It can be an obvious question but I am thinking how to replace the method below with java 8 streams.
private String assembleString(int numberOfCharacters, char character) { StringBuilder stringBuilder = new StringBuilder(); for (int i = 0; i < numberOfCharacters; i++) { stringBuilder.append(character); } return stringBuilder.toString(); } I am new in Java, so java 8 it is like an unexplored world for me.
Thank you!
All you need is just Collections.nCopies
private static String assembleString(int numberOfCharacters, char character) { return String.join("", Collections.nCopies(numberOfCharacters, String.valueOf(character)) ); } You can use Stream.generate:
return Stream.generate(() -> String.valueOf(character)) .limit(numberOfCharacters) .collect(Collectors.joining()); or IntStream.rangeClosed:
return IntStream.rangeClosed(1, numberOfCharacters) .mapToObj(n -> String.valueOf(character)) .collect(Collectors.joining()); This should suffice.
IntStream.range(0, numberOfCharacters) .mapToObj(value -> character) .forEach(stringBuilder::append); EDIT:
Taking Holger's suggestion, this would be even more functional and cleaner.
IntStream.range(0, numberOfCharacters) .map(value -> character) .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append); 
.map(value -> character) .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append) instead of .mapToObj(value -> character) .forEach(stringBuilder::append) to an existing StringBuilder. It would also avoid boxing into Character objects.
forEachOrdered ?
Use IntStream:
private String assembleString(int numberOfCharacters, char character) { return IntStream.range(0, numberOfCharacters) .mapToObj(i -> String.valueOf(character)).collect(Collectors.joining()); } 
With Java 11+, you could also use String::repeat:
return String.repeat(Character.toString(character), numberOfCharacters); Or you could "steal" their implementation:
char[] repeated = new char[numberOfCharacters]; Arrays.fill(repeated, character); return new String(repeated); 
Arrays.fill(…) also was the first thing that came into my mind. Of course, an implementation within String itself, like repeat avoids the defensive copying of the array.Just for "completeness", without apparent loops or Streams:
private String assembleString(int numberOfCharacters, char character) { return new String(new char[numberOfCharacters]).replace('\0', character); } How: Creates a new char array of size 'numberOfCharacters', which will be initialised with 'null' characters. Construct a String from this array, then replace all occurrences of the null character with the desired one.
