I want to find the max element in a 2-D array using Java Stream. Note: The elements in the List is stored as String.

Like this:

private static final List<List<String>> myList = Arrays.asList(
    Arrays.asList("1", "3", "99", "2", "14", "2"),
    Arrays.asList("111", "7", "199", "92", "14", "20"),
    Arrays.asList("10", "31", "9", "21", "243", "432"),
    Arrays.asList("31", "13", "999", "5", "41", "222"),
    Arrays.asList("10", "31", "401", "42", "11", "77")
);

I am expecting an int/Integer value as output(999 in this case).

CodePudding user response：

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Optional;

/* finding max of 2D array where int elements 
 * are in String*/
public class MaxOf2DArray {
    
 public int findMax(List<List<String>> list){
    Comparator<Integer> cmp =( i1, i2)->{return i1.compareTo(i2);}; 
    Optional<Integer> maxNumber= list.stream().flatMap(List::stream).map(k->Integer.valueOf(k)).max(cmp);
    
    return maxNumber.orElse(0);
     
 }
 public static void main(String[]args){
      List<List<String>> myList = Arrays.asList(
                Arrays.asList("1", "3", "99", "2", "14", "2"),
                Arrays.asList("111", "7", "199", "92", "14", "20"),
                Arrays.asList("10", "31", "9", "21", "243", "432"),
                Arrays.asList("31", "13", "999", "5", "41", "222"),
                Arrays.asList("10", "31", "401", "42", "11", "77")
            );
     MaxOf2DArray maxOf2DArray= new MaxOf2DArray();
     
     System.out.println(maxOf2DArray.findMax(myList));
     
     
 }
}