Generate fixed length Strings filled with whitespaces

Since Java 1.5 we can use the method java.lang.String.format(String, Object...) and use printf like format.

The format string "%1$15s" do the job. Where 1$ indicates the argument index, s indicates that the argument is a String and 15 represents the minimal width of the String. Putting it all together: "%1$15s".

For a general method we have:

public static String fixedLengthString(String string, int length) {
    return String.format("%1$"+length+ "s", string);
}

Maybe someone can suggest another format string to fill the empty spaces with an specific character?

Utilize String.format's padding with spaces and replace them with the desired char.

String toPad = "Apple";
String padded = String.format("%8s", toPad).replace(' ', '0');
System.out.println(padded);

Prints 000Apple.

Update more performant version (since it does not rely on String.format), that has no problem with spaces (thx to Rafael Borja for the hint).

int width = 10;
char fill = '0';

String toPad = "New York";
String padded = new String(new char[width - toPad.length()]).replace('\0', fill) + toPad;
System.out.println(padded);

Prints 00New York.

But a check needs to be added to prevent the attempt of creating a char array with negative length.

This code will have exactly the given amount of characters; filled with spaces or truncated on the right side:

private String leftpad(String text, int length) {
    return String.format("%" + length + "." + length + "s", text);
}

private String rightpad(String text, int length) {
    return String.format("%-" + length + "." + length + "s", text);
}