Guava Chars.concat() method in Java

This post will discuss about concatenate char arrays in Java using Guava Chars.concat() method.

Sometimes, you might need to concatenate multiple arrays into one. For example, you might want to join the characters of your first name and last name into a single array, or append some punctuation marks to an array of letters. How do you do that in Java?

You might think of using the + operator to concatenate char arrays, but that won’t work. The + operator only works for String objects, not for primitive types like char. If you try to use it, you will get a compiler error.

One option is to use a StringBuilder object, which is a mutable sequence of characters that can be modified and appended. You can loop through each char array and append its elements to the StringBuilder, then convert it to a char array using the toString() and toCharArray() methods. For example, this code will work:

import java.util.Arrays;

class Main {

public static void main(String[] args) {

char[] firstName = {'J', 'o', 'h', 'n'};

char[] lastName = {'D', 'o', 'e'};

StringBuilder sb = new StringBuilder();

for (char c : firstName) {

sb.append(c);

}

for (char c : lastName) {

sb.append(c);

}

char[] fullName = sb.toString().toCharArray();

System.out.println(Arrays.toString(fullName)); // [J, o, h, n, D, o, e]

}

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However, this approach is not very efficient or elegant. You have to create a new object, iterate through each array, and perform conversions between String and char[]. There must be a better way, right?

Fortunately, there is. If you are using the Guava library, which is a collection of useful utilities and common APIs for Java, you can use the Chars.concat() method to concatenate char arrays in a single line of code. The Chars class is a utility class for primitive type char that provides static methods for various operations on char arrays. The concat() method takes one or more char arrays as parameters and returns a new char array that contains all the elements of the given arrays in their original order. The method has the following syntax:

1	public static char[] concat(char[]… arrays)

The parameter arrays is a varargs of char arrays to be concatenated by this method. The method throws a NullPointerException if any of the arrays is null. Here is an example of using the method to concatenate two arrays:

import com.google.common.primitives.Chars;

import java.util.Arrays;

class Main {

public static void main(String[] args) {

char[] firstName = {'J', 'o', 'h', 'n'};

char[] lastName = {'D', 'o', 'e'};

char[] fullName = Chars.concat(firstName, lastName);

System.out.println(Arrays.toString(fullName)); // [J, o, h, n, D, o, e]

}

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As you can see, the concat() method is much simpler and cleaner than using a StringBuilder. It also handles empty arrays gracefully, and preserves the order of the elements in the original arrays. For example:

import com.google.common.primitives.Chars;

import java.util.Arrays;

class Main {

public static void main(String[] args) {

char[] arr1 = {'a', 'b'};

char[] arr2 = {};

char[] arr3 = {'c'};

char[] arr4 = {'d', 'e'};

char[] result = Chars.concat(arr1, arr2, arr3, arr4);

System.out.println(Arrays.toString(result)); // [a, b, c, d, e]

}

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The concat() method is also faster than using a StringBuilder. According to the Guava source code, the concat() method uses System.arraycopy() under the hood, which is a native method that copies an array from one memory location to another. This method is optimized for performance and avoids unnecessary object creation and conversions.

So, if you are looking for a quick and efficient way to concatenate char arrays in Java, we highly recommend using the Guava Chars.concat() method. It will save you time and code lines, and make your code more readable and maintainable.

Guava Chars.concat() method in Java

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