從存放對象的List中去除指定對象

情景如下：

存在一個Bean，該Bean有多個屬性。存在一個List，裏面存放着這些對象，如何去除指定對象(不知道對象index)

問題思考：

• 首先確定不能使用remove()，或者是new一個新的List存放要刪除的對象，然後removeAll()；
• 考慮重寫equals() 和 hashCode();
• 使用迭代器遍歷，但是不能直接remove()；

問題解決代碼如下：

package com.swf.attence.entity;

import com.baomidou.mybatisplus.enums.IdType;

import java.sql.Timestamp;
import java.util.Date;
import com.baomidou.mybatisplus.annotations.TableId;
import com.baomidou.mybatisplus.annotations.TableField;
import com.baomidou.mybatisplus.annotations.TableName;
import java.io.Serializable;
import java.util.Objects;
/**
 * @author white.hou
 * @since 2018-12-30
 */
@TableName("attence_msg")
public class AttenceMsg implements Serializable {

    private static final long serialVersionUID = 1L;


    private Integer id;

    private String userid;
   
    private String checkInTime;
  
    private String cameraidIn;

    private String checkOutTime;
   
    private String cameraidOut;
 
    private Integer checkState;
    
    private Integer failid;

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUserid() {
        return userid;
    }
    public void setUserid(String userid) {
        this.userid = userid;
    }
    public String getCheckInTime() {
        return checkInTime;
    }
    public void setCheckInTime(String checkInTime) {
        this.checkInTime = checkInTime;
    }
    public String getCheckOutTime() {
        return checkOutTime;
    }
    public void setCheckOutTime(String checkOutTime) {
        this.checkOutTime = checkOutTime;
    }
    public Integer getCheckState() {
        return checkState;
    }
    public void setCheckState(Integer checkState) {
        this.checkState = checkState;
    }
    public Integer getFailid() {
        return failid;
    }
    public void setFailid(Integer failid) {
        this.failid = failid;
    }
    public String getCameraidIn() {
        return cameraidIn;
    }
    public void setCameraidIn(String cameraidIn) {
        this.cameraidIn = cameraidIn;
    }
    public String getCameraidOut() {
        return cameraidOut;
    }
    public void setCameraidOut(String cameraidOut) {
        this.cameraidOut = cameraidOut;
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        AttenceMsg that = (AttenceMsg) o;
        return Objects.equals(id, that.id) &&
                Objects.equals(userid, that.userid) &&
                Objects.equals(checkInTime, that.checkInTime) &&
                Objects.equals(cameraidIn, that.cameraidIn) &&
                Objects.equals(checkOutTime, that.checkOutTime) &&
                Objects.equals(cameraidOut, that.cameraidOut) &&
                Objects.equals(checkState, that.checkState) &&
                Objects.equals(failid, that.failid);
    }

    @Override
    public int hashCode() {

        return Objects.hash(id, userid, checkInTime, cameraidIn, checkOutTime, cameraidOut, checkState, failid);
    }

    @Override
    public String toString() {
        return "AttenceMsg{" +
                "id=" + id +
                ", userid='" + userid + '\'' +
                ", checkInTime='" + checkInTime + '\'' +
                ", cameraidIn='" + cameraidIn + '\'' +
                ", checkOutTime='" + checkOutTime + '\'' +
                ", cameraidOut='" + cameraidOut + '\'' +
                ", checkState=" + checkState +
                ", failid=" + failid +
                '}';
    }
}

  /**
    * 使用Mybtis-Plus插件，該List存放的是原來的List，需要從此List中刪除指定對象
    */
  List<UserMsg> userMsgs = selectList(new EntityWrapper<UserMsg>().eq("1", 1));
  /**
    * 此List是尋找指定的對象被userMsgs刪除
    */ 
  List<AttenceMsg> attenceMsgs = attenceMsgMapper.selectList(new EntityWrapper<AttenceMsg>       ().like("check_in_time", day + "%"));
  /**
    * 這個List是用來存放那些需要被刪除的對象
    */ 
  ArrayList<UserMsg> msgs = new ArrayList<>(16);
  for (AttenceMsg a:attenceMsgs
                 ) {
          UserMsg userMsg = selectOne(new EntityWrapper<UserMsg>().eq("userid",     a.getUserid()));
          /**
            * 迭代器遍歷
            */ 
          Iterator<UserMsg> iterator = userMsgs.iterator();
          while (iterator.hasNext()){
             UserMsg next = iterator.next();
              if (next.equals(userMsg)){
                   msgs.add(userMsg);
                 }
           }
                userMsgs.removeAll(msgs);
            }

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