Converting ArrayList<String> to int[]

Question

In my code I am converting an ArrayList<String> to int[] by using this code.

ArrayList<String> oneList = new ArrayList<String>();

oneList.add("7");
oneList.add("525");
oneList.add("85");
oneList.add("365");
oneList.add("78");
oneList.add("1");

String[] stringArray = oneList.toArray(new String[oneList.size()]);

int[] arrayOfValues = new int[oneList.size()];  

for(int i = 0;i < stringArray.length;i++)
{   
    try
    {
        arrayOfValues[i] = Integer.parseInt(stringArray[i]);
    }
    catch(Exception e)
    {
        System.out.println("Not an integer value");
    }
}

Is this the most efficient way of completing this or should I be going about it differently? I would also be interested in any alternatives to the way I did it if you have one.

You have to iterate through every elements, and convert each one. Difficult to do better and faster ... — guillaume girod-vitouchkina
– guillaume girod-vitouchkina, Commented Dec 6, 2015 at 21:19
@guillaumegirod-vitouchkina I don't understand what you mean by iterate through every element. Is that what the answer below is doing by Viacheslav Vedenin? — Dan
– Dan, Commented Dec 6, 2015 at 21:21
Yes, your String[] stringArray = oneList.toArray(new String[oneList.size()]); can be avoided, as in the solution given. — guillaume girod-vitouchkina
– guillaume girod-vitouchkina, Commented Dec 6, 2015 at 21:25

Dan · Accepted Answer · 2015-12-06 21:44:21Z

4

Better use following code:

ArrayList<String> oneList = new ArrayList<String>();

oneList.add("7");
oneList.add("525");
oneList.add("85");
oneList.add("365");
oneList.add("78");
oneList.add("1");

int[] arrayOfValues = new int[oneList.size()];  
int i = 0;
for(String value: oneList)
{   
    try
    {
        arrayOfValues[i] = Integer.parseInt(value);
        i++;
    }
    catch(Exception e)
    {
        System.out.println("Not an integer value");
    }
}

In your code:

1) You create a String[] array but that not need at all.

2) Using a for each loop is better than for(int i..)

3) If you have exception, arrayOfValues has empty element, for example if oneList = {"1", "aaa", "2"} then arrayOfValues = {1, 0, 2}. However it is sometimes better if arrayOfValues = {1, 2}

edited Dec 6, 2015 at 21:44

Dan

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answered Dec 6, 2015 at 21:21

Slava Vedenin

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4 Comments

OneCricketeer Over a year ago

Why is a for each loop better?

Slava Vedenin Over a year ago

It's more readable in the most case, so other programmers can understand your code quite easy

OneCricketeer Over a year ago

I just don't see the need when you replace it with a for (int i ..., then do String value = oneList.get(i) on the first line. While it is more readable, it is not as concise when you have to remember to manually assign and increment i in 2 different lines.

AlexR Over a year ago

Don't catch "Exception". Catch NumberFormatException instead, you don't want to catch everything that could possibly go wrong.

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