My Java random pick by index example.

JavaApplication1.java

package javaapplication1;

import java.util.*;

public class JavaApplication1 {

    public static void main(String[] args) {
    
        
        Random rand = new Random();
        
        List<Integer> lstNum = new ArrayList();
        List<Integer> lstSelectedNum = new ArrayList();
        
        //init list
        for (int i = 1; i < 9; i++) {
            lstNum.add(i);
        }
        
        //random select by index
        while (lstNum.size() > 0) {
            int index = rand.nextInt(lstNum.size());
            int selectedNum = (int)lstNum.toArray()[index];
        
            lstSelectedNum.add(selectedNum);
            lstNum.remove(index);   
        }
        
        //print all selected element
        for (int i = 0; i < lstSelectedNum.size(); i++) {
            System.out.println(lstSelectedNum.toArray()[i]);
        }
    }
}