How can I public the element in my question

Question

I'm going to output the object element, but it not successful to output the value to public. Anyone have some idea? I have tried to implement the following code.

import java.util.Scanner;

public class Qa {

    private static void qb(int left, int right) {

        int pivotIndex = left; //set first element as pivot
        int storeIndex = pivotIndex + 1;

        for (int i = pivotIndex + 1; i <= right; i++)
            if (element[i] < element[pivotIndex]) {
                swap(i, storeIndex);
                storeIndex++;
            }

        swap(pivotIndex, storeIndex - 1);
        printElement();

        //recursion
        if (storeIndex - 2 - left >= 1)
            qsort(left, storeIndex - 2);

        if (right - storeIndex >= 1)
            qsort(storeIndex, right);
    }

    private static void swap(int n1, int n2) {
        int tmp = element[n1];
        element[n1] = element[n2];
        element[n2] = tmp;
    }

    private static void printElement() {
        for (int i = 0; i < element.length; i++)
            System.out.print(element[i] + "  ");
        System.out.println("");
    }
}

I'm pretty sure you mean "Quicksort" instead of "Quest sort" in your title. :) — ihavenoidea, Nov 30 '20 at 16:37

Jimbo McHiggins · Answer 1 · 2020-11-30T16:43:24.897

If the goal is to access the element array as a class member it just needs to be defined as static and change element's initialization to the class member.

    public static int[] element;
    public static void main(String[] args) {
        int n;
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the number of the items you want to store: ");
        n = sc.nextInt();
        
        // This line must update element not create a local variable.
        element = new int[10];
        System.out.println("Enter the values: ");

        for(int i=0;i<n;i++) {
            element[i] = sc.nextInt();
        }

        printElement();
        qsort(0, element.length - 1);
    }

element's initialization must be changed from creating a new local variable to using the new class member. i.e. change

int[] element = new int[10];

to

element = new int[10];

If this is not done the other static methods will not have access to the data your scanner took in and will result in NullPointerExceptions.

Thanks. it can complete now but It show some error.`Enter the number of the items you want to store: 4 Enter the values: 36 44 23 11 Exception in thread "main" java.lang.NullPointerException at QuickSort.printElement(QuickSort.java:51) at QuickSort.main(QuickSort.java:18)` — erictc, Nov 30 '20 at 16:38
I've updated my answer to be more explicit about the change needed to `element`'s initialization. — Jimbo McHiggins, Nov 30 '20 at 16:44

score 0 · Answer 2 · answered Nov 30 '20 at 16:15

0

Add a parameter

printElement(element);

Update the method

private static void printElement(int[] element) {

Note: You can print with Arrays.toString as well

answered Nov 30 '20 at 16:15

OneCricketeer

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score 0 · Accepted Answer · answered Nov 30 '20 at 17:11

you can pass your array of values as parameter to your printElement method and then print the elements inside the array:

private static void printElement(int[] elements) {
    for (int i = 0; i < elements.length; i++)
        System.out.print(elements[i] + "  ");
    System.out.println("");
}

and pint:

printElement(element);
qsort(0, element.length - 1);
printElement(element);

How can I public the element in my question

3 Answers3