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说明:最近接触到一些js的功能代码，然后发现很多基础都不会弄，
尤其是涉及到数据处理的，java里面常用的数组 ，list ，map，转到js里面，就完全搞不明白，一头雾水，非常影响工作效率，
因此弄了这个小demo，用来记录一下js里面的常用处理数据的一些工具类写法。

js篇
step1: map的基本用法

import {Component, OnInit} from '@angular/core';@Component({selector: 'app-user',standalone: true,imports: [],templateUrl: './user.component.html',styleUrl: './user.component.css'
})
export class UserComponent implements OnInit{constructor() {console.log('constructor')}ngOnInit(): void {console.log('ngOnInit')name.set('a', 1);name.set('b', 2);name.set('c', 3);console.log(name);console.log(name.get('a'));name.set('a', 97);console.log(name.get('a'));console.log(name);console.log(name.size);name.delete('b');console.log(name);console.log(name.size);}}var name = new Map();

step2: js数组的基本用法，相当于java的arraylist，只不过js里面的数组非常的随意，或者叫自由，数组里基本啥都能装，什么乱起八糟的都能往里面塞，也没有固定长度，对于那些写惯了java的人看来，这很离谱

import {Component, OnInit} from '@angular/core';@Component({selector: 'app-user',standalone: true,imports: [],templateUrl: './user.component.html',styleUrl: './user.component.css'
})
export class UserComponent implements OnInit{constructor() {console.log('constructor')}ngOnInit(): void {console.log('ngOnInit')console.log(mycars)console.log(mycars2)var name=mycars2[2];  //获取 修改mycars2[0]="Opel";console.log(name)console.log(mycars2)console.log(apples)console.log(apples2)console.log(apples3)var bannale =  mycars2[3]console.log(bannale)mycars2[4] = "无解"console.log(mycars2)myArray = myArray.filter(item => item !== "banana");console.log(myArray); // ["apple", "orange", "grape"]mycars2 =   myArrayconsole.log(myArray)myArray.push('测试数据')console.log(myArray)}}var mycars = new Array();
mycars[0] = "Saab";
mycars[1] = "Volvo";
mycars[2] = "BMW";var mycars2=new Array("Saab","Volvo","BMW","奥迪");var apples= new Array()var size=10var apples2 = new Array(size)var apples3 = new Array(1,2,3,4)let myArray = ["apple", "banana", "orange", "grape", "bananas", "grape", "bananas"];

=我是分割线====
java篇章
step1: java数组

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;public class Num {public static void main(String[] args) {double[] myList;         // 首选的方法double myList2[];         //  效果相同，但不是首选方法myList = new double[8];double[] arrayRefVar = new double[10];double[] arrayRefVar2 = {1, 2, 3, 4};arrayRefVar[0] = 5.6;arrayRefVar[1] = 4.5;arrayRefVar[2] = 3.3;arrayRefVar[3] = 13.2;arrayRefVar[4] = 4.0;arrayRefVar[5] = 34.33;arrayRefVar[6] = 34.0;arrayRefVar[7] = 45.45;arrayRefVar[8] = 99.993;arrayRefVar[9] = 11123;System.out.println("arrayRefVar数组："+ Arrays.toString(arrayRefVar));System.out.println("arrayRefVar2数组："+Arrays.toString(arrayRefVar2));// 打印所有数组元素for (int i = 0; i < arrayRefVar.length; i++) {System.out.println(arrayRefVar[i] + " ");}// 计算所有元素的总和double total = 0;for (int i = 0; i < arrayRefVar.length; i++) {total += arrayRefVar[i];}System.out.println("数组总和：" + total);// 查找最大元素double max = arrayRefVar[0];for (int i = 1; i < arrayRefVar.length; i++) {if (arrayRefVar[i] > max) {max = arrayRefVar[i];}}System.out.println("最大值为： " + max);}
}

step2: java 使用arraylist

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;public class Lists {public static void main(String[] args) {ArrayList<String> sites = new ArrayList<String>();sites.add("Google");sites.add("Runoob");sites.add("Taobao");sites.add("Weibo");// sites.clear(); 清除所有元素int si = sites.size();String name = sites.get(0);sites.add("韩工");sites.remove(0);System.out.println(name);System.out.println(si);System.out.println(sites);}
}

step3: java 使用hashmap

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;public class Mpas {public static void main(String[] args) {// 创建 HashMap 对象 SitesHashMap<Integer, String> maps = new HashMap<Integer, String>();// 添加键值对maps.put(1, "Google");maps.put(2, "Runoob");maps.put(3, "Taobao");maps.put(4, "Zhihu");// maps.clear(); 清除所有int si = maps.size();String name = maps.get(3);boolean isNum = maps.isEmpty();System.out.println(isNum);System.out.println(name);System.out.println(si);System.out.println(maps);}
}

end