Java – Right pad a string with spaces or zeros

Java programs to add right padding to a string in such a way that total string length should be a fixed predefined number.

For example, if we have a string of length 10, and we want to increase it’s length to 15 – by adding right padding then use the example given this post.

1. How right padding is added

When you add right padding, you essentially add a character repeatedly to the end of string – until string length reaches to defined length.

For example –		//no padding    		//right padding of 4 spaces		//right padding of 4 dots
howtodoinjava.com0000		//right padding of 4 zeros

Read More: Java remove trailing whitespaces from String

2. Java right padding with spaces

To add right padding, most useful and easy way is to use StringUtils.rightPad() method.

2.1. Maven dependency


2.2. Method Syntax (overloaded)

 * @param str  		- the String to pad out, may be null
 * @param size 		- the size to pad to i.e. Total length of result string
 * @param padChar  	- the character or string to pad with
 * @return right padded String or original String if no padding is necessary or if null String input

public static String rightPad(final String str, final int size) {...}
public static String rightPad(final String str, final int size, String padStr) {...}
public static String rightPad(final String str, final int size, final char padChar) { ... }

2.3. Right padding example

//Added # character to verify padded blank spaces

System.out.println( StringUtils.rightPad("howtodoinjava", 20, " ") + "#");
System.out.println( StringUtils.rightPad("howtodoinjava", 30, " ") + "#");
System.out.println( StringUtils.rightPad("howtodoinjava", 15, " ") + "#");

Program output:

howtodoinjava       #
howtodoinjava                 #
howtodoinjava  #

3. Java right pad a string with zeros

Java program to use StringUtils.rightPad() method to right pad a string with zeros, by adding trailing zeros to string.

System.out.println( StringUtils.rightPad("0123456789", 10, "0") );
System.out.println( StringUtils.rightPad("0123", 10, "0") );
System.out.println( StringUtils.rightPad("012345", 10, "0") );

Program output:


4. Summary

In above examples, we learned to right pad string with spaces to fixed length. We also saw to right pad a number with zeros.

Use this right padding to format strings to fixed length – to display in UI.

Happy Learning !!


StringUtils Java Doc

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