I ve got the following code using arrays to find some prim numbers. However, when trying to compile my user class PalindromeArrayUser it says - "Constructor in class cannot be applied to given types"
required: int. found: no arguments. reason: actual and formal arguments lists differ in length.
However, I have passed to the constructer an int value (the same way it was designed in my blueprint). I don't quite get where the problem comes from. Thanks.
Here are my two classes
public class PalindromeArray
{
int arrLength;
public PalindromeArray(int InputValue)
{
arrLength = InputValue;
}
int arr[] = new int[arrLength];
boolean check[] = new boolean [arrLength];
public void InitializeArray()
{
for (int k = 2; k < arr.length; k++)
{
arr[k] = k;
check[k] = true;
}
}
public void primeCheck()
{
for (int i = 2; i < Math.sqrt(arr.length - 1); i++ )
{
if (check[i] == true)
{
for (int j = 2; j < arr.length; j++)
{
if (j % i == 0)
{
check[j] = false;
check[i] = true;
}
}
}
}
}
public void PrintArray()
{
for (int k = 2; k < arr.length; k++)
{
if ((!check[k]) == false)
System.out.println(arr[k]);
}
}
}
And this is my User class where the problem comes from. The class above compiles fine.
import java.io.*;
public class PalindromeArrayUser extends PalindromeArray
{
public static void main(String argv[]) throws IOException
{
BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Please enter the upper bound.");
String line = input.readLine();
int InputUser = Integer.parseInt(line);
// this is where I pass the same int type as I
// constructed it
PalindromeArray palindrome = new PalindromeArray(InputUser);
palindrome.InitializeArray();
palindrome.primeCheck();
palindrome.PrintArray();
}
}
when you create a constructor for a class, there won't be any default constructor created for that class. so if you extend that class and if the subclass tries to call the no-arg constructor of its super class then there will be an compile-time error.
to demonstrate:
class Parent {
int i;
public Parent(int i) {
this.i=i;
}
}
class Child extends Parent {
int j;
public Child(int i, int j) {
super(i);
this.j=j;
}
public Child(int j) {
// here a call to super() is made, but since there is no no-arg constructor
// for class Parent there will be a compile time error
this.j=j;
}
}
EDIT:
to answer your question do this, don't assign the value arrLength to arr[] and check[] as arrLength would be 0 at that time.
so just declare them like this
int arr[];
boolean check[];
and in the constructor after you assign the input to arrLength put these statements.
arr = new int[arrLength];
check = new boolean [arrLength];
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