How to generate random non-repeating numbers in java:
Generate n non-repeating random numbers based on min and max. (Note: Range [min,max], n <= (max - min 1))
Idea:
0), put all possible numbers from min to max Enter a candidate List;
1), randomly generate index index (0 <= index <= (list.size()-1));
2), based on index Take a number from the List, list.get(index), and remove the element;
The code is as follows:
import java.util.ArrayList; import java.util.List; import java.util.Random; public class MyRandom { /** * 根據(jù)min和max隨機(jī)生成一個(gè)范圍在[min,max]的隨機(jī)數(shù),包括min和max * @param min * @param max * @return int */ public int getRandom(int min, int max){ Random random = new Random(); return random.nextInt( max - min + 1 ) + min; } /** * 根據(jù)min和max隨機(jī)生成count個(gè)不重復(fù)的隨機(jī)數(shù)組 * @param min * @param max * @param count * @return int[] */ public int[] getRandoms(int min, int max, int count){ int[] randoms = new int[count]; List<Integer> listRandom = new ArrayList<Integer>(); if( count > ( max - min + 1 )){ return null; } // 將所有的可能出現(xiàn)的數(shù)字放進(jìn)候選list for(int i = min; i <= max; i++){ listRandom.add(i); } // 從候選list中取出放入數(shù)組,已經(jīng)被選中的就從這個(gè)list中移除 for(int i = 0; i < count; i++){ int index = getRandom(0, listRandom.size()-1); randoms[i] = listRandom.get(index); listRandom.remove(index); } return randoms; } }
Java Math.random() method is used to return a random number, random The range of numbers is 0.0 =< Math.random < 1.0.
For more java knowledge, please pay attention to java basic tutorial.
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