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Member
Posts: 31,313
Joined: Mar 25 2009
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Nov 3 2020 10:09pm
Code

/*Program to generate 100 random numbers and then sort them from lowest to highest*/


package com.ferfykins.exercises;

import java.util.Arrays;
import java.util.Collections;
import java.util.Random;

public class Main {

public static void main(String[] args) {

Random ranNumber = new Random();


int[] myIntArray = new int[100];

for (int i = 0; i < myIntArray.length; i++) {
myIntArray[i] = ranNumber.nextInt(99);
}


Arrays.sort(myIntArray);

for (int numbers : myIntArray) {
System.out.println(numbers);
}

System.out.println("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$");

Collections.reverse(Arrays.asList(myIntArray));


for (int numbers : myIntArray) {
System.out.println(numbers);
}


}


}




So basically i create an array of 100 numbers, and then sort them from least to greatest.
NOW, i wanna reverse that, so it goes from greatest to least. but the Collections.reverse does not seem to be working.......
Member
Posts: 1,304
Joined: Jul 8 2012
Gold: 0.00
Nov 4 2020 09:53am
Collections.reverse requires a list, not an array.

Code
public static void main(String []args){

Random ranNumber = new Random();

Integer[] myIntArray = new Integer[100];

for (int i = 0; i < myIntArray.length; i++) {
myIntArray[i] = ranNumber.nextInt(99);
}

Arrays.sort(myIntArray);
System.out.println(Arrays.asList(myIntArray));

Collections.reverse(Arrays.asList(myIntArray));
System.out.println(Arrays.asList(myIntArray));
}


Note that int changed to Integer.

I advise you to check out documentation if your understanding of a function isn't in line with its output.

https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html

Trial in error in programming is rarely the solution, do your research : )

This article will explain why Integer is needed: https://www.w3schools.com/java/java_wrapper_classes.asp

This post was edited by Kippet on Nov 4 2020 10:01am
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