某筆試題（一）獲取20個隨機不重複的字符

import java.util.ArrayList;
import java.util.Random;


public class sort {
	
	public static void main(String[] args){
		
		System.out.println(get());
	}
	
	public static ArrayList<Character> get(){
		ArrayList<Character> list = new ArrayList<>(20);
		while(list.size() <= 20){
			
			//1.獲取隨機字符c
			char c = getRandomCharacter();
			
			//2.比較，ArrayList的indexOf方法是真的方便
			if (list.indexOf(c) == -1) {
				list.add(c);
			}
					
		}
		return list;
	}
	
	//獲取1-20的隨機數
	public static char getRandomCharacter(){
		String base = "qwertyuioplkjhgfdsazxcvbnm";
	
		return base.charAt(new Random().nextInt(26));
	}
}