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

Answer 1

for(int i = 0; i < n; i++) {
    existing_string += 'c';
}

but you should use StringBuilder instead, and save memory

int n = 3;
String existing_string = "string";
StringBuilder builder = new StringBuilder(existing_string);
for (int i = 0; i < n; i++) {
    builder.append(" append ");
}

System.out.println(builder.toString());

Answer 2

You can use Guava's Strings.repeat method:

String existingString = ...
existingString += Strings.repeat("foo", n);

Answer 3

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 4

Keep in mind that if the "n" is large, it might not be such a great idea to use +=, since every time you add another String through +=, the JVM will create a brand new object (plenty of info on this around).

Something like:

StringBuilder b = new StringBuilder(existing_string);
for(int i = 0; i<n; i++){
    b.append("other_string");
}
return b.toString();

Not actually coding this in an IDE, so minor flaws may occur, but this is the basic idea.

Answer 5

How I did it:

final int numberOfSpaces = 22;
final char[] spaceArray = new char[numberOfSpaces];
Arrays.fill(spaces, ' ');

Now add it to your StringBuilder

stringBuilder.append(spaceArray);

or String

final String spaces = String.valueOf(spaceArray);

Answer 6

Its better to use StringBuilder instead of String because String is an immutable class and it cannot be modified once created: in String each concatenation results in creating a new instance of the String class with the modified string.