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How to determine if all elements are the same in a Java List?
You can check all elements of a list to be same using streams easily in two steps −
Get the first element.
String firstItem = list.get(0);
Iterate the list using streams and use allMatch() method to compare all elements with the first element.
boolean result = list.stream().allMatch(i -> i.equals(firstItem));
Example
Following is the example showing the use of streams to check elements of the list being same −
package com.tutorialspoint;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
public class CollectionsDemo {
public static void main(String[] args) {
List<String> list = new ArrayList<>(Arrays.asList("A", "A", "A", "A", "A"));
System.out.println("List: " + list);
String firstItem = list.get(0);
boolean result = list.stream().allMatch(i -> i.equals(firstItem));
System.out.println("All elements are same: " + result);
list.add("B");
System.out.println("List: " + list);
result = list.stream().allMatch(i -> i.equals(firstItem));
System.out.println("All elements are same: " + result);
}
}Output
This will produce the following result −
List: [A, A, A, A, A] All elements are same: true List: [A, A, A, A, A, B] All elements are same: false
Updated on: 09-May-2022
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