Java Arrays asList() – Examples

Java Arrays asList()

java.util.Arrays.asList() method creates a fixed-size list.

The declaration of asList() method in java.util.Arrays class is

public static <T> List<T> asList(T... a)

From the definition, we can say that

• asList() is a static method.
• Return type of asList() is List. The type of items in the List is same as that of the elements passed as argument to the method.
• asList() does not throw any exception.

If there is any discrepancy with the type of elements, the method can cause a compilation error.

Example 1 – Arrays.asList() with Array as argument

In this example, we will take a string array, and convert it to List using asList() method.

Java Program

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

public class Example {
	public static void main(String[] args) {
		String[] arr = {"apple", "banana", "cherry"};
		List<String> list = Arrays.asList(arr);
		System.out.println(list);
	}
}

Initialize string array arr with three strings. Call Arrays.asList() method with arr passed as argument to it. Since, we have passed a string array, asList() method returns a List<String>.

Output

[apple, banana, cherry]

Example 2 – Arrays.asList() with Elements as Argument

You can also provide multiple elements to asList() method as arguments. The elements has to be separated by comma.

Java Program

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

public class Example {
	public static void main(String[] args) {
		List<String> list = Arrays.asList("apple", "banana", "cherry");
		System.out.println(list);
	}
}

Call Arrays.asList() method and pass the elements as arguments. asList() method returns a List of type backed by the type of elements that we passed to it.

Output

[apple, banana, cherry]

Example 3 – Arrays.asList() with Class Objects

You can also provide elements of user defined class type to asList() method as arguments.

Java Program

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

public class Example {
	public static void main(String[] args) {
		List<Car> list = Arrays.asList(
					new Car("BMW", 25),
					new Car("Toyota", 84),
					new Car("Tata", 19),
					new Car("Hundai", 37)
				);
		System.out.println(list);
	}
}

class Car {
	public String name;
	public int units;
	public Car(String name, int units) {
		this.name = name;
		this.units = units;
	}
	public String toString() {
		return "(" + this.name + "," + this.units + ")";
	}
}

Call Arrays.asList() method and pass the objects as arguments. asList() method returns a List of type backed by the type of elements, which is Car in this example.

Output

[(BMW,25), (Toyota,84), (Tata,19), (Hundai,37)]

Conclusion

In this Java Tutorial, we learned how to use Arrays.asList() method of java.util package, to create a List from objects or an array, with the help of example programs.