Unexpected Type errors

Question

I\'m getting two small unexpected type errors which I\'m having trouble trying to solve.

The errors occur at:

swapped.charAt(temp1) = str.charAt(temp2);
         


        

Answer 1

You can assign values to variables, not other values. Statements like 5 = 2 or 'a' = 'z' don't work in Java, and that's why you're getting an error. swapped.charAt(temp1) returns some char value you're trying to overwrite, it's not a reference to a particular position inside the String or a variable you can alter (also, mind that Java Strings are immutable so you can't really change them in any way after creation).

Refer to http://docs.oracle.com/javase/7/docs/api/java/lang/String.html for information on using String, it should have a solution for what you're trying to do.

Your code may even throw IndexOutOfBoundsException - if the index argument is negative or not less than the length of this string. Check the length of each string.

Answer 2

Description of String#charAt(int):

Returns the char value at the specified index

It returns the value of the character; assigning values to that returned value in the following lines is the problem:

swapped.charAt(temp1) = str.charAt(temp2);
swapped.charAt(temp2) = temp1;

Also, String#charAt(int) expects an index of a character within the String, not the character itself (i.e. chatAt(temp1) is incorrect), so your method will not work as expected even if you fix the former problem.

Try the following:

String swapped;
if(swap1 > swap2) {
    swap1+=swap2;
    swap2=swap1-swap2;
    swap1-=swap2;
}
if(swap1!=swap2)
    swapped = str.substring(0,swap1) + str.charAt(swap2) + str.substring(swap1, swap2) + str.charAt(swap1) + str.substring(swap2);

Answer 3

The left side of your assignment cannot receive that value.