1. try-with-resources

class MyResource implements AutoCloseable {
    public void action() { System.out.print("action "); }
    public void close() { System.out.print("close "); }
}

public class Test4 {
    public static void main(String[] args) {
        try (MyResource r = new MyResource()) {
            r.action();
        }
    }
}

2. 泛型 (Generics)

import java.util.*;

public class Test5 {
    public static void main(String[] args) {
        List<Integer> list = Arrays.asList(1,2,3,4);
        List<?> l2 = list;
        // l2.add(5);   // 編譯錯誤
        System.out.println(l2.get(2));
    }
}