Verify special char is in String before append into StringBuffer

Question

I have following code to verify A special char "X" is in the String before continue adding it to a StringBuffer:
private boolean veriChar(String poem){
if(peom.indexOf("X")==-1) return false;// make sure X is in the String
return true
However, if I only want a single X in String to return true, any method to use? for example: poem=" EXTRA TEXT" (2 Xes here) needs to be rejected to be false.

Answer 1

take this code compile it and see for yourself.
public class Test{
  public static void main(String args[]){
    Test t = new Test();
    System.out.println(""+t.veriChar("MATT"));
    System.out.println(""+t.veriChar("MAX"));
    System.out.println(""+t.veriChar("MAXX"));
  private boolean veriChar(String toCheck){
    return!((toCheck.indexOf("X")<0)||(toCheck.indexOf("X")!=toCheck.lastIndexOf("X")));
} you will see that the first and third ones return false and the second returns true which is as you want.
now an explanation of what is happening.
the method looks like this
private boolean veriChar(String toCheck){
    return!((toCheck.indexOf("X")<0)||(toCheck.indexOf("X")!=toCheck.lastIndexOf("X")));
  }first we check if the special X or whatever exists in the string at all
toCheck.indexOf("X")<0;this returns true for the first test of MATT
now we check if the last occurance in our string of the special X is the same position as the first occurance. if it is then we have only one special X. if not then we have more than one special X.
toCheck.indexOf("X")!=toCheck.lastIndexOf("X")note that we check for not equals so that for MAX it returns false and for MAXX it returns true
so now we have our answers but they are inverted from what we want so we put the ! which gives the boolean opposite. so that the MAX returns true and the other two return false.