Join the collection elements by a separator using streams

Below snippet join the collection elements by a delimiter using streams.

public static String join(final Collection<?> collection, final String delimiter) {
	if (collection == null) {
		return "";
	}

	Collector<CharSequence, ?, String> collector = Collectors.joining();

	if (delimiter != null) {
		collector = Collectors.joining(delimiter);
	}

	return collection.stream().map(String::valueOf).collect(collector);
}

 

‘Stream#map’ method is used to convert each element of the collection to its string representation, and the joining method of the Collectors class concatenates the strings using the specified delimiter.

 

Find the below working application.

 

CollectionElementsJoinDemo.java

package com.sample.app.collections;

import java.util.Arrays;
import java.util.Collection;
import java.util.stream.Collector;
import java.util.stream.Collectors;

public class CollectionElementsJoinDemo {

	public static String join(final Collection<?> collection, final String delimiter) {
		if (collection == null) {
			return "";
		}

		Collector<CharSequence, ?, String> collector = Collectors.joining();

		if (delimiter != null) {
			collector = Collectors.joining(delimiter);
		}

		return collection.stream().map(String::valueOf).collect(collector);
	}

	public static void main(String[] args) {
		Collection<String> data = Arrays.asList("India", "China", "Sri Lanka", "Nepal");

		String result1 = join(data, ",");
		String result2 = join(data, "->");
		String result3 = join(data, ";");

		System.out.println("result1 : " + result1);
		System.out.println("result2 : " + result2);
		System.out.println("result3 : " + result3);

	}

}

 

Output

result1 : India,China,Sri Lanka,Nepal
result2 : India->China->Sri Lanka->Nepal
result3 : India;China;Sri Lanka;Nepal

 

 

 

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