以升序对数组排序

Question

So I have this code right now. It runs, but it won't sort the array of numbers in ascending order and I don't know what I should do. I'm new to java so...

import javax.swing.JOptionPane;

public class ThirdClass
{
    public static void main (String args[]){

        int a = 0;
        int b;

        int numbers;
        int length = Integer.parseInt(JOptionPane.showInputDialog (null, "Input set size", JOptionPane.QUESTION_MESSAGE));
        int ctr = 1;
        int num[] = new int[length];

            for(int i = 0; i < length; i++){
            num[i] = Integer.parseInt(JOptionPane.showInputDialog (null, "Enter number " + ctr, JOptionPane.QUESTION_MESSAGE));
                    ctr++;
            }

            for(int i = 0; i < length; i++){
                for(int j = i+1; j < length; j++){
                        if(num[i]<num[j]){
                            a = num[i];
                            num[i] = num[j];
                            num[j] = a;
                        }
                    }
            }

            for(int i = 0; i < length; i++){
            JOptionPane.showMessageDialog (null, "Output: " + num[i] , "Value", JOptionPane.INFORMATION_MESSAGE);
            }
    }
}

Answer 1

You appear to be trying to do a bubble sort, but your logic is a bit off. Change your double for loop to this:

for (int i=0; i < length; ++i) {
    for (int j=1; j < (length-i); ++j) {
        if (num[j-1] > num[j]){
            a = num[j-1];
            num[j-1] = num[j];
            num[j] = a;
        }
    }
}

Answer 2

You don't need to change your complete logic. Just need to change sign less than to greater than Check below code.

for(int i = 0; i < length; i++){
                for(int j = i+1; j < length; j++){
                        if(num[i]>num[j]){
                            a = num[i];
                            num[i] = num[j];
                            num[j] = a;
                        }
                    }
            }