集合例子：学生选课

Posted 2020-10-23 sunshine_96

利用集合存储课程信息：

1.Course类

package com.collection;

public class Course {
    public String id;
    public String name;
    public Course(String id,String name)
    {
        this.id=id;
        this.name=name;
    }

}

2.ListTest类

package com.collection;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;


/**
 * 备选课程类
*/

public class ListTest {
    //List用于存放备选课程
    public List CourseToSelect;
    public ListTest(){
        this.CourseToSelect = new ArrayList();
    }
    //用于往CourseToSelect添加备选课程
    public void TestAdd(){
        //创建一个课程对象，并通过调用add方法，添加到备选课程List中
        Course c1 = new Course("1","数据结构");
        CourseToSelect.add(c1);
        Course temp = (Course) CourseToSelect.get(0);
        System.out.println("添加了课程:"+temp.id+"_"+temp.name);
        
        
        Course c2 = new Course("2","c语言");
        CourseToSelect.add(0, c2);
        Course temp2 = (Course) CourseToSelect.get(0);
        System.out.println("添加了课程:"+temp2.id+"_"+temp2.name);
        
        Course[] course = {new Course("3","离散数学"),new Course("4","汇编语言")};
        CourseToSelect.addAll(Arrays.asList(course));
        Course temp3 = (Course) CourseToSelect.get(2);
        Course temp4 = (Course) CourseToSelect.get(3);
        System.out.println("添加了两门课程:"+temp3.id+"_"+temp3.name+";"+temp4.id+"_"+temp4.name);
        
        CourseToSelect.add(c1);
        Course temp0 = (Course) CourseToSelect.get(0);
        System.out.println("添加了课程:"+temp0.id+"_"+temp0.name);
        
        Course[] course2 = {new Course("5","高等数学"),new Course("6","大学英语")};
        CourseToSelect.addAll(2, Arrays.asList(course2));
        Course temp5 = (Course) CourseToSelect.get(2);
        Course temp6 = (Course) CourseToSelect.get(3);
        System.out.println("添加了两门课程:"+temp5.id+"_"+temp5.name+";"+temp6.id+"_"+temp6.name);
        
    }
    //取得List中元素的方法
    public void testGet(){
        int size = CourseToSelect.size();
        System.out.println("有如下课程待选：");
        for(int i = 0;i<size;i++)
        {
            Course cr = (Course) CourseToSelect.get(i);
            System.out.println("课程："+cr.id+":"+cr.name);
        }
    }
    //通过迭代器遍历List中的元素
    public void testIterator(){
        //通过集合的iterator方法，取得迭代器的实例；
        Iterator it = CourseToSelect.iterator();
        System.out.println("有如下课程待选(通过迭代器取得)：");
        while(it.hasNext()){
            Course cr2 = (Course) it.next(); 
            System.out.println("课程："+cr2.id+":"+cr2.name);
        }
    
    } 
    //通过for each遍历list中的元素
    public void testForEach(){
        System.out.println("有如下课程待选(通过for each取得)：");
        for(Object obj:CourseToSelect){
            Course cr = (Course) obj;
            System.out.println("课程："+cr.id+":"+cr.name);
            
        }
            
    }
    
    //修改List中的元素
    public void testModify(){
        CourseToSelect.set(6, new Course("7","毛概"));
        
    }
    
    //删除List中的元素
    public void testRemove(){
        /*Course cr = (Course) CourseToSelect.get(6);
        System.out.println("课程："+cr.id+":"+cr.name+"我即将被删除");
        CourseToSelect.remove(cr);  //删除具体的元素*/
        //CourseToSelect.remove(4);  //删除索引4位置上的元素
        Course[] courses = {(Course)CourseToSelect.get(4),(Course)CourseToSelect.get(5)};
        CourseToSelect.removeAll(Arrays.asList(courses));
        System.out.println("成功被删除");
        testForEach();
    }
    
    public static void main(String[] args){
        ListTest lt = new ListTest();
        lt.TestAdd();
        lt.testGet();
        lt.testIterator();
        lt.testForEach();
        lt.testModify();
        lt.testForEach();
        lt.testRemove();
    }

}