String class doesn’t have any method that directly sort a string, but we can sort a string by applying other methods one after other.
Method 1(natural sorting) :
- Apply toCharArray() method on input string to create a char array for input string.
- Use Arrays.sort(char c[]) method to sort char array.
- Use String class constructor to create a sorted string from char array.
Note : As we know that String is immutable in java, hence in third step we have to create a new string.
Sort a String alphabetically :
Examples :
Input string : "geeksforgeeks" Output string : "eeeefggkkorss"
// Java program to sort a string alphabetically import java.util.Arrays; public class GFG { // Method to sort a string alphabetically public static String sortString(String inputString) { // convert input string to char array char tempArray[] = inputString.toCharArray(); // sort tempArray Arrays.sort(tempArray); // return new sorted string return new String(tempArray); } // Driver method public static void main(String[] args) { String inputString = "geeksforgeeks"; String outputString = sortString(inputString); System.out.println("Input String : " + inputString); System.out.println("Output String : " + outputString); } } |
Output:
Input String : geeksforgeeks Output String : eeeefggkkorss
Arrays.sort(char c[]) method sort characters based on their ASCII value, we can define our custom Comparator to sort a string.
Method 2(custom sorting):
- Convert input string to Character array. There is no direct method to do it. We will use for loop to fill the array.
- Use Arrays.sort(T [ ], Comparator c) method to sort Character array. For this, we must have to implement compare() method based on our custom sorting behavior.
- Now we can use StringBuilder to convert Character array to String.
Sort a mixed string(containing uppercase and lowercase characters) :
Examples :
Input String : GeeksforGeeks Output String : eeeefGGkkorss
// Java program to sort a mixed string import java.util.Arrays; import java.util.Comparator; public class GFG { // Method to sort a mixed string public static String sortString(String inputString) { // convert input string to Character array Character tempArray[] = new Character[inputString.length()]; for (int i = 0; i < inputString.length(); i++) { tempArray[i] = inputString.charAt(i); } // Sort, ignoring case during sorting Arrays.sort(tempArray, new Comparator<Character>(){ @Override public int compare(Character c1, Character c2) { // ignoring case return Character.compare(Character.toLowerCase(c1), Character.toLowerCase(c2)); } }); // using StringBuilder to convert Character array to String StringBuilder sb = new StringBuilder(tempArray.length); for (Character c : tempArray) sb.append(c.charValue()); return sb.toString(); } // Driver method public static void main(String[] args) { String inputString = "GeeksforGeeks"; String outputString = sortString(inputString); System.out.println("Input String : " + inputString); System.out.println("Output String : " + outputString); } } |
Output:
Input String : GeeksforGeeks Output String : eeeefGGkkorss
Note :
public int compare(Object o1, Object o2)
{
// have to return -ve if o1 has to come before o2
// have to return +ve if o1 has to come after o2
// have to return 0 if o1 is equal to o2
}
This article is contributed by Gaurav Miglani. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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