Local Variable Type Inference Examples

LocalVariableTypeInferenceTest.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;

public class LocalVariableTypeInferenceTest {

    private void processOrder(String order) {
        System.out.println(order);
    }

    public static void main(String[] args) throws Exception {
        // local variable use
        var test = new LocalVariableTypeInferenceTest();

        // infers HashSet<String> vs Set<String> orders = new HashSet<>();
        var orders = new HashSet<String>();

        // indexed for-loop use
        for (var i = 0; i < 5; i++) {
            orders.add(UUID.randomUUID().toString());
        }

        // for-each use
        for (var order : orders) {
            // process an order
            test.processOrder(order);
        }

        // infers Stream<String>
        var stream = orders.stream();
        stream.forEachOrdered(test::processOrder);

        // try-with-resources use
        try (var in = Files.newInputStream(Paths.get("./src/LocalVariableTypeInferenceTest.java")); var reader = new BufferedReader(new InputStreamReader(in))) {
            // print the imports
            reader.lines().takeWhile(e -> !e.startsWith("public")).forEachOrdered(System.out::println);
        } catch (IOException e) {
            throw e;
        }
    }
}