How to pad a String in Java

Given a string str of some specific length, the task is to pad this string with the given character ch, inorder to make the string of length L.

Note: Padding has to be done in all three formats: Left Padding, Right Padding and Center Padding.

Example:

Input: str = “Geeksforgeeks”, ch =’-‘, L = 20
Output:
Left Padding: ————GeeksForGeeks
Center Padding: ——GeeksForGeeks——
Right Padding: GeeksForGeeks————

Input: str = “GfG”, ch =’#’, L = 5
Output:
Left Padding: ##GfG
Center Padding: #GfG#
Right Padding: GfG##

There are many methods to pad a String:

1. Using String format() method: This method is used to return a formatted string using the given locale, specified format string and arguments.

   Note: This method can be used to do only left and right padding.

   Approach:

   • Get the string in which padding is done.
   • Use the String.format() method to pad the string with spaces on left and right, and then replace these spaces with the given character using String.replace() method.
   • For left padding, the syntax to use the String.format() method is:

     String.format("%[L]s", str).replace(' ', ch);
     

   • For right padding, the syntax to use the String.format() method is:

     String.format("%-[L]s", str).replace(' ', ch);
     

   • If the length ‘L’ is less than initial length of the string, then the same string is returned unaltered.

   Below is the implementation of the above approach:

   Example:

   
   

   
   
   

   // Java implementation to pad a String    import java.lang.*; import java.io.*;    public class GFG {        // Function to perform left padding     public static String     leftPadding(String input, char ch, int L)     {            String result             = String                      // First left pad the string                   // with space up to length L                   .format("%" + L + "s", input)                      // Then replace all the spaces                   // with the given character ch                   .replace(' ', ch);            // Return the resultant string         return result;     }        // Function to perform right padding     public static String     rightPadding(String input, char ch, int L)     {            String result             = String                      // First right pad the string                   // with space up to length L                   .format("%" + (-L) + "s", input)                      // Then replace all the spaces                   // with the given character ch                   .replace(' ', ch);            // Return the resultant string         return result;     }        // Driver code     public static void main(String[] args)     {            String str = "GeeksForGeeks";         char ch = '-';         int L = 20;            System.out.println(             leftPadding(str, ch, L));         System.out.println(             rightPadding(str, ch, L));     } }
   Output:

   -------GeeksForGeeks
   GeeksForGeeks-------
   

2. Using Apache Common Lang: Apache Commons Lang package provides the StringUtils class, which contains the leftPad(), center() and rightPad() method to easily left pad, center pad and right pad a String respectively.

   Note: This module has to be installed before running of the code. Hence this code won’t run on Online compilers.

   Approach:

   • Get the string in which padding is done.
   • For left padding, the syntax to use the StringUtils.leftPad() method is:

     StringUtils.leftPad(str, L, ch);
     

   • For center padding, the syntax to use the StringUtils.center() method is:

     StringUtils.center(str, L, ch);
     

   • For right padding, the syntax to use the StringUtils.rightPad() method is:

     StringUtils.rightPad(str, L, ch);
     

   • If the length ‘L’ is less than initial length of the string, then the same string is returned unaltered.

   Below is the implementation of the above approach:

   Example:

   
   

   
   
   

   // Java implementation to pad a String    import java.lang.*; import java.io.*;    public class GFG {        // Function to perform left padding     public static String     leftPadding(String input, char ch, int L)     {            // Left pad the string         String result             = StringUtils.leftPad(str, L, ch);            // Return the resultant string         return result;     }        // Function to perform center padding     public static String     centerPadding(String input, char ch, int L)     {            // Center pad the string         String result             = StringUtils.center(str, L, ch);            // Return the resultant string         return result;     }        // Function to perform right padding     public static String     rightPadding(String input, char ch, int L)     {            // Right pad the string         String result             = StringUtils.rightPad(str, L, ch);            // Return the resultant string         return result;     }        // Driver code     public static void main(String[] args)     {            String str = "GeeksForGeeks";         char ch = '-';         int L = 20;            System.out.println(             leftPadding(str, ch, L));         System.out.println(             centerPadding(str, ch, L));         System.out.println(             rightPadding(str, ch, L));     } }

   Output:

   -------GeeksForGeeks
   ---GeeksForGeeks----
   GeeksForGeeks-------