/*************************************************************************

 *  Compilation:  javac Shuffle.java

 *  Execution:    java Shuffle N < california-gov.txt

 *  Dependencies: StdIn.java

 *

 *  Reads in N lines of text, shuffles them, and print them in random order.

 *  Uses Knuth's shuffling shuffle.

 *

 *  The file california-gov.txt contains a list of the 135

 *  candidates in the October 7, 2003 California governor's runoff

 *  election. The file cards.txt contains a list of 52 playing cards.

 *

 *

 *  % java Shuffle 5 < california-gov.txt

 *  Iris Adam

 *  Douglas Anderson

 *  Alex-St. James

 *  Angelyne

 *  Brooke Adams

 *

 *  % java Shuffle 5 < cards.txt

 *  Four of Clubs

 *  Six of Clubs

 *  Three of Clubs

 *  Deuce of Clubs

 *  Five of Clubs

 *

 *

 *************************************************************************/

public class Shuffle { 

    // swaps array elements i and j

    public static void exch(String[] a, int i, int j) {

        String swap = a[i];

        a[i] = a[j];

        a[j] = swap;

    }

    // take as input an array of strings and rearrange them in random order

    public static void shuffle(String[] a) {

        int N = a.length;

        for (int i = 0; i < N; i++) {

            int r = i + (int) (Math.random() * (N-i));   // between i and N-1

            exch(a, i, r);

        }

    }

    // take as input an array of strings and print them out to standard output

    public static void show(String[] a) {

        for (int i = 0; i < a.length; i++) {

            System.out.println(a[i]);

        }

    }

    public static void main(String[] args) {

        int N = Integer.parseInt(args[0]);

        String[] a = new String[N];

        // read in data

        for (int i = 0; i < N; i++) {

            a[i] = StdIn.readLine();

        }

        // shuffle array and print permutation

        shuffle(a);

        show(a);

        System.out.println();

        // do it again

        shuffle(a);

        show(a);

    }

}

import java.util.ArrayList;

import java.util.Random;

public class J718{

    public static void main(String[]args){

        int[][]m={{1,2},{3,4},{5,6},{7,8},{9,10}};

        /*int N = m.length;

        for (int i = 0; i < N; i++) {

            int r = i + (int) (Math.random() * (N-i));   // between i and N-1

            System.out.print("{"+m[r][0]+","+m[r][1]+"} ");*/

         shuffle(m);

    }

    public static void shuffle(int[][]m){

        /*int N = m.length;

        for (int i = 0; i < N; i++) {

            int r = i + (int) (Math.random() * (N-i));   // between i and N-1

            System.out.print("{"+m[r][0]+","+m[r][1]+"} ");*/

        int n = m.length;

        Random rand = new Random();

        int[] p=new int[5];

        boolean[] bool = new boolean[n];

        int num =0;

        for (int i = 0; i<5; i++){

            do{

                //如果产生的数相同继续循环

                num = rand.nextInt(n);    

            }while(bool[num]);

            bool[num] =true;

            p[i]=num;

        }

        for(int j=0;j<n;j++)

        System.out.println ("{"+m[p[j]][0]+","+m[p[j]][1]+"} ");

    }

}