Java: String - add character n-times [duplicate]

Question

This question already has answers here:

Simple way to repeat a String in java (30 answers)

Closed 2 years ago.

Is there a simple way to add a character or another String n-times to an existing String? I couldn’t find anything in String, Stringbuilder, etc.

Answer 1

In addition to the answers above, you should initialize the StringBuilder with an appropriate capacity, especially that you already know it. For example:

int capacity = existingString.length() + n * appendableString.length();
StringBuilder builder = new StringBuilder(capacity);

Answer 2

In case of Java 8 you can do:

int n = 4;
String existing = "...";
String result = existing + String.join("", Collections.nCopies(n, "*"));

Output:

...****

In Java 8 the String.join method was added. But Collections.nCopies is even in Java 5.

Answer 3

For the case of repeating a single character (not a String), you could use Arrays.fill:

  String original = "original ";
  char c = 'c';
  int number = 9;

  char[] repeat = new char[number];
  Arrays.fill(repeat, c);
  original += new String(repeat);