Given a String how to convert it to an Array: Java

Question

so I'm pretty new at Java and StackOverflow (That's what they all say) and I am stuck at the given problem:

My method is given a String e.g.: "[ 25 , 25 , 125 , 125]". Now the method should return an Array of integers representation of the String provided, that is: it should return [25,25,125,125].

Here is a segment of my method. Note: input is the String provided

if(input.charAt(index) == '['){
    index++;
    int start = index;

    while(index <= input.length() && input.charAt(index) != ']'){
        index++;
    }

    String[] arrayStr = input.substring(start, index).split(",");
    int[] arrayInt = new int[4];
    for (int i = 0; i < arrayStr.length; i++){
        arrayInt[i] = Integer.parseInt(arrayStr[i]);
    }
    return arrayInt;

My code works if input is: "[25,25,125,125]" (If there are no spaces between the numbers). However if there are spaces between the numbers then my code doesn't work and I understand why, but I am struggling to find a way to solve this problem. Any help will be appreciated.

Read the javadoc of String. It has methods like trim(), indexOf() and lastIndexOf() that you should use. And don't assume your array has 4 elements. Use arrayStr.length. — JB Nizet
– JB Nizet, Commented Apr 12, 2015 at 16:09
Can your string contain only [numbers] or can it also be in form some words [numbers, xxx] other words? — Pshemo
– Pshemo, Commented Apr 12, 2015 at 16:09
Why not simply remove all spaces, before processing? String s = input.replaceAll("\\s", ""); — Nicholas Betsworth
– Nicholas Betsworth, Commented Apr 12, 2015 at 16:11
@Pshemo Yes the string can only be [numbers], if there are any words within the square brackets I'll have to return an exception. — HPSS
– HPSS, Commented Apr 12, 2015 at 22:57

giorashc · Accepted Answer · 2015-04-12 16:10:40Z

3

Spaces will fail with Integer.parseInt(arrayStr[i]) (e.g. the string "25 " is not a valid number as it contains a space. (parseInt will throw an exception in such cases.)

However you can solve it quickly by trimming your array elements:

Integer.parseInt(arrayStr[i].trim())

trim() returns a copy of the string without leading/trailing white space

answered Apr 12, 2015 at 16:10

giorashc

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singhakash · Accepted Answer · 2015-04-12 16:12:17Z

2

You can replace the space with empty in the string

input=input.replace(" ","")

answered Apr 12, 2015 at 16:12

singhakash

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Pshemo · Accepted Answer · 2015-04-12 23:11:55Z

2

You can

remove [ and ] and all spaces
split on , to get all tokens
iterate over all tokens
- parse string number to int
- add parsed int to result array

So your code can look like

String data = "[ 25 , 25 , 125 , 125]";
String[] tokens = data.replaceAll("\\[|\\]|\\s", "").split(",");
int[] array = new int[tokens.length];
for (int i=0; i<tokens.length; i++){
    array[i]=Integer.parseInt(tokens[i]);
}

Or if you have Java 8 you can use streams like

int[] array = Stream.of(data.replaceAll("\\[|\\]|\\s", "").split(","))
        .mapToInt(number -> Integer.parseInt(number))
        .toArray();

answered Apr 12, 2015 at 23:11

Pshemo

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