How can I pad a String in Java?

Is there some easy way to pad Strings in Java?

Seems like something that should be in some StringUtil-like API, but I can't find anything that does this.

Solution 1:

Since Java 1.5, String.format() can be used to left/right pad a given string.

public static String padRight(String s, int n) {
     return String.format("%-" + n + "s", s);  
}

public static String padLeft(String s, int n) {
    return String.format("%" + n + "s", s);  
}

...

public static void main(String args[]) throws Exception {
 System.out.println(padRight("Howto", 20) + "*");
 System.out.println(padLeft("Howto", 20) + "*");
}

And the output is:

Howto               *
               Howto*

Solution 2:

Padding to 10 characters:

String.format("%10s", "foo").replace(' ', '*');
String.format("%-10s", "bar").replace(' ', '*');
String.format("%10s", "longer than 10 chars").replace(' ', '*');

output:

  *******foo
  bar*******
  longer*than*10*chars

Display '*' for characters of password:

String password = "secret123";
String padded = String.format("%"+password.length()+"s", "").replace(' ', '*');

output has the same length as the password string:

  secret123
  *********

Solution 3:

Apache StringUtils has several methods: leftPad, rightPad, center and repeat.

But please note that — as others have mentioned and demonstrated in this answer — String.format() and the Formatter classes in the JDK are better options. Use them over the commons code.

Solution 4:

In Guava, this is easy:

Strings.padStart("string", 10, ' ');
Strings.padEnd("string", 10, ' ');