How to use valueOf to convert a string array to a int array?

Question

I want to convert following list into a int array. I have tried to use valueof but I don't know how to use it. I don't want to parse it.

I have a string array here: String[] arr1 = new String[]{"5","5","15","5","10","10", "5", "10", "20", "15"};

Here is the code I tried:

int num = Integer.valueOf(arr1);

I am getting a error message:

error: no suitable method found for valueOf(String[])
    int num = Integer.valueOf(arr1);
                     ^
    method Integer.valueOf(String) is not applicable
      (argument mismatch; String[] cannot be converted to String)
    method Integer.valueOf(int) is not applicable
      (argument mismatch; String[] cannot be converted to int)
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error

If you want to convert those string representations of numbers to ints, then you do want to parse them. — khelwood
– khelwood, Commented Nov 24, 2019 at 3:37
Thank you for your answer.I know parsing is probably easier but I am told to not use it. — TheGamer27
– TheGamer27, Commented Nov 24, 2019 at 3:39
Thank you for the clarification, I am new to programming so I was confused. — TheGamer27
– TheGamer27, Commented Nov 24, 2019 at 3:43
Possible duplicate of Converting a String array into an int Array in java — Ankit Sharma
– Ankit Sharma, Commented Nov 24, 2019 at 4:36

Elliott Frisch · Accepted Answer · 2019-11-24 03:33:02Z

2

I assume you want to map every value in the arr1 array to an int, and the result should be an int[] (not one int). Stream the array, map the elements to an int, and then invoke toArray. Like,

int[] numArr = Arrays.stream(arr1).mapToInt(Integer::valueOf).toArray();

Note that invoking valueOf in this way is still an example of parsing the String to an int.

answered Nov 24, 2019 at 3:33

Elliott Frisch

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2 Comments

TheGamer27 Over a year ago

How would I use valueOf?

TheGamer27 Over a year ago

Thank you for the clarification, I am new to programming so I was confused.

boot-and-bonnet · Accepted Answer · 2019-11-24 03:32:36Z

1

Using Streams:

int[] intArray = Stream.of(arr1).mapToInt(Integer::parseInt).toArray();

answered Nov 24, 2019 at 3:32

boot-and-bonnet

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3 Comments

TheGamer27 Over a year ago

Thank you for your answer, as mentioned I do not want to parse at all. Is there any other way to do it.

boot-and-bonnet Over a year ago

valueOf calls parseInt internally so not sure you have a choice

TheGamer27 Over a year ago

Thank you for the clarification, I am new to programming so I was confused.

Vikalp Patel · Accepted Answer · 2019-11-24 03:39:10Z

1

You can iterate through each element of Array and convert it into Int and push it into IntArray.

String[] arr1 = new String[]{"5","5","15","5","10","10", "5", "10", "20", "15"};
int[] intArr = new int[arr1.length];

for (int i = 0; i < arr1.length; i++) {
  intArr[i] = Integer.valueOf(arr1[i]);
}

valueOf internally uses parseInt

public static Integer valueOf(String s) throws NumberFormatException {
    return Integer.valueOf(parseInt(s, 10));
}

edited Nov 24, 2019 at 3:39

answered Nov 24, 2019 at 3:34

Vikalp Patel

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3 Comments

TheGamer27 Over a year ago

Thank you for your answer, as mentioned I do not want to parse at all. Is there any way I can do it using valueOf?

Vikalp Patel Over a year ago

Yes, you can use valueOf instead of parseInt. valueOf returns an int and not the int arr. That's why you need to push it into int arr either using for each or Stream as other answers has suggested.

TheGamer27 Over a year ago

Thank you for the clarification, I am new to programming so I was confused.

WJS · Accepted Answer · 2019-11-24 04:04:04Z

1

Here is how you can do it without using valueOf or parseInt.

      String[] arr1 = new String[] { "5", "5", "15", "5", "10", "10", "5", "10"
      };


      int[] vals = Arrays.stream(arr1).mapToInt(str -> str.chars().reduce(0,
            (val, ch) -> val * 10 + (ch - '0'))).toArray();

      System.out.println(Arrays.toString(vals));

Here are its limitations:

If your strings contain characters other than digits. It will quietly give you the wrong answer.
It does not handle negative values.
It will throw an exception if any of the individual numbers exceed Integer.MAX_VALUE.

My recommendation would be to use Integer.valueOf. That is what it's for.

edited Nov 24, 2019 at 4:04

answered Nov 24, 2019 at 3:51

WJS

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