The CollectonsUtils.union() method is used to get the union of two lists. Consider we have two lists list1 and list2, which have different elements.
package com.javatute;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.collections4.CollectionUtils;
public class CollectionsUtilIsUnionCollection {
public static void main(String[] args) {
// Create first list
List<String> list1 = new ArrayList<>();
// add some element
list1.add("John");
list1.add("Mark");
list1.add("Smith");
list1.add("Twin");
// create second list
List<String> list2 = new ArrayList<>();
// add some element
list2.add("John");
list2.add("Mark");
list2.add("Smith");
list2.add("Twin");
list2.add("James");
System.out.println(CollectionUtils.union(list1, list2));
}
}
Output – [James, Smith, John, Mark, Twin]
Note – We need to add maven dependency in order to use CollectionUtils class.
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.4</version>
</dependency>
That’s all about CollectionUtils union() Example in Java.
See CollectionUtils union() method docs.
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