Problem:
In Java there is a couple of ways to add an array of items to a collection. In the following examples we’ll cover a few of them.
Solution:
When programming in Java, very often there’s a need to add some elements to a collection. It can be done in different ways as you can see in the following example:
package com.farenda.java;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class CollectionsAddAll {
public static void main(String[] args) {
List<String> items = new ArrayList<>();
// Too verbose:
items.add("added");
items.add("manually");
System.out.println(items);
// Sometimes better:
items.addAll(Arrays.asList("as", "an", "array"));
System.out.println(items);
// The best way: reuse!
Collections.addAll(items, "reusing", "Collections", "library");
System.out.println(items);
}
}
Many people don’t even know that there’s a method java.util.Collections.addAll(Collection, T… items) to add an array (so varargs too) of elements to a Collection. In most cases the method is better than Arrays.asList version.
Remember Item 47: Know and use the libraries from excellent “Effective Java, 2nd Edition” book! It will return many times! :-)
