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import org.checkerframework.checker.units.UnitsTools;
import org.checkerframework.checker.units.qual.Prefix;
import org.checkerframework.checker.units.qual.s;
import qual.Frequency;
import qual.Hz;
import qual.kHz;
class UnitsExtensionDemo {
@Hz int frq;
void bad() {
// Error! Unqualified value assigned to a @Hz value.
// :: error: (assignment.type.incompatible)
frq = 5;
// suppress all warnings issued by the units checker for the d1 assignment statement
@SuppressWarnings("units")
@Hz int d1 = 9;
// specifically suppress warnings related to any frequency units for the d2 assigment
// statement
@SuppressWarnings("frequency")
@Hz int d2 = 10;
}
// specifically suppresses warnings for the hz annotation for the toHz method
@SuppressWarnings("hz")
static @Hz int toHz(int hz) {
return hz;
}
void good() {
frq = toHz(9);
@s double time = 5 * UnitsTools.s;
@Hz double freq2 = 20 / time;
}
void auto(@s int time) {
// The @Hz annotation is automatically added to the result
// of the division, because we provide class FrequencyRelations.
frq = 99 / time;
}
public static void main(String[] args) {
@Hz int hertz = toHz(20);
@s int seconds = 5 * UnitsTools.s;
@SuppressWarnings("units")
@s(Prefix.milli) int millisec = 10;
@SuppressWarnings("hz")
@kHz int kilohertz = 30;
@Hz int resultHz = hertz + 20 / seconds;
System.out.println(resultHz);
@kHz int resultkHz = kilohertz + 50 / millisec;
System.out.println(resultkHz);
// this demonstrates the type hierarchy resolution: the common supertype of Hz and kHz is
// Frequency, so this statement will pass
@Frequency int okTernaryAssign = seconds > 10 ? hertz : kilohertz;
// on the other hand, this statement expects the right hand side to be a Hz, so it will fail
// :: error: (assignment.type.incompatible)
@Hz int badTernaryAssign = seconds > 10 ? hertz : kilohertz;
}
}
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