Java Guava | Doubles.concat() method with Examples

Last Updated : 11 Jul, 2025
The concat() method of Doubles Class in the Guava library is used to concatenate the values of many arrays into a single array. These double arrays to be concatenated are specified as parameters to this method.
For example: concat(new double[] {a, b}, new double[] {}, new double[] {c} returns the array {a, b, c}.
Syntax: 
public static double[] concat(double[]... arrays)
Parameter: This method accepts arrays as parameter which is the double arrays to be concatenated by this method. Return Value: This method returns a single double array which contains all the specified double array values in its original order. Below programs illustrate the use of concat() method: Example 1: Java 
// Java code to show implementation of
// Guava's Doubles.concat() method

import com.google.common.primitives.Doubles;
import java.util.Arrays;

class GFG {

    // Driver's code
    public static void main(String[] args)
    {
        // Creating 2 Double arrays
        double[] arr1 = { 1.2, 2.3, 3.5, 4.4, 5.1 };
        double[] arr2 = { 6.2, 2.1, 7.2, 0.4, 8.7 };

        // Using Doubles.concat() method to combine
        // elements from both arrays into a single array
        double[] res = Doubles.concat(arr1, arr2);

        // Displaying the single combined array
        System.out.println(Arrays.toString(res));
    }
}
Output: 
[1.2, 2.3, 3.5, 4.4, 5.1, 6.2, 2.1, 7.2, 0.4, 8.7]
Example 2: Java 
// Java code to show implementation of
// Guava's Doubles.concat() method

import com.google.common.primitives.Doubles;
import java.util.Arrays;

class GFG {

    // Driver's code
    public static void main(String[] args)
    {
        // Creating 4 Double arrays
        double[] arr1 = { 1.2, 2.3, 3.4 };
        double[] arr2 = { 4.5, 5.6 };
        double[] arr3 = { 6.4, 7.6, 8.7 };
        double[] arr4 = { 9.7, 0.8 };

        // Using Doubles.concat() method to combine
        // elements from both arrays into a single array
        double[] res
            = Doubles.concat(arr1, arr2, arr3, arr4);

        // Displaying the single combined array
        System.out.println(Arrays.toString(res));
    }
}
Output: 
[1.2, 2.3, 3.4, 4.5, 5.6, 6.4, 7.6, 8.7, 9.7, 0.8]
Reference: https://guava.dev/releases/19.0/api/docs/com/google/common/primitives/Doubles.html#concat(double%5B%5D...)
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