w55

src/w6/Main.java

@@ -0,0 +1,50 @@
+package w6;
+
+// 游泳接口
+interface Swimmable {
+    void swim();
+}
+
+// 抽象动物类
+abstract class Animal {
+    public abstract void makeSound();
+}
+
+// 狗：继承Animal + 实现游泳接口
+class Dog extends Animal implements Swimmable {
+    @Override
+    public void makeSound() {
+        System.out.println("小狗汪汪汪叫");
+    }
+
+    @Override
+    public void swim() {
+        System.out.println("小狗会游泳，正在游泳");
+    }
+}
+
+// 猫：只继承Animal，不实现游泳接口
+class Cat extends Animal {
+    @Override
+    public void makeSound() {
+        System.out.println("小猫喵喵喵叫");
+    }
+}
+
+// 主类名改成Main！和文件名Main.java完全一致
+public class Main {
+    public static void main(String[] args) {
+        // 多态测试：父类引用指向子类对象
+        Animal animal1 = new Dog();
+        Animal animal2 = new Cat();
+
+        // 多态调用叫声
+        animal1.makeSound();
+        animal2.makeSound();
+
+        // 向下转型调用游泳方法
+        if (animal1 instanceof Dog dog) {
+            dog.swim();
+        }
+    }
+}

src/w8/Main.java

@@ -0,0 +1,40 @@
+package w8;
+ public class Main {
+    public static void main(String[] args) throws InterruptedException {
+        // Pair test
+        Pair<String, Integer> pair = new Pair<>("age", 25);
+        System.out.println("Original: " + pair);
+        System.out.println("Swap: " + pair.swap());
+
+        // Cache test
+        Cache<String, String> cache = new Cache<>(3000);
+        cache.put("name", "Ahmed");
+        System.out.println("Cache get: " + cache.get("name"));
+    }
+}
+
+class Pair<K, V> {
+    private K key;
+    private V value;
+    public Pair(K key, V value) { this.key = key; this.value = value; }
+    public Pair<V, K> swap() { return new Pair<>(value, key); }
+    public String toString() { return "Pair{" + key + "," + value + "}"; }
+}
+
+class Cache<K, V> {
+    private java.util.HashMap<K, CacheEntry<V>> cache = new java.util.HashMap<>();
+    private long defaultExpireTime;
+    public Cache(long t) { this.defaultExpireTime = t; }
+    public void put(K key, V value) {
+        cache.put(key, new CacheEntry<>(value, defaultExpireTime > 0 ? System.currentTimeMillis() + defaultExpireTime : 0));
+    }
+    public V get(K key) {
+        CacheEntry<V> entry = cache.get(key);
+        if (entry == null || (entry.expireTime > 0 && System.currentTimeMillis() > entry.expireTime)) return null;
+        return entry.value;
+    }
+    private static class CacheEntry<V> {
+        V value; long expireTime;
+        CacheEntry(V v, long e) { value = v; expireTime = e; }
+    }
+}