Java基础系列 - JAVA集合ArrayList,Vector，HashMap,HashTable等使用

package com.test4;

import java.util.*;

/**
 * JAVA集合ArrayList,Vector，HashMap,HashTable等使用
 */
public class test4 {
    public static void main(String[] args) {
        //ArrayList异步，线程不安全，性能高  Vector同步，线程安全，性能低
        //定义个ArrayList对象
        ArrayList arrayList = new ArrayList();
        //显示大小
        System.out.println(arrayList.size());
        //添加雇员
        Employer employer1 = new Employer(1000, "张三", 20);
        Employer employer2 = new Employer(1001, "李四", 25);
        Employer employer3 = new Employer(1002, "王五", 30);
        arrayList.add(employer1);
        arrayList.add(employer2);
        arrayList.add(employer3);

        System.out.println("---------foreach循环ArrayList-------------------");
        //iter + tab键快捷键生成foreach代码块
        for (Object item : arrayList) {
            System.out.println("雇员信息：" + item.toString());
        }


        System.out.println("---------for循环ArrayList-------------------");
        //fori 快速生成for代码块
        for (int i = 0; i < arrayList.size(); i++) {
            System.out.println("雇员信息：" + arrayList.get(i).toString());
        }

        System.out.println("---------获取一个雇员信息-------------------");
        //获取一个对象
        Employer employer = (Employer) arrayList.get(0);
        System.out.println("一个雇员信息：" + employer.getName());

        System.out.println("---------显示ArrayList大小-------------------");
        //显示大小
        System.out.println(arrayList.size());

        System.out.println("---------HashMap使用-------------------");
        /**
         * HashMap使用  HashMap异步，线程不安全，性能高 HashTable同步，线程安全，性能低
         */
        Map hm = new HashMap();
        hm.put("1000", employer1);
        hm.put("1001", employer2);
        hm.put("1002", employer3);
        //使用迭代器
        Iterator iter = hm.keySet().iterator();
        while (iter.hasNext()) {
            //取出Key
            String key=iter.next().toString();
            //根据Key取出对象
            Employer emp= (Employer) hm.get(key);
            System.out.println("雇员信息："+emp.toString());
        }


        /**
         * 控制台显示
         0
         ---------foreach循环ArrayList-------------------
         雇员信息：Employer{eid=1000, name='张三', age=20}
         雇员信息：Employer{eid=1001, name='李四', age=25}
         雇员信息：Employer{eid=1002, name='王五', age=30}
         ---------for循环ArrayList-------------------
         雇员信息：Employer{eid=1000, name='张三', age=20}
         雇员信息：Employer{eid=1001, name='李四', age=25}
         雇员信息：Employer{eid=1002, name='王五', age=30}
         ---------获取一个雇员信息-------------------
         一个雇员信息：张三
         ---------显示ArrayList大小-------------------
         3
         ---------HashMap使用-------------------
         雇员信息：Employer{eid=1002, name='王五', age=30}
         雇员信息：Employer{eid=1001, name='李四', age=25}
         雇员信息：Employer{eid=1000, name='张三', age=20}
         */
    }
}


class Employer {
    public Employer(int eid, String name, int age) {
        this.eid = eid;
        this.name = name;
        this.age = age;
    }

    private int eid;
    private String name;
    private int age;

    public int getEid() {
        return eid;
    }

    public void setEid(int eid) {
        this.eid = eid;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Employer{" +
                "eid=" + eid +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

　　

来源：https://www.cnblogs.com/smartsmile/p/11547027.html