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I would like to know how to create a method which takes an ArrayList of Integers (ArrayList) as a parameter and then display the contents of the ArrayList?

I have some code which generates some random numbers and populates the ArrayList with the results, however I keep having errors flag up in eclipse when attempting to create this particular method.

Here is what I have so far:

public void showArray(ArrayList<Integer> array){

    return;

}

I know that it is very basic, but I am unsure exactly how to approach it - could it be something like the following?

public void showArray(ArrayList<Integer> array){

    Arrays.toString(array);

}

Any assistance would be greatly appreciated.

Thank you.

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4 Answers

up vote 1 down vote accepted

I'm assuming this is a learning exercise. I'll give you a few hints:

  • Your method is named showArray, but an ArrayList<T> is of type List<T>, and is not an array. More specifically it is a list that is implemented by internally using an array. Either change the parameter to be an array or else fix the name of the method.
  • Use an interface if possible instead of passing a concrete class to make your method more reusable.
  • Minor point: It may be better to have your method return a String, and display the result outside the method.

Try something like this:

public void printList(List<Integer> array) {
    String toPrint = ...;
    System.out.println(toPrint);
}

You can use a loop and a StringBuilder to construct the toPrint string.

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Good points about the method/parameter name and the use of List over ArrayList, but he asks for a function to "display the contents", not return the contents as a String. – Matthew Gilliard Mar 4 '11 at 22:39
up vote 1 down vote

Is there any reason why System.out.println( array ); wouldn't work for you?

Output will be like:

[1, 2, 3]
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I initially tried this, and even though it compiled correctly, I was unable to get the main method to invoke/call showArray...could somebody please tell me how to have the main method call showArray? I have tried every possibility that I could think of but sadly, to no avail. Thank you. – SnookerFan Mar 4 '11 at 23:27
Thank you, mjg123. I took a look at the website but unfortunately nothing on there worked for me. Do you (or anybody else) have another suggestion that I could attempt? Thanks again. – SnookerFan Mar 5 '11 at 0:05
up vote 0 down vote

If you are looking to print the array items, try

public void showArray(ArrayList<Integer> array){

 for(int arrayItem : array)
 {
    System.out.println(arrayItem);
 }

}
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up vote -1 down vote

This sounds like someone wants us to do their homework. You don't have to return anything if you are just displaying it, and if the method has a void return type. I don't know exactly what you want but is it something along the lines of System.out.println(array.elementAt(index))? then you would need a loop.

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