Contains方法，查看序列中是否包含某个元素

Equals方法重写

package com.imooc.collection;
/** * 课程类 * @author Monica * */
public class Course {
    
    public String id;
    public String name;
    public Course(String id,String name){
        this.id = id;
        this.name = name;
    }
    public Course(){

    }
    @Override
    public boolean equals(Object obj){
        if(this == obj){
   //通过双等号判断对象相等
            return true;
        }
        if(obj == null)//如果obj等于空
            return false;
        if(!(obj instanceof Course))//ogj对象不是Course类型
                return false;
        //前面都通过了
        Course course = (Course)obj;//强转为course对象
        if(this.name == null){
   //通过名称判断是否为course对象，判断名称是否为空
            if(course.name == null)//强转为course的对象是否为空，两个都为空，是相等的
                return true;
            else
                return false;
        }else{
   //当前的对象不为空
            if(this.name.equals(course.name))//判断name是否相等
                return true;
            else//name不相等
                return false;
        }
    }
}

package com.imooc.collection;

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

public class SetTest {
    public List<Course> coursesToSelect;

    private Scanner console;

    public SetTest(){
        coursesToSelect = new ArrayList<Course>();
        console = new Scanner(System.in);
    }
    /** * 用于往coursesToSelect中添加备选课程 */
    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 cr1 = new Course("1","数据结构");
        coursesToSelect.add(cr1);
        //取出元素  get方法
        Course temp = (Course)coursesToSelect.get(0);
        //System.out.println("添加了课程："+temp.id+":"+temp.name);

        Course cr2 = new Course("2","C语言");//提供索引位置，插入元素
        coursesToSelect.add(0, cr2);
        Course temp2 = (Course)coursesToSelect.get(0);
        //System.out.println("添加了课程："+temp2.id+":"+temp2.name);

        coursesToSelect.add(cr1);
        //取出元素  get方法
        Course temp0 = (Course)coursesToSelect.get(2);
        //System.out.println("添加了课程："+temp.id+":"+temp.name);

        //以下方法会抛出数组下标越界异常
        //Course cr3 = new Course("3","Test");
        //coursesToSelect.add(4,cr3);数组越界

        Course[] course = {new Course("3","离散数学"),new Course("4","汇编语言")};
        coursesToSelect.addAll(Arrays.asList(course));
        Course temp3 = (Course)coursesToSelect.get(3);
        Course temp4 = (Course)coursesToSelect.get(4);

        //System.out.println("添加了两门课程："+temp3.id+":"+temp3.name+";"+temp4.id+":"+temp4.name);

        Course[] course2 = {new Course("5","高等数学"),new Course("6","大学英语")};
        coursesToSelect.addAll(2,Arrays.asList(course2));
        Course temp5 = (Course)coursesToSelect.get(2);
        Course temp6 = (Course)coursesToSelect.get(3);

        //System.out.println("添加了两门课程："+temp5.id+":"+temp5.name+";"+temp6.id+":"+temp6.name);

    }
    /** * 通过for each方法访问集合元素 * @param args */
    public void testForEach(){
        System.out.println("有如下课程待选（通过for each访问）：");
        for(Object obj:coursesToSelect){
            Course cr = (Course)obj;
            System.out.println("课程："+cr.id+":"+cr.name);
        }
    }
    /** * 测试List的contains方法 * containsAll方法，是否包含多个元素 * @param args */
    public void testListContains(){
        //取得备选课程序列的第0个元素
        Course course = coursesToSelect.get(0);
        //打印输出courseToSelected是否包含course对象
        System.out.println("取得课程："+course.name);
        System.out.println("备选课程中是否包含课程："+course.name+","+coursesToSelect.contains(course));
        //提示输入课程名称
        System.out.println("请输入课程名称：");
        String name = console.next();
        //创建一个新的课程对象，ID和名称，与course对象完全一样
        Course course2 = new Course();
        course2.name = name;
        System.out.println("新创建课程："+course2.name);
        System.out.println("备选课程中是否包含课程："+course2.name+","+coursesToSelect.contains(course2));

    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        SetTest st = new SetTest();
        st.testAdd();
        st.testListContains();
        /*st.testForEach(); //创建一个学生对象 Student student = new Student("1","小王"); System.out.println("欢迎学生："+student.name+"选课！"); //创建要给Scanner对象，用来接收从键盘输入的课程ID Scanner console = new Scanner(System.in); for(int i=0;i<3;i++){ System.out.println("请输入课程ID"); String courseId = console.next(); for(Course cr:st.coursesToSelect){ if(cr.id.equals(courseId)){ student.courses.add(cr); *//** * Set中，添加某个对象，无论添加多少次 * 最终只会保留一个该对象(的引用）, * 并且，保留第一次添加的那一个 *//* //student.courses.add(cr); //student.courses.add(null); } } } st.testForEachForSet(student);*/
    }
    public void testForEachForSet(Student student){
        //打印输出，学生所选的课程！
        System.out.println("供选择了："+student.courses.size());
        for(Course cr:student.courses){
            System.out.println("选择了课程："+cr.id+":"+cr.name);
        }
    }

}