How to convert a String array to char array in Java

Question

We are given an array of Strings and what we require is a char[], i.e, array of all characters in all the Strings For example:

Input: [i, love, you]

output: [i, l, o, v, e, y, o, u]

First I made an array of arrays.

Then I have found the length of the required char[] array.

I have tried the following so far:

char[][] a1 = new char[str.length][];

for(int i =0;i<str.length;i++){
    a1[i]=str[i].toCharArray();
}

int total=0;
for(int i =0;i<str.length;i++){
    total = total + a1[i].length;
}

char[] allchar = new char[total];

for(int i=0;i<str.length;i++){
    //NOW HERE I WANT TO MERGE ALL THE char[] ARRAYS TOGETHER.
//HOW SHOULD I DO THIS?
}

stop doing brainstorming, and write some code. That would rather help. — Rohit Jain
– Rohit Jain, Commented Oct 25, 2013 at 16:04
Why so rude? A beginner can ask questions on StackOverflow, can't he? Sick of all the downvotes I get! — AmanArora
– AmanArora, Commented Oct 25, 2013 at 16:10
You can ask a question, but you need to show you've made some effort. How can I ... is a bad format for StackOverflow questions. StackOverflow questions should typically be in the following format: This is what I want to accomplish. This is what I've tried. Here is the code that I've actually compiled (or attempted to compile). I'm having this result. I'm expecting this result. What have I done wrong? If you want someone else to write the code to turn an array of Strings into an array of char, then you should hire a programmer. — nhgrif
– nhgrif, Commented Oct 25, 2013 at 16:12

Dan Rothman · Accepted Answer · 2016-07-06 17:14:53Z

8

String[] sArray = {"i", "love", "you"};
    String s = "";
    for (String n:sArray)
        s+= n;
    char[] c = s.toCharArray();

answered Jul 6, 2016 at 17:14

Dan Rothman

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1 Comment

PMARINA Over a year ago

stringbuilder would be more efficient for longer input.

Rahul · Accepted Answer · 2013-10-25 16:37:54Z

2

You can do that like this

char[] allchar = new char[total]; // Your code till here is proper

// Copying the contents of the 2d array to a new 1d array
int counter = 0; // Counter as the index of your allChar array
for (int i = 0; i < a1.length; i++) { 
    for (int j = 0; j < a1[i].length; j++) { // nested for loop - typical 2d array format
        allchar[counter++] = a1[i][j]; // copying it to the new array
    }
}

answered Oct 25, 2013 at 16:37

Rahul

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Comments

Eddie Martinez · Accepted Answer · 2013-10-25 17:33:12Z

1

You can do something like the following method..

    public void converter(String[] stringArray) {


    char[] charsInArray = new char[500];    //set size of char array    
    int counterChars = 0;

    for (int i = 0; i < stringArray.length; i++) { 

        int counterLetters = 0; //declare counter for for amount of letters in each string in the array 

        for (int j = 0; j < stringArray[i].length(); j++) { 


            // below pretty self explanatory extracting individual strings and a
            charsInArray[counterChars] = stringArray[i].charAt(counterLetters);

            counterLetters++;
            counterChars++;
        }
    }


    }

answered Oct 25, 2013 at 17:33

Eddie Martinez

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Comments

Faraz · Accepted Answer · 2016-02-12 06:13:08Z

1

String [] s = new String[]{"i", "love", "you"};

int length = 0;
for (int i = 0; i < s.length; i++) {        
    for (int j = 0; j < s[i].length(); j++) {
        length++;
    }
}

char [] c = new char[length];
int k = 0;
for (int i = 0; i < s.length; i++) {        
    for (int j = 0; j < s[i].length(); j++) {
        c[k] = s[i].charAt(j);
        k++;
    }
}
for (int j = 0; j < c.length; j++) {
    System.out.print("char is: " + c[j]);
}

answered Feb 12, 2016 at 6:13

Faraz

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Comments

Sgshkut · Accepted Answer · 2020-12-08 07:53:21Z

1

In Java 8 we can use streams.

public char[] convert(String[] words) {
    return Arrays.stream(words)
            .collect(Collectors.joining())
            .toCharArray();
}

Here we created a stream from an array using Array.stream(T[] array) where T is the type of the array elements. Than we obtain a string using Collectors.joining(). Finally we get a char array using the String's toCharArray() method.

answered Dec 8, 2020 at 7:53

Sgshkut

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Comments

Gokul Krishna M · Accepted Answer · 2019-01-19 02:40:21Z

0

public static void main(String[] args)
{
    String sentence="Gokul Krishna is class leader";
    String[] array=sentence.split("\\s");
    int counter;
    //String word = new String();
    for(String word:array)
    {
        counter=0;
        char[] wordArray=word.toCharArray();
        for(int i=0;i<wordArray.length;i++)
        {
            counter++;
        }
        System.out.println(word+ " :" +counter);
    }
}

answered Jan 19, 2019 at 2:40

Gokul Krishna M

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1 Comment

chb Over a year ago

"Code only" answers do little to help a novice understand. Please consider explaining your solution.

Kirill · Accepted Answer · 2022-10-10 07:05:55Z

0

public char[] convert(String[] arr) {
    StringBuilder sb = new StringBuilder();
    for (String s : arr) {
        sb.append(s);
    }
    return sb.toString().toCharArray();
}

answered Oct 10, 2022 at 7:05

Kirill

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Comments

Jeremy Caney · Accepted Answer · 2024-09-21 00:26:30Z

-1

String value = "i love java to write";
Stream.of(value.split("")).filter(i -> !i.equals(" ")).forEach(System.out::println);

edited Sep 21, 2024 at 0:26

Jeremy Caney

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answered Sep 19, 2024 at 15:44

Santhosh Kumar

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2 Comments

Jeremy Caney Over a year ago

Why do you prefer this approach over the previous answers? Why should a reader consider this?

cavpollo Over a year ago

Additionally to Jeremy's request for more information I think it is worth pointing out that the expected input is an Array of Strings, which is not the same as a String. So this answer doesn't address the original question.

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