Skip to content

Instantly share code, notes, and snippets.

@nbenns
Created October 20, 2018 20:49
Show Gist options
  • Save nbenns/f11aac2461f6da22ca78f78de06bf467 to your computer and use it in GitHub Desktop.
Save nbenns/f11aac2461f6da22ca78f78de06bf467 to your computer and use it in GitHub Desktop.
Transition to Option
import java.util.function.Function;
public abstract class Option<T> {
private static class Some<T> extends Option<T> {
private T val;
Some(final T val) {
this.val = val;
}
@Override
public String toString() {
return "Some<" +
this.val
.getClass()
.toString()
.split(" ")[1] +
">(" + this.val + ")";
}
@Override
public <R> Option<R> ifNotNull(Function<T, Option<R>> f) {
return f.apply(val);
}
}
private static class None<T> extends Option<T> {
None() {}
@Override
public <R> Option<R> ifNotNull(Function<T, Option<R>> f) {
return new None<>();
}
@Override
public String toString() {
return "Nothing()";
}
}
private Option() { }
public static <T> Option<T> from(final T t) {
if (t == null) return None();
else return Some(t);
}
public static <T> Option<T> Some(final T t) {
return new Some<T>(t);
}
public static <T> Option<T> None() {
return new None<T>();
}
public abstract <R> Option<R> ifNotNull(final Function<T, Option<R>> f);
}
public class Main {
static Integer intVar(String input) {
if (input == null) return null;
else {
try {
return Integer.parseInt(input);
} catch (NumberFormatException ex) {
return null;
}
}
}
static Integer checkValid(Integer i) {
if (i == null) return null;
else {
if ((i > 0) && (i < 10)) return i;
else return null;
}
}
public static void main(String[] args) {
String myIntVar = System.getenv("MYINTVAR");
Integer iVar = intVar(myIntVar);
Integer validVar = checkValid(iVar);
System.out.println(validVar);
}
}
public class Main {
static Integer intVar(String input) {
try {
return Integer.parseInt(input);
} catch (NumberFormatException ex) {
return null;
}
}
static Integer checkValid(Integer i) {
if ((i > 0) && (i < 10)) return i;
else return null;
}
public static void main(String[] args) {
String myIntVar = System.getenv("MYINTVAR");
if (myIntVar != null) {
Integer iVar = intVar(myIntVar);
if (iVar != null) {
Integer validVar = checkValid(iVar);
System.out.println(validVar);
}
}
}
}
public class Main {
static Option<Integer> intVar(String input) {
try {
return Option.Some(Integer.parseInt(input));
} catch (NumberFormatException ex) {
return Option.None();
}
}
static Option<Integer> checkValid(Integer i) {
if ((i > 0) && (i < 10)) return Option.Some(i);
else return Option.None();
}
public static void main(String[] args) {
Option<String> myIntVar = Option.from(System.getenv("MYINTVAR"));
Option<Integer> iVar = myIntVar.ifNotNull(Main::intVar);
Option<Integer> validVar = iVar.ifNotNull(Main::checkValid);
System.out.println(validVar);
}
}
public class Main {
static Option<Integer> intVar(String input) {
try {
return Option.Some(Integer.parseInt(input));
} catch (NumberFormatException ex) {
return Option.None();
}
}
static Option<Integer> checkValid(Integer i) {
if ((i > 0) && (i < 10)) return Option.Some(i);
else return Option.None();
}
public static void main(String[] args) {
Option<Integer> validVar =
Option.from(System.getenv("MYINTVAR"))
.ifNotNull(Main::intVar)
.ifNotNull(Main::checkValid);
System.out.println(validVar);
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment