1. Overview
In this article, we will learn to convert varargs to List or Array in Java. Varargs introduced in Java 5 and provide a short-hand for methods that support a variable number of parameters of one type.
2. Java convert varargs to Array
The varargs takes an arbitrary number of values (zero or multiple values as a method parameter). It creates an array automatically and puts the values into the array prior to invoking the method. You must pass multiple arguments in an array or a sequence of arguments, but the varargs feature automates and hides the process.
You can consider the varargs as a simplification of an array.
In the example, the below main method passes a variable number of text values "a", "b", "c" (a sequence of arguments) to the foo method. The args variable argument is assigned directly to String array strArray.
public static void main(String[] args){
foo("a", "b", "c");
}
private static void foo(String...args) {
String[] strArray = args;
for (int i = 0; i < strArray.length; i++) {
System.out.print(strArray[i]);
}
}
/* prints
abc */
As mentioned earlier, you can also pass the multiple arguments in an array. For example, the main method passes the strArray as a variable argument to the foo method.
public static void main(String[] args){
String[] strArray = {"a", "b", "c"};
foo(strArray);
}
private static void foo(String...args) {
String[] strArray = args;
for (int i = 0; i < strArray.length; i++) {
System.out.print(strArray[i]);
}
}
3. Java convert varargs to List
To convert the variable argument to a list, you can use Arrays.asList() method. This method is used to return a fixed-size list backed by the specified array. Since varargs is a simplified form of an array, you can apply the operations that you can perform on an Array to varargs as well.
public static void main(String[] args){
foo("a", "b", "c");
}
private static void foo(Object...args) {
System.out.println("foo called, args: " + Arrays.asList(args));
}
/* prints
foo called, args: [a, b, c] */
Alternatively, you can also use Collections.addAll method to convert a varargs to list.
List<String> list = new ArrayList<>(); Collections.addAll(list, args);
4. Conclusion
To sum up, we have learned to convert varargs to List or Array in Java along with examples.
