(array);
System.out.println("The sum of the array is: " + result);
}
}
This approach will land you with far lesser issues. It also doesn't have static variables like n and sum in your class that might lead to wrong results.
The main() method is the entry point into the application, you shouldn't test the main() method. Instead, you should test the sumArray() method and compare the expected Vs. the actual returned value from the method.
As a side note, you can better pass the input array to the sumArray() method as a parameter instead of reading it from System.in within the method body.
So your method signature can look like this:
public static int sumArray(int[] arr). The client code which uses this method, which is the main method in your case (or the unit test) can pass the array without bothering the method how this input array was got.
I am writing a program that takes in the number of ingredients. The prog
This is my code:
import java.util.Scanner;
public class Restaurant {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int count = scan.nextInt();
}
Change this sortCalories function to the one below. Also you need to pass price array as second parameter like this sortCalories(calories,price, ingredientName);:
public static void sortCalories(double[] calories,double[] price, String[] ingredientName) {
double temp;
String temp1;
for (int p=0; p<calories.length; p++) {
for (int j=p+1; j<calories.length; j++) {
if(calories[p]/price[p]>calories[j]/price[j]) {
temp = calories[p];
calories[p] = calories[j];
calories[j] = temp;
temp = price[p];
price[p] = price[j];
price[j] = temp;
temp1 = ingredientName[p];
ingredientName[p] = ingredientName[j];
ingredientName[j] = temp1;
}
}
}
}
I've been trying with this problem but couldn't wrap my head around it..
"Create a java method int [] roundoff (ArrayList input) that returns a new integer array containing all the input doubles correctly rounded off to integers."
This is where I got so far:
package javaProblem;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;
public class TowMethods {
public static int[] roundOff(ArrayList<Double> input) {
int [] iL=new int[input.size()];
for (double i:iL) {
//input.get(i);
int n=(int) Math.round(i) ;
iL[n]=n;
}
System.out.print(Arrays.toString(iL));
return (iL);
}
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
ArrayList<Double> input1 = new ArrayList<Double>();
input1.add(2.3);
input1.add(1.3);
input1.add(3.35);
/* for (int i = 0; i < 3; i++) {
double num = keyboard.nextDouble();
input.add(num);
}*/
int[] iList = roundOff(input1);
System.out.println(Arrays.toString(iList));
}
}
for (int i = 0; i < input.size(); i++) {
iL[i] = (int)(Math.round(input.get(i)));
}
Instead of your loop in roundOff method
Please try to use meaningful names when you name your variables. Also inside the roundOff method instead of the foreach loop use a classic for loop and don't iterate through the freshly created integer array but over the ArrayList which you take as a parameter.
Here is the possible solution:
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class TowMethods {
public static int[] roundOff(ArrayList<Double> inputs) {
int [] integers=new int[inputs.size()];
for (int i=0; i < inputs.size(); i++) {
integers[i] = (int) Math.round(inputs.get(i));
}
return integers;
}
public static void main(String[] args) {
// Scanner keyboard = new Scanner(System.in);
ArrayList<Double> inputs = new ArrayList<Double>();
inputs.add(2.3);
inputs.add(1.3);
inputs.add(3.35);
/*
for (int i = 0; i < 3; i++) {
double num = keyboard.nextDouble();
inputs.add(num);
}
*/
int[] iList = roundOff(inputs);
System.out.println(Arrays.toString(iList));
}
}
If you want to take the user input just uncomment the commented lines in the main method.
Use Math.rint() which properly rounds to the next int value.
double [] dbls = {2.4, 8.8, 22.23, 97.6};
int[] ints = new int[dbls.length];
for (int i = 0; i < dbls.length; i++) {
ints[i] = (int)Math.rint(dbls[i]);
}
System.out.println(Arrays.toString(dbls));
System.out.println(Arrays.toString(ints));
Prints
[2.4, 8.8, 22.23, 97.6]
[2, 9, 22, 98]
having a problem with my java program. I am a newbie to Java and just can't figure out what is exactly the issue with it. In short I've declared an array and a variable in main, I've created my method call and would like my array be passed into my method with the variable. I would then like the method to take my array and count the number of times my variable "8" occurs, get rid of the 8 out of the array and return a new smaller array back to main. Here is my code below. I feel as if I am just missing one block code any suggestions?
public class Harrison7b
{
public static void main(String [] args)
{
int[] arrayA = {2,4,8,19,32,17,17,18,25,17,8,3,4,8};
int varB = 8;
// Call with the array and variable you need to find.
int[] result = newSmallerArray(arrayA, varB);
for(int x = 0; x < arrayA.length; x++)
{
System.out.print(arrayA[x] + " ");
}
}
public static int[] newSmallerArray( int[] arrayA, int varB)
{
int count = 0;
for(int x = 0; x < arrayA.length; x++)
{
if(arrayA[x] == varB)
{
count++;
}
}
int [] arrayX = new int[arrayA.length - count];
for(int B = 0; B < arrayA.length; B++)
{
if(arrayA[B] != varB)
{
}
}
return arrayX;
}
}
you do not actually need to return the array because when you pass an array to a method you also pass its memory address meaning its the same address that you change so, it will also change the arraysA of main method because you are just changing the values of the same memory adress
import java.util.*;
public class Help
{
public static void main(String[] args)
{
ArrayList<Integer> arraysA = new ArrayList<Integer>();
arraysA.add(Integer.valueOf(2));
arraysA.add(Integer.valueOf(4));
arraysA.add(Integer.valueOf(8));
arraysA.add(Integer.valueOf(19));
arraysA.add(Integer.valueOf(32));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(18));
arraysA.add(Integer.valueOf(25));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(8));
arraysA.add(Integer.valueOf(3));
arraysA.add(Integer.valueOf(4));
arraysA.add(Integer.valueOf(8));
int varB=8;
newSmallerArray(arraysA,varB);
for(Integer i:arraysA)
{
System.out.println(i);
}
}
public static void newSmallerArray(ArrayList<Integer> arraysA,int varB)
{
for(int i=0;i<arraysA.size();++i)
{
if(Integer.valueOf(arraysA.get(i))==varB)
{
arraysA.remove(i);
}
}
}
}
Try this code it will not require for loop:
List<Integer> list = new ArrayList<Integer>(Arrays.asList(arrayA));
list.removeAll(Arrays.asList(8));
arrayA = list.toArray(array);
I want to pass the result of this method.
static public int[][] scanCube(Cube c){
int counter0 = 0;
Scanner in = new Scanner(System.in);
counter0 = 0;
while(counter0 < 4){
cube[BOTTOM][counter0] = Integer.parseInt(in.nextLine());
counter0++;
}
return cube;
}
To this constructor so that I can call the method above in main.
private Cube(int [][] Scancube){
cube = new int[Scancube.length][];
for(int i = 0; i < Scancube.length; i++){
cube[i] = Arrays.copyOf(Scancube[i], Scancube[i].length);
}
}
So I can use this in main like this.
public static void main(String[] args) {
Cube c = new Cube();
Cube.scanCube(c);
System.out.println(c);
Cube.solve(c);
}
int[][] value= Cube.scanCube(c);
System.out.println(value);
Cube.solve(value);
Try like this, as you need to store the value first in the variable of the type you are using then you can pass the variable as a input for your next method.