Convert char array to multiple strings
I need to convert a char array to multiple strings of a specific size. For example, given this array:
char[] bases = new char[]{'a', 'c', 'c', 't', 'a', 'c', 'a', 't', 'a', 'c', 'c', 't', 'a', 'c', 'a', 't'};
the expected result will be 5 :
accta
catac
ctaca
I am currently using this code:
int ls = 5;
String str = "";
for (int i = 1; i < bases.length; i++) {
str += bases[i - 1];
if (i%ls == 0) {
str += '\n';
}
}
Is there a built-in function to achieve this in java 8? Is there a better way to solve this problem?
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You can convert string char[]
to string then you can use split with some regex like:
String s = String.valueOf(bases);//result = acctacatacctacat
System.out.println(Arrays.toString(s.split("(?<=\\G.{5})")));
If you want to do it in one line:
String[] spl = String.valueOf(bases).split("(?<=\\G.{5})");
Output
[accta, catac, ctaca, t]
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You should almost never use string concatenation in a loop to construct a string.
Use StringBuilder
:
StringBuilder sb = new StringBuilder(bases.length + (4 + bases.length) / 5);
for (int i = 0; i < bases.length; i += 5) {
sb.append(bases, i, Math.min(5, bases.length - i));
sb.append("\n");
}
String str = sb.toString();
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Since in this case you have a very clear idea of the sequence you need to create, it may be most efficient to use your own code to create the appropriate one char[]
:
final int ls = 5;
final char[] result = new char[bases.length + (bases.length + ls - 1) / ls]
int nextIndex = 0;
for (int i = 0; i < bases.length; i += ls) {
final int size = bases.length - i >= ls ? ls : bases.length - i;
System.arraycopy(bases, i, result, nextIndex, size);
nextIndex += size;
result[nextIndex++] = '\n';
}
final String resultAsString = new String(result);
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This could be a different solution to your question using the power of java8 stream: (for understanding, I'll leave the answer step by step, but a lot can be condensed and simplified / collected later)
int charsPerChunk = 5;
char[] myCharArray = { 'H', 'e', 'l', 'l', 'o', '+', 'X', 'o', 'c', 'e', '!' };
// turn the char array into a Stream of Characters
Stream<Character> myStreamOfCharacters = IntStream.range(0, myCharArray.length).mapToObj(i -> myCharArray[i]);
// collect that into a list of characters
List<Character> myListOfCharacters = myStreamOfCharacters.collect(Collectors.toList());
int size = myListOfCharacters.size();
int fullChunks = (size - 1) / charsPerChunk;
// get a stream of list of characters
Stream<List<Character>> result = IntStream
.range(0, fullChunks + 1)
.mapToObj( x -> myListOfCharacters.subList(x * charsPerChunk, x == fullChunks ? size : (x + 1) * charsPerChunk));
// print it
result.forEach(System.out::println);
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