АдовЪ код

boolean.java

// class definition
private final Boolean address;

// do something
if (address == null) {
    // ...
} else if (address == Boolean.TRUE) {
    // ...
} else if (address == Boolean.FALSE) {
    // ...
} else {
    throw new IllegalArgumentException("Boolean must be one of [null], [TRUE], [FALSE]");
}

DBConnector.java

public class DBConnector { 
    public GlobalSaver gs = new GlobalSaver(); 
    // ...
}

public class GlobalSaver { 
    private static DBConnector dbc = new DBConnector(); 
    // ...
}

// somewhere in test
@Test
void test() {
    // ...
    DBConnector dbc = new DBConnector();
    // ...
}