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