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import java.awt.*;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* Examples taken from <a href="https://openjdk.org/jeps/443">JEP 443</a>
*/
public class UnnamedPatternsPreview1Aspect {
public static void main(String[] args) {}
before() : execution(* main(String[])) {
System.out.println(thisJoinPoint);
// An enhanced for loop with side effects
int acc = 0;
final int LIMIT = 2;
for (Order _ : List.of(new Order(), new Order(), new Order())) {
if (acc < LIMIT)
acc++;
}
System.out.println(acc);
// The initialisation of a basic for loop can declare unnamed local variables
for (int i = 0, _ = sideEffect(); i < 2; i++) {
System.out.println(i);
}
// An assignment statement, where the result of the expression on the right hand side is not needed
Queue<Integer> q = new PriorityQueue<>(List.of(1, 2, 3, 4, 5, 6));
while (q.size() >= 3) {
var x = q.remove();
var y = q.remove();
var _ = q.remove();
System.out.println(new Point(x, y));
}
// The same unnamed variable name '_' can be used in multiple assignment statements
q = new PriorityQueue<>(List.of(1, 2, 3, 4, 5, 6));
while (q.size() >= 3) {
var x = q.remove();
var _ = q.remove();
var _ = q.remove();
System.out.println(new Point(x, 0));
}
// Unnamed variables can be used in one or multiple catch blocks
String s = "123xy";
try {
int i = Integer.parseInt(s);
System.out.println(i);
} catch (NumberFormatException _) {
System.out.println("Bad number: " + s);
} catch (Exception _) {
System.out.println("Unexpected error");
}
// Try with resources
try (var _ = ScopedContext.acquire()) {
System.out.println("Doing something within scoped context");
}
// A lambda whose parameter is irrelevant
System.out.println(
Stream.of("one", "two", "three")
.collect(Collectors.toMap(String::toUpperCase, _ -> "NODATA"))
);
}
static int sideEffect() {
System.out.println("side effect");
return 42;
}
static class Order {}
static class ScopedContext implements AutoCloseable {
public static ScopedContext acquire() {
return new ScopedContext();
}
@Override
public void close() {
System.out.println("Closing scoped context");
}
}
}
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