45 query = "SELECT * FROM Books WHERE author LIKE '%" + bookauthor + "%'";
46 } else if (bookread != null) {
47 // Filter by if the book has been read or not
48 Integer read = bookread ? 1 : 0;49 query = "SELECT * FROM Books WHERE read = '" + read.toString() + "'";
50 } else {
51 // All books73 try (PreparedStatement prepStmt = connection.prepareStatement(query);) {
74 prepStmt.setString(1, book.name);
75 prepStmt.setString(2, book.author);
76 prepStmt.setInt(3, book.read? 1 : 0);77
78 prepStmt.executeUpdate();
79 A boxed boolean value (java.lang.Boolean) is being used in a potentially dangerous manner. Such usage may lead to a NullPointerException being thrown.
Java's primitive types differ from normal classes in that primitives can never be null. However, classes can be null, even primitive wrapper classes such as Boolean or Character. For Boolean in particular, this means that turning a boolean into a Boolean promotes it from a binary true or false to a ternary true, false or null. This may be undesirable in most cases, and is worth avoiding.
The nullability of wrapper types becomes an issue when the wrapper types are used directly in expressions without null checks.
Bad Practice
In the example below, the if statement evaluates the value of nullable when its value is null. This will lead to a NullPointerException being thrown.
Boolean nullable = null
if (nullable) { // This would throw a NullPointerException.
// ...
}
Recommended
You could perform an explicit comparison with the required value.
if (nullable == true) {
// ...
}
// OR
if (Boolean.TRUE.equals(nullable)) {
// ...
}
Using Boolean.TRUE here can prevent an unnecessary unboxing conversion when performing a comparison.