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集合-数据结构相关.md

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+# 集合：
+
+**总结：**
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20250417165937735.png" alt="image-20250417165922953" style="zoom:50%;" />
+
+其中Collection接口中又分为**set**接口和**list**接口
+
+## Collection:
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20250417165721995.png" alt="image-20250417165713561" style="zoom:50%;" />
+
+**注意事项：**
+
+remove and contains方法依赖于底层equals方法
+
+## 集合通用遍历方法：
+
+### 1.迭代器  2.增强for循环  3.forEach
+
+首先获取迭代器：
+
+`Iterator<Student> it = c.iterator();`
+
+其次判断循环是否还有元素
+
+`hasNext()方法`    `next()方法`    
+
+注意：next()方法只调用一次，要不然会引起指针异常
+
+### 迭代器源码解析：
+
+![image-20250420172303418](https://gitee.com/icecat2233/picture/raw/master/20250420172317333.png)
+
+### **三种方法演示：**
+
+```java
+public class Test2 {
+    public static void main(String[] args) {
+        Collection<Student> c = new ArrayList<>();
+        c.add(new Student("小鸟游六花",15));
+        c.add(new Student("小鸟游七花",15));
+        c.add(new Student("小鸟游八花",15));
+
+        //迭代器循环
+        Iterator<Student> it = c.iterator();
+
+        while (it.hasNext()){
+            Student stu = it.next();
+            System.out.println(stu.getName()+"---"+stu.getAge());
+        }
+
+        //增强for循环
+        for (Student stu:c){
+            System.out.println(stu);
+        }
+
+        //forEach遍历
+        c.forEach(student -> System.out.println(student));
+    }
+}
+```
+
+# List集合
+
+## list集合特点以及方法
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20250425155619805.png" alt="image-20250425155604336" style="zoom:67%;" />
+
+## 并发修改异常：
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20250425154636875.png" alt="image-20250425154628294" style="zoom: 80%;" />
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20250425155719001.png" alt="image-20250425155717100" style="zoom:80%;" />
+
+## List集合的5种遍历方式
+
+1. Iterator迭代器
+2. 增强for循环
+3. foreach
+4. 普通for循环
+5. ListIterator迭代器
+
+# 数据结构：栈 队列 链表 数组
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20250425163326284.png" alt="image-20250425163323615" style="zoom: 67%;" />
+
+## 其中Arraylist集合扩容机制为
+
+1. 在初始化时长度为0
+2. 调用添加方法add时长度为10
+3. 此后长度超过10时，会将数组长度增加原来的1/2
+
+#### **源码分析**：**此为长度还未超出10时的源码过程**
+
+![image-20250425165520793](https://gitee.com/icecat2233/picture/raw/master/20250425165535349.png)
+
+####          **此为超出10时源码过程**：
+
+![image-20250425165743512](imgh/image-20250425165743512.png)
+
+## LinkedList特有方法
+
+removeFirst()   removeLast()