Java Program to Move All Uppercase Characters to the End

Last Updated : 31 Mar, 2023

Given a string that contains uppercase letters as well as lower case letters. The task is to move all uppercase characters at the end of the String. The uppercase characters must be in the same order as in the original string.

Input    : "heLLGFg"
Output   : "hegLLGF"

Input    : "Hello"
Output   : "elloH"

Here we are having two different approaches to get to the problem namely as follows:

Using ASCII values of the characters.
Using queue data structures

Approach 1: Using ASCII values of the characters.

Iterate the character of the string one by one and checks the ASCII values of the respective character of the string.
For all uppercase letters, ASCII values lie under [65-90] char values. Store the characters of these ASCII values in the String variable and print the string at the end of the Iteration.

Example:

Java

// Java Program to Move All Uppercase Characters to the End
 
// Importing input output classes
import java.io.*;
 
// Mai class
class GFG {
 
    // Method 1
    // To shift uppercase characters
    static void shiftuppercase(String m, int length)
    {
 
        // Taking an empty string
        String temp = "";
 
        for (int i = 0; i < length; ++i) {
 
            // Condition check
            // If the character is uppercase via
            // the ASCII values of the  character
            if (m.charAt(i) >= 65 && m.charAt(i) <= 90) {
                temp += m.charAt(i);
            }
 
            // The character is already lowercase
            else
                System.out.print(m.charAt(i));
        }
 
        // Now, Printing the uppercase string
        System.out.print(temp);
    }
 
    // Method 2
    // Main driver method
    public static void main(String[] args)
    {
        // Custom input string
        String m = "heLLGFg";
 
        // Computing the length of the string
        // using length() method
        int length = m.length();
 
        // Calling the method 1 over the custom string taken
        // above to move all uppercase char to the end
        shiftuppercase(m, length);
    }
}

Output:

Time Complexity: O(n) //n is the length of the string.

Space Complexity: O(1)

Approach 2: Using queue data structures

Queue Data structure implements the First in First out concept, We use this concept and store the uppercase characters in the queue.
Print all the characters except the uppercase characters.
After the iteration removes all the elements from the queue.

Example:

Java

// Java Program to Move All Uppercase Characters to the End
// Using Queue data structures 
 
// Importing input output classes
import java.io.*;
// Importing utility classes
import java.util.*;
 
// Main class
class GFG {
 
    // Method 1
    // Main driver method
    static void shiftuppercase(String m, int length)
    {
        // Creating an object of Queue class of character
        // type
        Queue<Character> Q = new LinkedList<Character>();
 
        // Declaring an initializing to empty string
        String temp = "";
 
        for (int i = 0; i < length; ++i) {
 
            // Condition checkfor the uppercase characters
            // If uppercase use ASCII values of the
            // character
            if (m.charAt(i) >= 65 && m.charAt(i) <= 90) {
                Q.add(m.charAt(i));
            }
 
            // Character is lowercase
            else
 
                // Leave it ascites on its index
                System.out.print(m.charAt(i));
        }
 
        // Now, printing the uppercase string till
        // there are elements in queue
        while (Q.size() != 0) {
 
            // Removing all the elements from the queue
            System.out.print(Q.peek());
 
            // Clear the queue
            Q.remove();
        }
    }
 
    // Method 2
    // main driver method
    public static void main(String[] args)
    {
 
        // Given input string
        String m = "heLLGFg";
 
        //  Computing the length of the string
        // using length() method
        int length = m.length();
 
        // Calling the
        shiftuppercase(m, length);
    }
}

Output:

Time Complexity: O(N) // where N is the length of the given string.

Auxiliary Space: O(n)

Approach 3 : Using isUpperCase() method

Java

// Java Program to Move All Uppercase Characters
// to the End
 
// Importing input output classes
import java.io.*;
 
// Main class
class GFG {
 
    public static void main(String[] args)
    {
        // Custom input string
        String m = "heLLGFg";
        String newstr = "";
        String upper = "";
        for (int i = 0; i < m.length(); i++) {
            if (Character.isUpperCase(m.charAt(i))) {
                upper += m.substring(i, i + 1);
            }
            else {
                newstr += m.substring(i, i + 1);
            }
        }
        System.out.println(newstr + upper);
    }
}