not reversing order

Question about the task

In decreasing order

Java Syntax, Level 7, Lesson 12

Under discussion

my sort method is isn't flipping the order. Any thoughts?

package com.codegym.task.task07.task0728; import java.io.BufferedReader; import java.io.InputStreamReader; import java.util.*; /* In decreasing order */ public class Solution { public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); int[] array = new int[20]; for (int i = 0; i < 20; i++) { array[i] = Integer.parseInt(reader.readLine()); } sort(array); for (int x : array) { System.out.println(x); } } public static void sort(int[] array) { //write your code here Arrays.sort(array); int[] arr = new int[20]; for(int i = 0; i < 20; i++){ arr[i] = array[19-i]; } array = arr; } }

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Hardik

Level 11 , Ahmedabad, India

24 April 2019, 09:29

for (int i = numbers.length - 1; i > 0; i--) { for (int j = 0; j < i; j++) { /* Compare the elements in pairs. If they are not in the right order, then swap them */ if (numbers[j] < numbers[j + 1]) { int tmp = numbers[j]; numbers[j] = numbers[j + 1]; numbers[j + 1] = tmp; } } }

Louis

Level 17 , New York, United States

5 April 2019, 00:20

When you call "sort(array)", array is being passed by value, so when you assign arr to array in your sort method, you are actually assigning arr to a copy of the reference to the array you passed in, that is why the order of the original array's elements were not changed. Look up passing by value and passing by reference.

Guadalupe Gagnon

Level 37 , Tampa, United States

4 April 2019, 21:18

Not something that I have come across yet but it looks like when you pass an object like this to a method, you can change the data inside the object around to your hearts content, but you can not assign it a new object. Well you can assign it a new object, but that assignment is lost when the method concludes. It took a little testing to come to this conclusion. Modify you code like this and run it to see what is going on:

public class Solution {
    public static void main(String[] args) throws Exception {
        //BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int[] array = {10,13,345,1,3,1,4,54,3,67,68,4,2,34,12,34,21,8,65,90};
        /*for (int i = 0; i < 20; i++) {
            array[i] = Integer.parseInt(reader.readLine());
        }*/

        sort(array);
        System.out.println("Outside Method:\n" + Arrays.toString(array));
        /*for (int x : array) {
            System.out.println(x);
        }*/
    }

    public static void sort(int[] array) {
        //write your code here
        Arrays.sort(array);
        System.out.println("Inside Method after Arrays.sort:\n" + Arrays.toString(array));
        int[] arr = new int[20];
        for(int i = 0; i < 20; i++){
            arr[i] = array[19-i];
        }
        array = arr;
        System.out.println("Inside method after arr assignment:\n" + Arrays.toString(array));

    }
}

I printed to screen the 'array' object at three different points in the code. What you need to do is actually swap the elements around, not assign it to a new array.