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Noncompliant Code Example

This The isCapitalized() method in this noncompliant code example accepts a string and returns true when it consists of a capital letter followed by lowercase letters. To handle corner cases, it checks for various exceptional conditions and throws exceptions when they are likely to disrupt normal operationThe method also throws null a RuntimeException when passed a null string argument.

boolean isCapitalized(String s) {
  if (s == null) {
    throw new RuntimeException("Null String");
  }
  if (s.equals("")) {
    return true;
  }
  String first = s.substring(0, 1);
  String rest = s.substring(1);
  return (first.equals(first.toUpperCase()) &&
          rest.equals(rest.toLowerCase()));
}

A calling method must violate also rule ERR14-J. Do not catch RuntimeException to handle null string arguments to the methoddetermine if the RuntimeException was thrown.

Compliant Solution

This compliant solution throws a specific exception the (NullPointerException) to denote the particular specific exceptional condition.

boolean isCapitalized(String s) {
  if (s == null) {
    throw new NullPointerException();
  }
  if (s.equals("")) {
    return true;
  }
  String first = s.substring(0, 1);
  String rest = s.substring(1);
  return (first.equals(first.toUpperCase()) &&
          rest.equals(rest.toLowerCase()));
}

Note that the null check is redundant; if it were removed, the next call (s.equals("")) would will throw a NullPointerException if when s were is null. However, the explicit null check is good form, because it explicitly indicates the programmer's intent. More complex code may require explicit testing of invariants and appropriate throw statements.

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