Java常用工具——java集合

package com.imooc.set;

import java.util.ArrayList;
import java.util.List;

public class ArrayListDemo {

    public static void main(String[] args) {
        // 用ArrayList存储编程语言的名称，并输出。
        //名称包括”Java”、”C”、”C++“、”Go”和”Swift”
        List list=new ArrayList();
        list.add("Java");
        list.add("C");
        list.add("C++");
        list.add("Go");
        list.add("Swift");
        //输出列表中元素的个数
        System.out.println("列表中元素的个数："+list.size());
        
        //遍历输出所有编程语言
        System.out.println("==========================");
        for(int i=0;i) {
            System.out.print(list.get(i)+" ");
        }
        System.out.println();

        //移除列表中的C++
        System.out.println("==========================");
//        list.remove(2);
        list.remove("C++");
        System.out.println("移除c++后列表的元素为:");
        for(int i=0;i) {
            System.out.print(list.get(i)+" ");
        }
        System.out.println();
    }

}

• 需求

package com.imooc.set;

import java.util.Date;

public class Notice {
    //Notice类，属性：id，title,creator,ctreaterDate
    private int id;
    private String title;
    private String creator;
    private Date creatTime;
    //构造方法
    public Notice(int id, String title, String creator, Date creatTime) {
        super();
        this.id = id;
        this.title = title;
        this.creator = creator;
        this.creatTime = creatTime;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getCreator() {
        return creator;
    }
    public void setCreator(String creator) {
        this.creator = creator;
    }
    public Date getCreatTime() {
        return creatTime;
    }
    public void setCreatTime(Date creatTime) {
        this.creatTime = creatTime;
    }
    
    
    
    
}

package com.imooc.set;

import java.util.ArrayList;
import java.util.Date;


public class NoticeTest {

    public static void main(String[] args) {
        // 创建Notice类的对象，生成三条公告
        Notice notice1=new Notice(1,"欢迎来到java世界！","管理员",new Date());
        Notice notice2=new Notice(2,"请按时提交作业","老师",new Date());
        Notice notice3=new Notice(3,"考勤通知","老师",new Date());
        //添加公告
        ArrayList noticeList=new ArrayList();
        noticeList.add(notice1);
        noticeList.add(notice2);
        noticeList.add(notice3);
        //显示公告
        System.out.println("公告内容为：");
        for(int i=0;i) {
            System.out.println(i+1+":"+((Notice)noticeList.get(i)).getTitle());
        }
    }

}

package com.imooc.set;

import java.util.ArrayList;
import java.util.Date;


public class NoticeTest {
    
    public static void main(String[] args) {
        // 创建Notice类的对象，生成三条公告
        Notice notice1=new Notice(1,"欢迎来到java世界！","管理员",new Date());
        Notice notice2=new Notice(2,"请按时提交作业","老师",new Date());
        Notice notice3=new Notice(3,"考勤通知","老师",new Date());
        //添加公告
        ArrayList noticeList=new ArrayList();
        noticeList.add(notice1);
        noticeList.add(notice2);
        noticeList.add(notice3);
        //显示公告
        System.out.println("公告内容为：");
        for(int i=0;i) {
            System.out.println(i+1+":"+((Notice)noticeList.get(i)).getTitle());
        }
        //再第二条位置新增一条公告
        Notice notice4=new Notice(4,"在线编辑器可以使用了","管理员",new Date());
        noticeList.add(1,notice4);
        //显示公告
        System.out.println("======================");
        System.out.println("公告内容为：");
        for(int i=0;i) {
            System.out.println(i+1+":"+((Notice)noticeList.get(i)).getTitle());
        }
        //删除按时提交作业的公告
        noticeList.remove(2);
        //显示公告
        System.out.println("======================");
        System.out.println("公告内容为：");
        for(int i=0;i) {
            System.out.println(i+1+":"+((Notice)noticeList.get(i)).getTitle());
        }
        //修改第二条公告的title
        notice4.setTitle("JAVA在线编辑器可以使用了！");
        noticeList.set(1,notice4);
        //显示公告
        System.out.println("======================");
        System.out.println("公告内容为：");
        for(int i=0;i) {
            System.out.println(i+1+":"+((Notice)noticeList.get(i)).getTitle());
        }
    }

}