Convert a List to a String with Separator in Java

This post will discuss how to convert a List to a String in Java. The solution should concatenate all items in the List to a String using a separator.

1. Using `String.join()` method

Since Java 8, you can use the String.join() method to join strings together using the specified separator. It only works on a List of type String. Here’s how the code will look like:

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<String> words = Arrays.asList("A", "B", "C", "D");

String sep = ", ";

String str = String.join(sep, words);

System.out.println(str);

}

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Output:

A, B, C, D

2. Using Stream API

Java 8 Stream API provides the joining collector that can concatenate the elements of a stream, separated by the specified delimiter. Its usage is demonstrated below:

import java.util.Arrays;

import java.util.List;

import java.util.stream.Collectors;

class Main

{

public static void main(String[] args)

{

List<Integer> input = Arrays.asList(1, 2, 3, 4);

String sep = ", ";

String str = input.stream().map(Object::toString)

.collect(Collectors.joining(sep));

System.out.println(str);

}

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Output:

1, 2, 3, 4

3. Using Apache Commons Lang

Apache Commons Lang StringUtils class provides the join() method which can concatenate list elements together with a specified separator, as shown below:

import org.apache.commons.lang3.StringUtils;

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<Integer> input = Arrays.asList(1, 2, 3, 4);

String sep = ", ";

String str = StringUtils.join(input, sep);

System.out.println(str);

}

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Output:

1, 2, 3, 4

4. Using Guava

If you prefer Guava to Apache Commons Lang, you might want to check out the flexible Joiner class. The following code demonstrates its usage by creating a Joiner, configuring the separator, and specifying the collection to be joined.

import com.google.common.base.Joiner;

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<Integer> input = Arrays.asList(1, 2, 3, 4);

String sep = ", ";

String str = Joiner.on(sep).join(input);

System.out.println(str);

}

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Output:

1, 2, 3, 4

5. Using `toString()` method

If you just need to print the string representation of the list, you can do so by calling the toString() on your list. This is demonstrated below:

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<Integer> input = Arrays.asList(1, 2, 3, 4);

String str = input.toString();

System.out.println(str);

}

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Output:

[1, 2, 3, 4]

That’s all about converting a List to a String in Java.

Convert a List to a String with Separator in Java

1. Using String.join() method

2. Using Stream API

3. Using Apache Commons Lang

4. Using Guava

5. Using toString() method

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1. Using `String.join()` method

5. Using `toString()` method