Collections. shuffle () Method Instance parsing,

Collections. shuffle () Method Instance parsing,

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Java. util. Collections class has a static shuffle () method, as follows:

1) static void shuffle (List <?> List) use the default random source to replace the list. The probability of all replications is roughly equal.

2) static void shuffle (List <?> List, Random rand) Replace the specified list with the specified Random source. All replications are generally equal. It is assumed that the Random source is fair.

In other words, like shuffling, the original order is randomly disrupted.

NOTE: If an integer array is given, use the Arrays. asList () method to convert it into a collection class. There are two ways:

1) Use List <Integer> list = ArrayList (Arrays. asList (ia) and shuffle () to disrupt the order of the underlying array.

2) Use List <Integer> list = Arrays. aslist (ia), and then use shuffle () to disrupt the order of the underlying array. The code example is as follows:

package ahu;import java.util.*;public class Modify {public static void main(String[] args){Random rand=new Random(47);Integer[] ia={0,1,2,3,4,5,6,7,8,9};List<Integer> list=new ArrayList<Integer>(Arrays.asList(ia));System.out.println("Before shufflig: "+list);Collections.shuffle(list,rand);System.out.println("After shuffling: "+list);System.out.println("array: "+Arrays.toString(ia));List<Integer> list1=Arrays.asList(ia);System.out.println("Before shuffling: "+list1);Collections.shuffle(list1,rand);System.out.println("After shuffling: "+list1);System.out.println("array: "+Arrays.toString(ia));}}

The running result is as follows:

Before shufflig: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] After shuffling: [3, 5, 2, 0, 7, 6, 1, 4, 9, 8] array: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] Before shuffling: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] After shuffling: [8, 0, 5, 2, 6, 1, 4, 9, 3, 7] array: [8, 0, 5, 2, 6, 1, 4, 9, 3, 7] 

In the first case, Arrays. the asList () output is passed to the ArrayList () constructor, which creates an ArrayList that references the ia element. Therefore, if these references are disrupted, the array is not modified. However, if you directly use the results of Arrays. asList (ia), this will change the ia sequence. It is important to realize that the List object generated by Arrays. asList () uses the underlying array as its physical implementation. As long as your operation will modify the List and you do not want the original array to be modified, you should create a copy in another container.

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