java - 使用比较器对 VO 的嵌套列表进行排序

Question

我正在尝试使用比较器对嵌套 VO 进行排序。我可以使用集合排序来完成此操作，但 intellij 显示警告我们必须使用比较器。但当我们有带有嵌套对象的对象列表时，我无法弄清楚这种用法。

Reports Comparators defined as lambda expressions which could be expressed using methods like Comparator.comparing(). Some comparators like (person1, person2) -> person1.getName().compareTo(person2.getName()) could be simplified like this: Comparator.comparing(Person::getName). Also suggests to replace chain comparisons with Comparator.thenComparing(), e.g. int res = o1.first.compareTo(o2.first); if(res == 0) res = o1.second.compareTo(o2.second); if(res == 0) res = o1.third - o2.third; return res; will be replaced with objs.sort(Comparator.comparing((Obj o) -> o.first).thenComparing(o -> o.second).thenComparingInt(o -> o.third));

这是我的类(class)

public class SortBaseVO {

public SortBaseVO(String prop1, String prop2, String prop3, String prop4, String sortBaseVO2) {
    this.prop1 = prop1;
    this.prop2 = prop2;
    this.prop3 = prop3;
    this.prop4 = prop4;
    this.sortBaseVO2 = sortBaseVO2;
}

private String prop1;

private String prop2;

private String prop3;

private String prop4;

private String sortBaseVO2;

public String getSortBaseVO2() {
    return sortBaseVO2;
}

public void setSortBaseVO2(String sortBaseVO2) {
    this.sortBaseVO2 = sortBaseVO2;
}

public String getProp1() {
    return prop1;
}

public void setProp1(String prop1) {
    this.prop1 = prop1;
}

public String getProp2() {
    return prop2;
}

public void setProp2(String prop2) {
    this.prop2 = prop2;
}

public String getProp3() {
    return prop3;
}

public void setProp3(String prop3) {
    this.prop3 = prop3;
}

public String getProp4() {
    return prop4;
}

public void setProp4(String prop4) {
    this.prop4 = prop4;
}

}

B类

public class SortBaseVO2 {


    private String a;

    private String b;

    private String c;

    private String d;

    public String getA() {
        return a;
    }

    public void setA(String a) {
        this.a = a;
    }

    public String getB() {
        return b;
    }

    public void setB(String b) {
        this.b = b;
    }

    public String getC() {
        return c;
    }

    public void setC(String c) {
        this.c = c;
    }

    public String getD() {
        return d;
    }

    public void setD(String d) {
        this.d = d;
    }

}

当前完成的排序是sortBaseVOList是sortBaseVO的列表

Collections.sort(sortBaseVOList , (sortBaseVO1, sortBaseVO2) ->
        sortBaseVO1.getsortBaseVO2().getB().concat(sortBaseVO1.getsortBaseVO2().getD())
        .compareTo(sortBaseVO2.getsortBaseVO2().getB().concat(sortBaseVO2.getsortBaseVO2().getD()));

我可以更改它以使用比较器吗？

Answer 1

我模拟了你的问题。

我建议使用以下替代方法作为修复此警告的正确方法:

List<SortBaseVO> sortBaseVOList = new ArrayList<>();
Collections.sort(sortBaseVOList , Comparator.comparing(SortBaseVO::getConcat));

在 SortBaseVO 类中，您必须定义以下方法:

public class SortBaseVO {

    // all other methods

    public String getConcat() {
        return getSortBaseVO2().getB().concat(getSortBaseVO2().getD());
    }
}