Concatenating List<String> to String in Java with Commas

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Question:

Java I have a List<String> data, I need you to use "," to concatenate it into a string

Answer:

In Java, you can concatenate a List<String> into a single String using the String.join() method or using a StringBuilder. Here are two common approaches:

Using String.join()

If you are using Java 8 or later, you can use the String.join() method, which is straightforward and concise:

import java.util.List;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        List<String> data = Arrays.asList("apple", "banana", "cherry");
        
        // Concatenate the list into a single string with commas
        String result = String.join(",", data);
        
        System.out.println(result); // Output: apple,banana,cherry
    }
}

Using StringBuilder

If you are using an earlier version of Java or prefer a more manual approach, you can use a StringBuilder:

import java.util.List;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        List<String> data = Arrays.asList("apple", "banana", "cherry");
        
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < data.size(); i++) {
            sb.append(data.get(i));
            if (i < data.size() - 1) {
                sb.append(","); // Append comma if not the last element
            }
        }
        
        String result = sb.toString();
        System.out.println(result); // Output: apple,banana,cherry
    }
}

Both methods will give you the same result, so you can choose the one that best fits your needs or coding style.

If you prefer to use Java's open-source libraries for concatenating a list of strings with commas, you can leverage the Apache Commons Lang library or the Guava library. Here's how you can achieve this using these libraries:

Using Apache Commons Lang:

  1. Add Apache Commons Lang Dependency: Make sure you have Apache Commons Lang added to your project dependencies. You can add the following Maven dependency to your pom.xml file:

    <dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

  2. Concatenating List<String> with Apache Commons Lang:

    import org.apache.commons.lang3.StringUtils;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> list = List.of("apple", "banana", "cherry");
        String result = StringUtils.join(list, ", ");
        System.out.println(result);
    }
}

Using Guava Library:

  1. Add Guava Dependency: Include the Guava library in your project. You can add the following Maven dependency to your pom.xml file:

    <dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>30.1-jre</version>
</dependency>

  2. Concatenating List<String> with Guava:

    import com.google.common.base.Joiner;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> list = List.of("apple", "banana", "cherry");
        String result = Joiner.on(", ").join(list);
        System.out.println(result);
    }
}

By using these libraries, you can achieve the concatenation of a list of strings with commas in a concise and efficient manner. Choose the library that best fits your project requirements and coding preferences.

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