How to end the following loop without using the break function?

The following Java program is supposed to manipulate a string input by the user in such a way that the user will decide which character needs to be replaced with another and just the first character from the string should be replaced. For example, if the user enters the string "PUMP" and decides to replace "P" with "L", the program should output the following result: "LUMP" (notice that only the first "P" was replaced with "L")

NOTE: YOU CANNOT USE BREAK COMMAND TO STOP THE LOOP. IT IS PROHIBITED.

I have written the following program and I am not able to stop at replacing just the first character of the string:

import java.util.Scanner;
public class StringFun {

	public static void main(String[] args) {
		Scanner keyboard = new Scanner(System.in);
		
		System.out.println("Enter the string to be manipulated");
		String inString = keyboard.nextLine();
		String outString = "";
		
		//Replace the first character from the string entered by the user only
		System.out.println("Enter the character to replace");
		char oldCharF = keyboard.next().charAt(0);
		
		System.out.println("Enter the new character");
		char newCharF = keyboard.next().charAt(0);
		
		
		for(int index = 0;index < inString.length();index++) {
			if(inString.charAt(index) == oldCharF){
				outString = outString + newCharF;
				
			}
			else {
				outString = outString + inString.charAt(index);
			}
			
		}

		System.out.print("The new sentence is: "+outString);
		

	}

}

I keep getting this result from the above code:

Enter the string to be manipulated

PUMP

Enter the character to replace

P

Enter the new character

L

The new sentence is: LUML

One of the simplest ways to do this is by adding a counter to keep track of how many times the letter you want to change is encountered. Because your looking for the first occurrence of the letter, and only want one letter to change, you could do this:

• Add an integer variable named count and instantiate it to 0.
• Change the if condition in the for loop by adding "&& counter < 0"
• Add "count++" inside the body of the that same if condition.

This will increment the count variable on the first occurrence that the letter being changed has been encountered. Because count will now be equal to 1, it will restrict any other letters from being changed and will solve the issue you had before.

import java.util.Scanner;
public class StringFun {

    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        
        System.out.println("Enter the string to be manipulated");
        String inString = keyboard.nextLine();
        String outString = "";
        int count = 0; // variable that tracks number of letter occurrences
        
        //Replace the first character from the string entered by the user only
        System.out.println("Enter the character to replace");
        char oldCharF = keyboard.next().charAt(0);
        
        System.out.println("Enter the new character");
        char newCharF = keyboard.next().charAt(0);
        
        
        for(int index = 0;index < inString.length();index++) 
        {
            if(inString.charAt(index) == oldCharF && count < 1) //Condition filter 
            {
                outString = outString + newCharF;
                count++; //Increment counter
                
            }
            else
                outString = outString + inString.charAt(index);
  
        System.out.print("The new sentence is: "+outString);
    }
}

Not that you actually want a break; in your code anyways, to end your for loop without utilizing the break; statement all you need to do is utilize a boolean flag to indicate that the first character that is to be replaced has been found and processed, for example:

String inString = "PUMP";
char oldCharF = 'P';
char newCharF = 'L';
String outString = "";
    
boolean charFound = false;
for (int index = 0; index < inString.length(); index++) {
    char inChar = inString.charAt(index);
    /* Is the current character (inChar) what we're 
       looking for (oldCharF) AND (&&) is it NOT 
       found yet (!charFound)?       */
    if (inChar == oldCharF && !charFound) {
        // Yes, it's the one we want
        outString += newCharF;  // Append our alternate character to outString.
        charFound = true;       // Change flag to true.
    }
    /* No, it's not the character we want OR 
       the desired character has already been 
       processed.               */
    else {
        outString += inChar;
    }
}

// Display the result held in outString to Console Window...
System.out.println(outString);