Java Unexpected type error

Question

I am trying to create a method that will consume two Strings. It will Compare String 1 with String 2 and will replace all unfound chars with '_'. For example if String 1 = "Hello"; String 2 = "eo" then the method will return String 1 as "_e__o" Here is my code:

static String getRevealedChars (String s1, String s2)
{
    for (int i = 0; i < s1.length(); i++)
    {
        for (int c = 0; c < s2.length(); c++)
        {
            if (s1.charAt(i) == s2.charAt(c))
            {
                break;
            }
            else 
            {
                // this is where I get my Error
                s1.charAt(i) = '_';
            }
        }
    }
}

However, when I run this code I get a "unexpected type" error at s1.charAt(i) = '_';. I'm really new to java, thanks in advance.

Key point - `String` objects are immutable. So you can't change your `String` _in situ_ - you'll have to make a brand new `String` to return. You might find it easiest to build a `char[]` and convert it to `String` at the end. — Dawood ibn Kareem, Jan 29 '17 at 06:21
i tried creating an array but i dont know how to keep adding char values into an array — gurnii, Jan 29 '17 at 06:43

score 0 · Answer 1 · edited Jan 29 '17 at 11:31

Replace datatype of s1 and s2 from String to StringBuilder, then use setCharAt() instead of charAt() as follows:

StringBuilder s1 = new StringBuilder("hello");
StringBuilder s2 = new StringBuilder("eo");

static String getRevealedChars (StringBuilder s1, StringBuilder s2)
{
    for (int i = 0; i < s1.length(); i++)
    {
        for (int c = 0; c < s2.length(); c++)
        {
            if (s1.charAt(i) == s2.charAt(c))
            {
                break;
            }
            else 
            {
                // this is where I corrected Error
                s1.setCharAt(i, '_');
            }
        }
    }
}

Hope this helps. Good luck.

Java Unexpected type error

1 Answers1