Compile error: Incompatible operand types java.lang.String and char

Question

import java.io.*;
import hsa.Console;
import java.awt.*;


    public static void main(String[] args) throws IOException {
        c = new Console();

        String sentence;
        String encrypt = "";
        String vowels = "AEIOUaeiou";
        final String PUNCTAUTION = ".,;?!\"\\/\' -";
        StringBuffer removePunctation = new StringBuffer();
        StringBuffer thirdLetters = new StringBuffer();

        char tempChar;

        //Open The Output File

        PrintWriter output;
        output = new PrintWriter(new FileWriter("output.txt"));

        c.println("Please enter the sentence you would like to encrypt");
        sentence = c.readLine();


        for (int i = 0; i < sentence.length(); i++) {
            tempChar = sentence.charAt(i);

            if (PUNCTAUTION.indexOf(tempChar) == -1) {
                encrypt = encrypt + tempChar;
            }
        }
        if (encrypt == 'A') {
            sentence.replace('A', '!');
        } else if (encrypt == 'I') {
            sentence.replace('I', '#');
        } else if (encrypt == 'E') {
            sentence.replace('E', '@');
        } else if (encrypt == 'O') {
            sentence.replace('O', '$');
        } else if (encrypt == 'U') {
            sentence.replace('U', '%');
        }
        c.println(encrypt.toString().toUpperCase());

        output.println(encrypt.toString().toUpperCase());
    }

I'm trying to remove all punctuation and spaces, and change the vowels AEIOU to !@#$%, but I'm getting an error. I am also trying to output the vowels I replaced from the sentence at the bottom and reverse them.

Answer 1

To test strings for equality, use String.equals(). For example, "A".equals(encrypt) tests if the string encrypt is the capital letter A.

Notice that, as above, it is preferable to put the constant string first (instead of encrypt.equals("A")) to avoid the possibility of a null pointer exception.

If you want case-insensitive matching, there's also String.equalsIgnoreCase().

---

And regarding your task at hand (e.g., remove/replace all occurrences of something), you might consider using regular expressions instead.

For example, to replace all capital letter A with ! you could use something like:

encrypt.replaceAll("A", "!")

Or, if you'll be using the same regular expression pattern over and over again or want the flexibility to make case-insensitive patterns, then:

Pattern a = Pattern.compile("A", Pattern.CASE_INSENSITIVE);
...
a.matcher(encrypt).replaceAll("!");