Update Exercise11.java

Here is my solution:
for (int i = 0; i < (take.length() - 1); i = i + 2 ) {
                ch[i] = take.charAt(i+1);
                ch[i+1] = take.charAt(i);
            }
            if (take.length()%2 != 0) {
                ch[take.length() - 1] = take.charAt(take.length() - 1);
            }