CODEWITHSUNDEEP
javacollectionsarraylist
Rapharlo
Rapharlo

Reputation: 89

Java: Exclude array index in shuffle

Is it possible to exclude array indexes in a shuffle?

My insight in this question:

   Array[0,1,2,3,4,5,6,7,8]
   Exclude Array index 2 and 7 in shuffle.
   Shuffle Array.
   Array[3,5,2,1,6,8,0,7,4]

This is my what I used in my shuffle:

List<Pokemon>list = Arrays.asList(pkm);
Collections.shuffle(list);

EDIT:

Thanks, @Jhanvi! I studied your code and it gave me some ideas. I tried to play around with yours and @Rohit Jain's codes and created a sample:

import java.util.Arrays;

    import java.util.Collections;
    import java.util.List;
    import java.util.ArrayList;

public class Example {

 public static void main(String[]args){
    String[] x = {"a","b","c","d","e","f","g","h"};
    List<String> list = new ArrayList<String>(Arrays.asList(x));
    System.out.println("Before shuffling, ArrayList contains : " + list);
    Object obj = list.remove(7);
    Object obj1 = list.remove(2);
    Collections.shuffle(list);
    list.add(2, obj1);
    list.add(7, obj);
    System.out.println("After shuffling, ArrayList contains : " + list);        
 }     
}

Annoyingly it gives me an error: cannot find symbol method add(int,java.lang.Object) on both my list.add().

I checked that there exists a .add(int,Object) method for List, thinking that it will work. What part did I miss?

Upvotes: 4

Views: 2063

Answers (2)

Jhanvi
Jhanvi

Reputation: 5139

You can try something like this: 

ArrayList arrayList = new ArrayList();
arrayList.add(0);
arrayList.add(1);
arrayList.add(2);
arrayList.add(3);
arrayList.add(4);
arrayList.add(5);
arrayList.add(6);
arrayList.add(7);
System.out.println("Before shuffling, ArrayList contains : " + arrayList);
Object obj = arrayList.remove(7); // remove by index!
Object obj1 = arrayList.remove(2);
Collections.shuffle(arrayList);
arrayList.add(2, obj1);
arrayList.add(7, obj);
System.out.println("After shuffling, ArrayList contains : " + arrayList);

Upvotes: 15

Eduardo
Eduardo

Reputation: 8392

You could create a shuffle yourself: just pick two indexes at random, making sure you exclude the ones you want to exclude, and swap the array elements in those positions. Repeat enough times.

Upvotes: 2

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