經過Guava實現兩個包含不一樣對象的List合併成一個List

1.目的

以前的項目中有個需求，要求不可使用多表聯查，分別查詢多張表的數據，再經過兩張表的關聯id將查詢出的兩個list數據合併成一個list 若是有兩個List，List< A>、List< B >， 其中，A的主鍵爲B的外鍵，如今要將他們合併成一個列表List<Map<A.id,B>>。

2.首先先導入guava依賴包

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>18.0</version>
</dependency>
複製代碼

3.demo代碼

import com.google.common.base.Function;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

import java.util.List;
import java.util.Map;

public class ListUtil {
    public static void main(String[] args) {
        Aoo a = new Aoo(11, "a1", "123");
        Aoo a2 = new Aoo(22, "a2", "12345");
        Aoo a3 = new Aoo(23, "a2222", "1234522");
        Aoo a4 = new Aoo(24, "a2", "12345");
        Aoo a5 = new Aoo(25, "a2", "12345");

        Boo b = new Boo(1, 11, "b1", "demo");
        Boo b2 = new Boo(2, 22, "b2", "demo2");
        Boo b3 = new Boo(3, 23, "b3", "demo3");
        List<Aoo> aooList = Lists.newArrayList(a, a2, a3, a4, a5);
        List<Boo> booList = Lists.newArrayList(b, b2, b3);
        List<AooVO> result = Lists.newArrayList();
        //先將booList轉成以aooId爲key，boo爲value的map
        Map<Integer, Boo> booMap = Maps.uniqueIndex(booList, new Function<Boo, Integer>() {
            @Override
            public Integer apply(Boo boo) {
                return boo.getAooId();
            }
        });
        //經過aooId從booMap獲取boo對象，再拼接爲最後須要的VO對象
        for (Aoo aoo : aooList) {
            Boo boo = booMap.get(aoo.getId());
            if (boo != null) {
                AooVO aooVO = new AooVO();
                aooVO.setId(aoo.getId());
                aooVO.setName(aoo.getName());
                aooVO.setValue(aoo.getValue());
                aooVO.setType(boo.getType());
                aooVO.setbName(boo.getName());
                result.add(aooVO);
            }
        }
        System.out.println(result);
        //經過aooId排序
        Collections.sort(result, new Comparator<AooVO>() {
            @Override
            public int compare(AooVO o1, AooVO o2) {
                return o2.getId()-o1.getId();
            }
        });
        System.out.println(result);
    }
}

class Aoo {
    private Integer id;
    private String name;
    private String value;

    public Aoo(Integer id, String name, String value) {
        this.id = id;
        this.name = name;
        this.value = value;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Aoo{" +
                "id=" + id +
                ", name='" + name + '\'' + ", value='" + value + '\'' + '}'; } } class Boo { private Integer id; private Integer aooId; private String name; private String type; public Boo(Integer id, Integer aooId, String name, String type) { this.id = id; this.aooId = aooId; this.name = name; this.type = type; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public Integer getAooId() { return aooId; } public void setAooId(Integer aooId) { this.aooId = aooId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getType() { return type; } public void setType(String type) { this.type = type; } @Override public String toString() { return "Boo{" + "id=" + id + ", aooId=" + aooId + ", name='" + name + '\'' +
                ", type='" + type + '\'' + '}'; } } class AooVO { private Integer id; private String name; private String bName; private String value; private String type; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getbName() { return bName; } public void setbName(String bName) { this.bName = bName; } public String getValue() { return value; } public void setValue(String value) { this.value = value; } public String getType() { return type; } public void setType(String type) { this.type = type; } @Override public String toString() { return "AooVO{" + "id=" + id + ", name='" + name + '\'' + ", bName='" + bName + '\'' +
                ", value='" + value + '\'' + ", type='" + type + '\'' + '}'; } } 複製代碼