Improve error reporting

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>
Avoid setting static field from instance method

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>
Check for null in the equals method

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>
Ensure that the jar file is closed.

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>
Disable Sonar check.

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>