CODEWITHSUNDEEP
java
Aaron
Aaron

Reputation: 11673

How to sort an array in reverse order using java?

package javaLearning;
import java.util.Arrays;
import java.util.Collections;

    public class myarray {

         public static void name() {
         String hello;
         hello = "hello, world";
         int hello_len = hello.length();
         char[] hello_array = new char[hello_len];
         hello.getChars(0, hello_len, hello_array, 0);
         Arrays.sort(hello_array, Collections.reverseOrder());
}

the "myarray" class is defiend in a main method of a testing class. why does it give me a compile error when I try reversing the array?

Upvotes: 5

Views: 14671

Answers (6)

Jagadeesh
Jagadeesh

Reputation: 2800

The first thing is that the code is not followed the standards of JAVA language. Class name should always starts with UPPER case, and sort() of Arrays should not take primitive list of values as a parameter. change the 'char' to 'Character' and then use Arrays.sort method

Upvotes: 0

Aravindan R
Aravindan R

Reputation: 3084

Collections.reverseOrder() returns a Comparator<Object>. And Arrays.sort with comparator doesn't work for primitives

This should work

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

public class MyArray {

    public static void name() {            
        String hello = "hello, world";
        char[] hello_array = hello.toCharArray();
        // copy to wrapper array
        Character[] hello_array1 = new Character[hello_array.length];
        for (int i = 0; i < hello_array.length; i++) {
           hello_array1[i] = hello_array[i];
        }
        // sort the wrapper array instead of primitives
        Arrays.sort(hello_array1, Collections.reverseOrder());                            
    }
}

Upvotes: 6

jtahlborn
jtahlborn

Reputation: 53694

Use Arrays.sort to sort in ascending order, then reverse the elements of the array (can be done inline with a simple loop).

Upvotes: 0

Jeff Foster
Jeff Foster

Reputation: 44706

The error I get (assuming the original post had some typos) is that Collections.reverseOrder() returns a Comparator<Object>.

Arrays.sort (with a compartor) is only defined for descendents of Object so doesn't work for primitive types.

Upvotes: 2

ewan.chalmers
ewan.chalmers

Reputation: 16235

haa is not defined in the code you have shown us. That is a compile error.

Upvotes: -1

krookedking
krookedking

Reputation: 2303

You forgot to declare haa = hello.getChars(0, hello_len, hello_array, 0);

Upvotes: 0

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