2 Illustration To Merge Or Bring Together Multiple Listing Inwards Coffee - Tutorial

Sometimes, nosotros involve to merge multiple lists into i earlier performing whatever operation, tell Iteration or transformation. It's quite mutual to merge 2 lists, or combine them into a bigger listing in addition to in that place are multiple ways to exercise it. In this article, nosotros volition convey a expect at 2 unproblematic means to join 2 lists inwards Java, you lot tin farther extend that reckon to bring together whatever release of List or it's implementation e.g. ArrayList or LinkedList inwards Java. One means to merge multiple lists is past times using addAll() method of java.util.Collection class, which allows you lot to add together content of i List into around other List. By using addAll() method you lot tin add together contents from equally many List equally you lot want, it's best means to combine multiple List. One affair to recollect is that it too preserves the club on which objects from List are added, it genuinely appends at the halt of the collection. So if you lot add together List1 in addition to than List2, content of List1 volition come upward earlier elements of List2. You tin fifty-fifty purpose this technique to combine multiple List into a Set to take away whatever duplicates. 

Another means of merging ArrayList is using Apache Commons Collection, Apart from several goodies, similar creating matrimony of Set inwards Java,  it provides a ListUtils degree amongst a matrimony method, which tin survive used to exercise matrimony of 2 List inwards Java. Result of previous functioning in addition to this is same, It too preservers the club in addition to appends elements of minute List afterward elements of commencement List.

Java Code illustration to merge multiple List

create an ArrayList in addition to used addAll() method to append objects cast minute List. In minute way, nosotros induce got used ListUtils.union() method to combine 2 Lists.

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import org.apache.commons.collections.ListUtils;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

/**

 * Java plan to merge multiple List into a unmarried List using JDK in addition to opened upward source

 * Apache Commons library.

 *

 * @author Javin Paul

 */

public class MergeList {

    private static final Logger logger = LoggerFactory.getLogger(MergeList.class);

    public static void main(String args[]) {

      

        List hundreads = Arrays.asList(101,102,103);

        List thousands = Arrays.asList(1001,1002,1003);

   

        // merging 2 listing using gist Java

        List merged = new ArrayList(hundreads);

        merged.addAll(thousands);

      

        System.out.println("List 1 : " + hundreads);

        System.out.println("List 2 : " + thousands);

        System.out.println("Merged List : " + merged);

      

      

        // around other means to merge 2 listing inwards Java

        // using ListUtils from Apache common Collection

        merged = ListUtils.union(hundreads, thousands);

        System.out.println("Merged List using Apache Commons Collections: " + merged);

      

    }

  

}

Output:

List 1 : [101, 102, 103]

List 2 : [1001, 1002, 1003]

Merged List : [101, 102, 103, 1001, 1002, 1003]

Merged List using Apache Commons Collections: [101, 102, 103, 1001, 1002, 1003]

That's all on this tutorial virtually merging 2 List inwards Java using JDK in addition to Apache Commons Collections library. It's a really useful flim-flam in addition to tin survive useful inwards several cases. You tin fifty-fifty extend this reckon to exercise a Set of unique elements from multiple List equally well, addAll() method from Collection, accepts whatever Collection implementation including ArrayList, LinkedList etc.

Further Learning
Java Fundamentals: The Java Language past times Jim Wilson
Java Fundamentals: Collections
Head First Java

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