/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
 
	// The main function that prints all combinations of size r
// in arr[] of size n. This function mainly uses combinationUtil()
static void printCombination(String arr[], int n, int r)
{
    // A temporary array to store all combination one by one
    String[] data = new String[r];
 
    // Print all combination using temprary array 'data[]'
    combinationUtil(arr, data, 0, n-1, 0, r);
}
 
/* arr[]  ---> Input Array
   data[] ---> Temporary array to store current combination
   start & end ---> Staring and Ending indexes in arr[]
   index  ---> Current index in data[]
   r ---> Size of a combination to be printed */
static void combinationUtil(String arr[], String data[], int start, int end, int index, int r)
{
    // Current combination is ready to be printed, print it
    if (index == r)
    {
        for (int j=0; j<r; j++)
            System.out.printf("%s ", data[j]);
        System.out.printf("\n");
        return;
    }
 
    // replace index with all possible elements. The condition
    // "end-i+1 >= r-index" makes sure that including one element
    // at index will make a combination with remaining elements
    // at remaining positions
    for (int i=start; i<=end && end-i+1 >= r-index; i++)
    {
        data[index] = arr[i];
        combinationUtil(arr, data, i+1, end, index+1, r);
    }
}
	public static void main (String[] args) throws java.lang.Exception
	{
		// Driver program to test above functions
    String arr[] = {"A","B","C","D","E","F","G"};
    int r = 3;
    int n = arr.length;
    printCombination(arr, n, r);
	}
}

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