比较两集合获取异同

原理：利用HashMap<Key,Value>,put\get方法底层（hash碰撞），故需重写对象的equals（），hashCode（）方法！

集合中实例

package io.unify.cva.entity;

import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;

import java.io.Serializable;
import java.util.Objects;

/**
 * 
 *
 * @author chenjunhua [email protected]
 * @since 1.0.0 2019-06-10
 */
@TableName("cva_contact_info")
public class CvaContactInfoEntity implements Serializable {
	private static final long serialVersionUID = 1L;

	/**
	 * id
	 */
	@TableId
	private Long id;

    /**
     * 电话号码
     */
	private String telephoneNumber;
    /**
     * 姓名
     */
	private String name;
    /**
     * 通付盾设备(Imei)号
     */
	private String imeiCode;

	public Long getId() {
		return id;
	}

	public void setId(Long id) {
		this.id = id;
	}
	public void setTelephoneNumber(String telephoneNumber) {
		this.telephoneNumber = telephoneNumber;
	}
	public String getTelephoneNumber() {
		return telephoneNumber;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getName() {
		return name;
	}
	public void setImeiCode(String imeiCode) {
		this.imeiCode = imeiCode;
	}
	public String getImeiCode() {
		return imeiCode;
	}

	@Override
	public boolean equals(Object obj) {
		if(obj == this) {return true;}
		if (!(obj instanceof CvaContactInfoEntity)) { return false;}
		CvaContactInfoEntity re = (CvaContactInfoEntity) obj;
		return telephoneNumber.equals(re.getTelephoneNumber())&&
				name.equals(re.getName())&&
				imeiCode.equals(re.getImeiCode());
	}
	@Override
	public int hashCode() {
		return Objects.hash(telephoneNumber, name, imeiCode);
	}
}

 工具类：

/**
     * @description: 比较两个list，取出存在newList中，但不存在dbList中的数据，差异数据放入differentList
     * @param  newList
     * @param  dbList
     * @return List
     * @throws
     * @author chenjunhua
     * @date 2019/6/12 15:25
     */
    public static <T> List<T> getDifferentList(List<T> newList, List<T> dbList) {
        Map<T,Integer> map = new HashMap<T,Integer>(dbList.size());
        List<T> differentList = new ArrayList<T>();
        for(T resource : dbList){
            map.put(resource,1);
        }
        for(T resource1 : newList){
            if(map.get(resource1)==null){
                differentList.add(resource1);
            }
        }
        return differentList;
    }