Splitting a string into sub-strings of equal length

Question

I'm taking an intro prog class so I am only allowed to use methods of string objects. There is probably other 'prettier' way to solve it but I'm not allowed to use more advanced techniques. Pretend that I have a string "abcdefghijklmnopqrstuvwxyz" I want to split it into different parts of equal length. My attempted solution is below which does not work. It only prints out one part, in this case, "aaa." I'm not sure which string method is the best. I figured substring which be the way to go but not sure on how to implement it correctly.

 int splitSize = 5
 String s = "aaabbbcccdddeeefffggghhhiiijjjkkklllmmmnnnooo";
 for (int i = 0; i < s.length() / splitSize; i++) {
    s = s.substring(i, i + 3);
 }

Answer 1

Let us assume you want your output as an array of strings (you are currently ignoring output; another option would be to print it). Then you can implement something like

public static String[] split(String s, int splitSize) {
    String[] result = new String[(s.length()+splitSize-1)/splitSize];
    for (int i=0, j=0; i<s.length(); i+=splitSize) {
        result[j++] = s.substring(i, Math.min(s.length(), i+splitSize));
    }
    return result;
}

This will return an array with consecutive substrings of splitSize characters each, where the last one may be smaller than the rest if it could not be filled in. If you need to even them out, there's something called Bresenham 's algorithm that does just that (although it is more commonly used for drawing lines)

Notice that "1".substring(0,3) throws an exception - you should not try to take a larger substring than is available.

You can avoid using Math.min when adding to the result by either using an if statement or the ternary operator ( ?: ).

Answer 2

Try this ( s.length() must be a multiple of splitSize ).

int splitSize = 5;
String s = "aaabbbcccdddeeefffggghhhiiijjjkkklllmmmnnnooo";
for (int i = 0; i < s.length();) {
    System.out.println(s.substring(i, i + splitSize));
    i = i + splitSize;
}

Answer 3

You should use "count/flag" to keep an eye on string index and split size. check out this code

int splitSize = 5
String s = "aaabbbcccdddeeefffggghhhiiijjjkkklllmmmnnnooo";
int count = 0;
String tempString = "";
for (int i = 0; i < s.length(); i++) {
    String str_atIndex = Character.toString(s.charAt(i));
    if(count < splitSize){
        tempString = tempString + str_atIndex;
        count++;
    }else{
        count = 0;
        System.out.print(tempString);
        tempString = "";
    }
}

Answer 4

In your for loop, you are trying to divide String(s) by an integer(splitSize). It will give you a compile error.

You can try something like this:

static void split(int splitSize) {
        String s = "aaaaabbbbbccccc";

        for (int i = 0; i < s.length(); i += splitSize) {
            System.out.println(s.substring(i, i+splitSize));
        }
     }

Prints:

aaaaa
bbbbb
ccccc

If that's what you are looking for. Hope that helps.

Answer 5

Another way is to use String's charAt method.

int splitSize = 5;
String s = "aaabbbcccdddeeefffggghhhiiijjjkkklllmmmnnnooo";

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

    System.out.print(s.charAt(i));

    if ((i + 1) % splitSize == 0) {
        System.out.print("\n");
    }
}

Each character in the string is printed to the console and when the index i is divisible with the splitSize , it starts a new line.