From b26992411a2a9bc17ed022d8a67502654c3bce8e Mon Sep 17 00:00:00 2001
From: wangjiashuo <1443062665@qq.com>
Date: Sun, 31 May 2026 13:32:25 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20w8=20=E6=B3=9B=E5=9E=8B?=
 =?UTF-8?q?=E7=BB=83=E4=B9=A0=EF=BC=88Pair=20=E4=B8=8E=20Cache=EF=BC=89?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 w8/Cache.class   | Bin 0 -> 2322 bytes
 w8/Cache.java    |  50 +++++++++++++++++++++++++++++++++++++++++++++++
 w8/Pair.class    | Bin 0 -> 1981 bytes
 w8/Pair.java     |  46 +++++++++++++++++++++++++++++++++++++++++++
 w8/思考题.txt |  15 ++++++++++++++
 5 files changed, 111 insertions(+)
 create mode 100644 w8/Cache.class
 create mode 100644 w8/Cache.java
 create mode 100644 w8/Pair.class
 create mode 100644 w8/Pair.java
 create mode 100644 w8/思考题.txt

diff --git a/w8/Cache.class b/w8/Cache.class
new file mode 100644
index 0000000000000000000000000000000000000000..d5e47bf81851c43aee01c8ae73c67078a1950904
GIT binary patch
literal 2322
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literal 0
HcmV?d00001

diff --git a/w8/Cache.java b/w8/Cache.java
new file mode 100644
index 0000000..3715efa
--- /dev/null
+++ b/w8/Cache.java
@@ -0,0 +1,50 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class Cache<K, V> {
+    private final Map<K, V> cache;
+
+    public Cache() {
+        this.cache = new HashMap<>();
+    }
+
+    public void put(K key, V value) {
+        cache.put(key, value);
+    }
+
+    public V get(K key) {
+        return cache.get(key);
+    }
+
+    public boolean containsKey(K key) {
+        return cache.containsKey(key);
+    }
+
+    public void remove(K key) {
+        cache.remove(key);
+    }
+
+    public void clear() {
+        cache.clear();
+    }
+
+    public int size() {
+        return cache.size();
+    }
+
+    public static void main(String[] args) {
+        Cache<String, Integer> studentCache = new Cache<>();
+
+        studentCache.put("张三", 18);
+        studentCache.put("李四", 20);
+
+        System.out.println("张三的年龄：" + studentCache.get("张三"));
+        System.out.println("缓存是否包含王五：" + studentCache.containsKey("王五"));
+
+        studentCache.remove("李四");
+        System.out.println("移除李四后缓存大小：" + studentCache.size());
+
+        studentCache.clear();
+        System.out.println("清空后缓存大小：" + studentCache.size());
+    }
+}
diff --git a/w8/Pair.class b/w8/Pair.class
new file mode 100644
index 0000000000000000000000000000000000000000..e8b070cf79de3ad4cd4ddc059114cb96e8e2bcc0
GIT binary patch
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literal 0
HcmV?d00001

diff --git a/w8/Pair.java b/w8/Pair.java
new file mode 100644
index 0000000..7b07754
--- /dev/null
+++ b/w8/Pair.java
@@ -0,0 +1,46 @@
+public class Pair<K, V> {
+    private K key;
+    private V value;
+
+    public Pair(K key, V value) {
+        this.key = key;
+        this.value = value;
+    }
+
+    public K getKey() {
+        return key;
+    }
+
+    public void setKey(K key) {
+        this.key = key;
+    }
+
+    public V getValue() {
+        return value;
+    }
+
+    public void setValue(V value) {
+        this.value = value;
+    }
+
+    public void swap() {
+        Object temp = key;
+        key = (K) value;
+        value = (V) temp;
+    }
+
+    @Override
+    public String toString() {
+        return "Pair{" +
+                "key=" + key +
+                ", value=" + value +
+                '}';
+    }
+
+    public static void main(String[] args) {
+        Pair<String, Integer> pair = new Pair<>("年龄", 20);
+        System.out.println("交换前：" + pair);
+        pair.swap();
+        System.out.println("交换后：" + pair);
+    }
+}
diff --git a/w8/思考题.txt b/w8/思考题.txt
new file mode 100644
index 0000000..6a010f8
--- /dev/null
+++ b/w8/思考题.txt
@@ -0,0 +1,15 @@
+为什么Java泛型不支持基本类型？
+ 
+核心原因是Java泛型的类型擦除机制，以及基本类型和引用类型的存储方式差异，具体分为以下几点：
+ 
+1. 类型擦除导致的兼容问题
+Java泛型在编译后会被擦除为  Object （或上界类型），而基本类型（如  int 、 double ）不是  Object  的子类，无法直接赋值给  Object 。如果允许泛型使用基本类型，擦除后的代码会出现类型不匹配的问题。
+​
+2. 自动装箱/拆箱的本质
+虽然我们可以用  List<Integer>  间接实现“存储int”的效果，但这并不是直接支持基本类型，而是利用了自动装箱（autoboxing）机制：编译器会自动将  int  转换为  Integer （包装类），本质上存储的还是引用类型。
+​
+3. 内存模型差异
+基本类型存储在栈中，占用固定大小的内存（如  int  占4字节）；而引用类型存储在堆中，栈中仅保存对象的引用。如果泛型直接支持基本类型，JVM需要为每个基本类型生成不同的类实现，会导致类爆炸，违背了泛型“一份代码，多种类型”的设计初衷。
+​
+4. 历史兼容考虑
+Java泛型是在JDK 1.5引入的，为了兼容之前的非泛型代码（如  ArrayList ），采用了擦除实现。如果直接支持基本类型，会打破这种向后兼容性，导致旧代码无法运行。
\ No newline at end of file