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小傅哥，文章代码更新。晚上好!
面经手册 · 第7篇《ArrayList也这么多知识？一个指定位置插入就把谢飞机面晕了！》
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‎.gitignore

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/interview.iml
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/interview-04/interview-04.iml
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/interview-07/interview-07.iml
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/interview-05/interview-05.iml

‎README.md

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4. [面经手册 · 第3篇《HashMap核心知识，扰动函数、负载因子、扩容链表拆分，深度学习》](https://bugstack.cn/interview/2020/08/07/%E9%9D%A2%E7%BB%8F%E6%89%8B%E5%86%8C-%E7%AC%AC3%E7%AF%87-HashMap%E6%A0%B8%E5%BF%83%E7%9F%A5%E8%AF%86-%E6%89%B0%E5%8A%A8%E5%87%BD%E6%95%B0-%E8%B4%9F%E8%BD%BD%E5%9B%A0%E5%AD%90-%E6%89%A9%E5%AE%B9%E9%93%BE%E8%A1%A8%E6%8B%86%E5%88%86-%E6%B7%B1%E5%BA%A6%E5%AD%A6%E4%B9%A0.html)
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5. [面经手册 · 第4篇《HashMap数据插入、查找、删除、遍历，源码分析》](https://bugstack.cn/interview/2020/08/13/%E9%9D%A2%E7%BB%8F%E6%89%8B%E5%86%8C-%E7%AC%AC4%E7%AF%87-HashMap%E6%95%B0%E6%8D%AE%E6%8F%92%E5%85%A5-%E6%9F%A5%E6%89%BE-%E5%88%A0%E9%99%A4-%E9%81%8D%E5%8E%86-%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90.html)
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6. [面经手册 · 第5篇《看图说话，讲解2-3平衡树「红黑树的前身」》](https://bugstack.cn/interview/2020/08/16/%E9%9D%A2%E7%BB%8F%E6%89%8B%E5%86%8C-%E7%AC%AC5%E7%AF%87-%E7%9C%8B%E5%9B%BE%E8%AF%B4%E8%AF%9D-%E8%AE%B2%E8%A7%A32-3%E5%B9%B3%E8%A1%A1%E6%A0%91-%E7%BA%A2%E9%BB%91%E6%A0%91%E7%9A%84%E5%89%8D%E8%BA%AB.html)
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7 [面经手册 · 第6篇《带着面试题学习红黑树操作原理，解析什么时候染色、怎么进行旋转、与2-3树有什么关联》](https://bugstack.cn/interview/2020/08/20/%E9%9D%A2%E7%BB%8F%E6%89%8B%E5%86%8C-%E7%AC%AC6%E7%AF%87-%E5%B8%A6%E7%9D%80%E9%9D%A2%E8%AF%95%E9%A2%98%E5%AD%A6%E4%B9%A0%E7%BA%A2%E9%BB%91%E6%A0%91%E6%93%8D%E4%BD%9C%E5%8E%9F%E7%90%86-%E8%A7%A3%E6%9E%90%E4%BB%80%E4%B9%88%E6%97%B6%E5%80%99%E6%9F%93%E8%89%B2-%E6%80%8E%E4%B9%88%E8%BF%9B%E8%A1%8C%E6%97%8B%E8%BD%AC-%E4%B8%8E2-3%E6%A0%91%E6%9C%89%E4%BB%80%E4%B9%88%E5%85%B3%E8%81%94.html)
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7. [面经手册 · 第6篇《带着面试题学习红黑树操作原理，解析什么时候染色、怎么进行旋转、与2-3树有什么关联》](https://bugstack.cn/interview/2020/08/20/%E9%9D%A2%E7%BB%8F%E6%89%8B%E5%86%8C-%E7%AC%AC6%E7%AF%87-%E5%B8%A6%E7%9D%80%E9%9D%A2%E8%AF%95%E9%A2%98%E5%AD%A6%E4%B9%A0%E7%BA%A2%E9%BB%91%E6%A0%91%E6%93%8D%E4%BD%9C%E5%8E%9F%E7%90%86-%E8%A7%A3%E6%9E%90%E4%BB%80%E4%B9%88%E6%97%B6%E5%80%99%E6%9F%93%E8%89%B2-%E6%80%8E%E4%B9%88%E8%BF%9B%E8%A1%8C%E6%97%8B%E8%BD%AC-%E4%B8%8E2-3%E6%A0%91%E6%9C%89%E4%BB%80%E4%B9%88%E5%85%B3%E8%81%94.html)
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8. [面经手册 · 第7篇《ArrayList也这么多知识？一个指定位置插入就把谢飞机面晕了！》](https://bugstack.cn/interview/2020/08/27/%E9%9D%A2%E7%BB%8F%E6%89%8B%E5%86%8C-%E7%AC%AC7%E7%AF%87-ArrayList%E4%B9%9F%E8%BF%99%E4%B9%88%E5%A4%9A%E7%9F%A5%E8%AF%86-%E4%B8%80%E4%B8%AA%E6%8C%87%E5%AE%9A%E4%BD%8D%E7%BD%AE%E6%8F%92%E5%85%A5%E5%B0%B1%E6%8A%8A%E8%B0%A2%E9%A3%9E%E6%9C%BA%E9%9D%A2%E6%99%95%E4%BA%86.html)

‎interview-03/interview-03.iml

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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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<orderEntry type="library" name="Maven: com.alibaba:fastjson:1.2.73" level="project" />
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<orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.13" level="project" />
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<orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
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</component>
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</module>

‎interview-05/src/main/java/T.java

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/**
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* 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
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* 公众号：bugstack虫洞栈
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* Create by 小傅哥(fustack) @2020
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*/
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public class T {
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}

‎interview-07/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>interview</artifactId>
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<groupId>org.itstack</groupId>
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<version>1.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>interview-07</artifactId>
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</project>

‎interview-07/src/test/java/org/itstack/interview/test/ApiTest.java

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package org.itstack.interview.test;
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import com.alibaba.fastjson.JSON;
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import org.junit.Test;
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import sun.net.idn.Punycode;
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import javax.sound.midi.Soundbank;
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import java.lang.reflect.Array;
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import java.util.*;
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public class ApiTest {
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public static void main(String[] args) {
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List<String> list = new ArrayList<String>(Collections.nCopies(9, "a"));
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System.out.println("初始化：" + list);
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list.add(2, "b");
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System.out.println("插入后：" + list);
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}
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@Test
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public void t2() {
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String[] strs = new String[10];
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strs[5] = "1";
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Arrays.asList();
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}
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@Test
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public void test_remove() {
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ArrayList<String> list = new ArrayList<String>();
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list.add("a");
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list.add("b");
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list.add("c");
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list.add("d");
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list.add("e");
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list.add("f");
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list.add("g");
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list.add("h");
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list.add("i");
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list.add("j");
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System.out.println(list);
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list.remove(2);
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System.out.println(list);
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System.out.println(list.size());
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}
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@Test
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public void test_arraycopy() {
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int[] oldArr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
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int[] newArr = new int[oldArr.length + (oldArr.length >> 1)];
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System.arraycopy(oldArr, 0, newArr, 0, oldArr.length);
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newArr[11] = 11;
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newArr[12] = 12;
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newArr[13] = 13;
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newArr[14] = 14;
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System.out.println("数组元素：" + JSON.toJSONString(newArr));
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System.out.println("数组长度：" + newArr.length);
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/**
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* 测试结果
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*
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* 数组元素：[1,2,3,4,5,6,7,8,9,10,0,11,12,13,14]
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* 数组长度：15
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*/
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}
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@Test
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public void test_copy_remove() {
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int[] oldArr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
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int index = 2;
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int numMoved = 10 - index - 1;
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System.arraycopy(oldArr, index + 1, oldArr, index, numMoved);
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System.out.println("数组元素：" + JSON.toJSONString(oldArr));
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}
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@Test
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public void init_01() {
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ArrayList<String> list = new ArrayList<String>();
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list.add("aaa");
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list.add("bbb");
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list.add("ccc");
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}
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@Test
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public void init_02() {
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List<String> list = Arrays.asList("aaa", "bbb", "ccc");
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list.add("ddd");
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ArrayList<String> obj = new ArrayList<String>(Arrays.asList("aaa", "bbb", "ccc"));
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}
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@Test
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public void init_03() {
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ArrayList<String> list = new ArrayList<String>() {{
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add("aaa");
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add("bbb");
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add("ccc");
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}};
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}
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@Test
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public void init_04() {
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ArrayList<Integer> list = new ArrayList<Integer>(Collections.nCopies(10, 0));
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}
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@Test
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public void t() {
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List<Integer> list1 = Arrays.asList(1, 2, 3);
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System.out.println("通过数组转换：" + (list1.toArray().getClass() == Object[].class));
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ArrayList<Integer> list2 = new ArrayList<Integer>(Arrays.asList(1, 2, 3));
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System.out.println("通过集合转换：" + (list2.toArray().getClass() == Object[].class));
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}
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@Test
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public void t_hashIdx() {
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List<String> list = new ArrayList<String>(Collections.<String>nCopies(8, "0"));
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list.set("a".hashCode() & 8 - 1, "a");
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list.set("b".hashCode() & 8 - 1, "b");
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list.set("c".hashCode() & 8 - 1, "c");
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list.set("d".hashCode() & 8 - 1, "d");
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list.set("e".hashCode() & 8 - 1, "e");
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list.set("f".hashCode() & 8 - 1, "f");
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list.set("g".hashCode() & 8 - 1, "g");
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System.out.println("元素集合:" + list);
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System.out.println("获取元素f [\"f\".hashCode() & 8 - 1)] Idx：" + ("f".hashCode() & (8 - 1)) + " 元素：" + list.get("f".hashCode() & 8 - 1));
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System.out.println("获取元素e [\"e\".hashCode() & 8 - 1)] Idx：" + ("e".hashCode() & (8 - 1)) + " 元素：" + list.get("e".hashCode() & 8 - 1));
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System.out.println("获取元素d [\"d\".hashCode() & 8 - 1)] Idx：" + ("d".hashCode() & (8 - 1)) + " 元素：" + list.get("d".hashCode() & 8 - 1));
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}
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@Test
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public void t_ensureCapacity01(){
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final int N = 10000000;
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ArrayList<Integer> list = new ArrayList<Integer>();
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long startTime = System.currentTimeMillis();
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for (int i = 0; i < N; i++) {
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list.add(i);
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}
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System.out.println("默认情况耗时："+(System.currentTimeMillis() - startTime));
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}
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@Test
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public void t_ensureCapacity02(){
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final int N = 10000000;
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ArrayList<Integer> list = new ArrayList<Integer>(N);
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long startTime = System.currentTimeMillis();
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for (int i = 0; i < N; i++) {
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list.add(i);
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}
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System.out.println("初始定长容量耗时："+(System.currentTimeMillis() - startTime));
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}
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@Test
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public void t_ensureCapacity03(){
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final int N = 10000000;
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ArrayList<Object> list = new ArrayList<Object>();
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long startTime = System.currentTimeMillis();
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list.ensureCapacity(N);
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for (int i = 0; i < N; i++) {
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list.add(i);
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}
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System.out.println("使用ensureCapacity方法耗时："+(System.currentTimeMillis() - startTime));
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}
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@Test
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public void tt(){
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ArrayList<Object> list = new ArrayList<Object>();
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final int N = 10000000;
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for (int i = 0; i < N; i++) {
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list.add(i);
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}
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ArrayList<Object> list2 = new ArrayList<Object>();
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long startTime1 = System.currentTimeMillis();
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// list2.ensureCapacity(N);
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for (int i = 0; i < N; i++) {
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list2.add(i);
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}
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long endTime1 = System.currentTimeMillis();
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System.out.println("使用ensureCapacity方法后："+(endTime1 - startTime1));
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}
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}

‎pom.xml

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<module>interview-03</module>
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<module>interview-04</module>
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<module>interview-05</module>
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<module>interview-07</module>
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</modules>
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<dependencies>
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<artifactId>fastjson</artifactId>
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<version>1.2.73</version>
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</dependency>
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<!-- https://mvnrepository.com/artifact/junit/junit -->
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.13</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

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