Assigning multiple values to multiple variables in a single line

Question

I'm trying to write the Java equivalent of the following Python Inversion-Sort algorithm:

import numpy as np



def main(items):



    for i in range(1, len(items)):

        j = i

        while j > 0 and items[j] < items[j-1]:

            items[j], items[j-1] = items[j-1], items[j]

            j -= 1



    print(items)



main(np.array([4, 78, 23, 24, 56, 7, 9]))

This is the Java version:

import java.util.Arrays;



public class Sorters {



    public static void main(String args[]) {



        Sorters sort = new Sorters();

        int[] items = {4, 78, 23, 24, 56, 7, 9};

        sort.insertionSort(items);

    }



    public void insertionSort(int[] items) {



        for(int i=1 ; i<items.length ; i++) {

            int j = i;

            while(j>0 && items[j] < items[j-1]) {

                items[j] = items[j-1]; // These two lines are

                items[j-1] = items[j]; // causing the error

                j -=1;

            }

        }

    System.out.println("Sorted array: " + Arrays.toString(items));

    } 

}

I've narrowed the issue down to the two lines that are commented as such, above (in the Java method).

If I give the Python function this array:

[4, 78, 23, 24, 56, 7, 9]

(for example), everything works fine. However, if I give the same array to the Java method, I get this in return:

[4, 78, 78, 78, 78, 78, 78]

.

Could someone tell me how to write the Java equivalent of Python's

items[j], items[j-1] = items[j-1], items[j]

? Explanations welcomed. Thanks.

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Answer 1

That's because you need to use a temp variable to store one of the values when you swap between the items[j] with items[j-1]. It should be something like that:

int temp = items[j];
items[j] = items[j-1];
items[j-1] = temp;

What happens is that you lose the original value so each iteration of the loop you get to copy into items[j] the value of items[j-1].

That's how you got your output.

Assigning multiple values to multiple variables in a single line

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