How do I enter parameters for an ArrayList in BlueJ?
arraylist, bluej, java
Solution
You need to create an instance of `ArrayList` to pass to your method when you call it. With your project open in the main BlueJ window, click on the Tools menu, then on "Use Library Class...", then select `java.util.ArrayList` from the Class menu. Also select the no-argument constructor from the list that appears, then click Ok.
BlueJ will then display another dialog asking you for a name for the instance and for a type parameter for the `ArrayList`. Enter a name and `Integer` for the type parameter.
After you click Ok, the new `ArrayList` instance will appear in the object bench area at the bottom of the main BlueJ window.
When you right click on the new instance, BlueJ will display a menu of methods that can be called on it. Select the `boolean add(Integer)` method a few times to add some values to the instance.
Finally, when you right click on your test class and call the `toArray` method, you can enter the name of the `ArrayList` instance to pass it as the argument to your method.
The results of the method call are displayed in a dialog.
Click the Inspect button to view the contents of the `int` array returned from your method, or click the Get button to add it to the object bench.
Problem
In BlueJ, if I write a method that takes an array as a parameter, then when I want to test that method with a method call I have to enter the elements with curly braces, so: {1,2,3} How do I do a method call for an `ArrayList`? Here is my code: ``` import java.util.*; public class Test2{ public static int[] toArray(ArrayList<Integer>a){ int len = a.size(); int []b = new int[len]; for(int i = 0; i<len; i++){ b[i] = a.get(i); } return b; } } ``` Now I want to test it in BlueJ, what should I type in the following dialog box?