Program that reads args and transforms all letters in capital letters without the use of toUpperCase()

Question

So, I'm trying to make a program that reads args and transforms all letters in capital letters without the use of toUpperCase(). The only way I have to use to process the single letters is with " - 'a' + 'A' "

This is what I did so far

import java.util.Scanner;

public class ArgsTest{
    public static void main(String args[]){

for(int i = 0; i<args.length; i++){
    for(int y=0; y<args[i].length(); y++){
    if ('a' <= args[i].charAt(y) && args[i].charAt(y) <= 'z') {
        args[i].charAt(y) = (char)(args[i].charAt(y) - 'a' + 'A');}  
    }
}

}

}

I don't understand what I'm doing wrong, the error says:

ArgsTest.java:9: error: unexpected type
        args[i].charAt(y) = (char)(args[i].charAt(y) - 'a' + 'A');
                      ^
  required: variable
  found:    value
  1 error

Possible duplicate of https://stackoverflow.com/questions/41154081/how-to-convert-a-string-to-uppercase-without-using-the-touppercase-method — Sudhir Ojha, Jan 18 '19 at 10:05
You can find your answer here https://stackoverflow.com/questions/6952363/replace-a-character-at-a-specific-index-in-a-string — some IT dood, Jan 18 '19 at 10:28

score 2 · Answer 1 · answered Jan 18 '19 at 10:01

args[i].charAt(y) returns a character not a variable, so you can not assign a value to it

What you should do is creating a new String and add the uppercase charater to this and print it out:

    for(int i = 0; i<args.length; i++){
        String result = "";
        for(int y=0; y<args[i].length(); y++){
        if ('a' <= args[i].charAt(y) && args[i].charAt(y) <= 'z') {
            result  += (char)(args[i].charAt(y) - 'a' + 'A');}  
        }
        System.out.println(result);
    }

Deepak Kumar · Answer 2 · 2019-01-18T10:21:32.033

0

The charAt() method returns character not a variable. So you can't assign a value to a character. In java We can only assign value to a variable not to a value.

for(int i = 0; i<args.length; i++){
    String s = "";
    for(int y=0; y<args[i].length(); y++){
        if ('a' <= args[i].charAt(y) && args[i].charAt(y) <= 'z') {
            s+=(char)(args[i].charAt(y) - 'a' + 'A');
        }  
    }
    args[i]=s;
}

edited Jan 18 '19 at 10:21

answered Jan 18 '19 at 10:05

Deepak Kumar

1,246
14
38

Do not answer like *Try like this* explain what you have done and why – Jens Jan 18 '19 at 10:07

Program that reads args and transforms all letters in capital letters without the use of toUpperCase()

2 Answers2