adding values on array java

Question

i don't know what's wrong. the array should be in Number or int.

here's my code:

Number[] freq;

    int place = 0;

    BufferedReader br = new BufferedReader(new FileReader(new File("this.txt")));

    String read;

    String[] temp;

    int num;

    while((read = br.readLine())!=null)
    {
        temp = read.split(",");
        for(int i = 0; i<=temp.length; i++)
        {
            String t = temp[i];
            num = Integer.parseInt(t);
            freq[place] = num;
            place++;
        }

    }

    System.out.println("done");

it shouldn't output some heavy result but i need it working. i always get the error

variable freq might not have been initialized.
freq[place] = num;

Java arrays are not dynamic, you need to actually initialize them to a length of some sort before you use them. — Erik
– Erik, Commented Dec 3, 2014 at 10:48
the values that are going to be in that array aren't always in the same size. i know arrays must be first initialized with size but in this program it must be depended on how many are in the text file — dimmed
– dimmed, Commented Dec 3, 2014 at 10:52
Then you need to use another type of variable, such as an ArrayList, which can be dynamic in size. — Erik
– Erik, Commented Dec 3, 2014 at 10:53
(better to update your question if you have new information) dynamic sizing is a fairly common requirement, and there are usually better data structures than arrays. Have a look at Lists for examples — Jan Groth
– Jan Groth, Commented Dec 3, 2014 at 10:56
sorry about that. i was searching about that then can't find answer like mine, decided to post the a question. i didn't notice at first that that make the title of this. btw, thanks everyone who answered! — dimmed
– dimmed, Commented Dec 3, 2014 at 11:07

Jan Groth · Accepted Answer · 2014-12-03 10:49:05Z

3

You must initialise the array.

Number[] freq = new Number[someSize]

answered Dec 3, 2014 at 10:49

Jan Groth

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Comments

Erik · Accepted Answer · 2014-12-03 10:58:01Z

2

You need to set a size for the Array. Since you indicated in the comments that it has to be dynamic, you'll have to instead use a different kind of variable that can be used with dynamic length, such as an ArrayList.

See this example:

// initialize an ArrayList:
List<Number> freq = new ArrayList<Number>();
BufferedReader br = new BufferedReader(new FileReader(new File("this.txt")));

String read;
String[] temp;

int num;

while((read = br.readLine())!=null)
{
    temp = read.split(",");
    for(int i = 0; i<=temp.length; i++)
    {
        String t = temp[i];
        num = Integer.parseInt(t);
        freq.add( num );
    }

}

System.out.println("done");

answered Dec 3, 2014 at 10:58

Erik

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1 Comment

dimmed Over a year ago

nice it worked! thanks! now i know that List can be like that.

Harry · Accepted Answer · 2014-12-03 10:49:26Z

0

You need to set an array size before you use an array in JAVA.

int[] someArray= new int[size]

answered Dec 3, 2014 at 10:49

Harry

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1 Comment

Tom Over a year ago

There is no Int available in Java. You meant int[size]?

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