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);        }    }}