Find nested parenthesis recursively

NestedParenthesis.java

public boolean nestParen(String str) {
  int i= str.indexOf('('), j=str.lastIndexOf(')');
  if(i==-1 ^ j==-1){
    return false;
  }
  if(i==-1 && j==-1)
    return true;
  return nestParen(str.substring(i+1,j));
}