How to add padding to a String in Java

This post will discuss how to add padding to a String in Java.

1. Using `String.format()` method

A common solution to left/right pad a string with spaces is using the String.format() method. For example,

public class Main

{

public static String padLeft(String s, int n) {

return String.format("%" + n + "s", s);

}

public static String padRight(String s, int n) {

return String.format("%-" + n + "s", s);

}

public static void main(String[] args)

{

String s = "ABC";

int n = 5;

System.out.println(padLeft(s, n)); // " ABC"

System.out.println(padRight(s, n)); // "ABC "

}

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If your string is numeric, you can pad it with zeros by converting it to an integer:

public class Main

{

public static String padLeft(String s, int n) {

return String.format("%0" + n + "d", Integer.parseInt(s));

}

public static void main(String[] args)

{

String s = "123";

int n = 5;

System.out.println(padLeft(s, n)); // 00123

}

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2. Using Apache Commons `StringUtils` class

Alternatively, you can leverage Apache Commons Lang’s StringUtils class leftPad() and rightPad() utility methods, which can add specified padding to the start and end of a string, respectively.

import org.apache.commons.lang3.StringUtils;

public class Main

{

public static void main(String[] args)

{

String str = "ABC";

int size = 5;

char padChar = '0';

System.out.println(StringUtils.leftPad(str, size, padChar)); // 00ABC

System.out.println(StringUtils.rightPad(str, size, padChar)); // ABC00

}

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3. Using Guava

You can also leverage padStart() and padEnd() method offered by Guava’s Strings class. The method signature remains the same as the above solution.

import com.google.common.base.Strings;

public class Main

{

public static void main(String[] args)

{

String str = "ABC";

int size = 5;

char padChar = '0';

System.out.println(Strings.padStart(str, size, padChar)); // 00ABC

System.out.println(Strings.padEnd(str, size, padChar)); // ABC00

}

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That’s all about padding a String in Java.

How to add padding to a String in Java

1. Using String.format() method

2. Using Apache Commons StringUtils class

3. Using Guava

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1. Using `String.format()` method

2. Using Apache Commons `StringUtils` class