java 比较器按多个字段排序

Question

需要按 3 个字符串字段对 class 目录进行排序。第一个：按1个值排序-s1；然后按字符串长度排序——s1+s2+s3；按 2 值排序后 - s2; 并按 3 个值排序 - s3。在我的代码中，它适用于值 1 和字符串长度排序，但按 2 值排序不起作用。我如何按多个值对 class 目录进行排序？ Class 目录：

    public class Dir {

    private String s1 = "";
    private String s2 = "";
    private String s3 = "";

    public Dir(String s1){
        this.s1 = s1;
    }

    public Dir(String s1, String s2){
        this.s1 = s1;
        this.s2 = s2;
    }

    public Dir(String s1, String s2, String s3){
        this.s1 = s1;
        this.s2 = s2;
        this.s3 = s3;
    }

    public String getS1() {
        return s1;
    }

    public void setS1(String s1) {
        this.s1 = s1;
    }

    public String getS2() {
        return s2;
    }

    public void setS2(String s2) {
        this.s2 = s2;
    }

    public String getS3() {
        return s3;
    }

    public void setS3(String s3) {
        this.s3 = s3;
    }

    @Override
    public String toString() {
        return s1 + "\" + s2 +"\"+ s3 ;
    }
}





    //Comparator for 2 value:
    public class DirReversComparatorS2 implements Comparator<Dir> {
    @Override
    public int compare(Dir o1, Dir o2) {

        if ((o1.getS2().compareTo(o2.getS2())) > 0) {
            return -1;
        }
        else if ((o1.getS2().compareTo(o2.getS2())) < 0) {
            return 1;
        }
        else {
            return 0;
        }
    }
}

//Comparator for 3 value
public class DirReversComparatorS3 implements Comparator<Dir> {
@Override
public int compare(Dir o1, Dir o2) {


    if ((o1.getS3().compareTo(o2.getS3())) > 0) {
        return -1;
    } else if ((o1.getS3().compareTo(o2.getS3())) < 0) {
        return 1;
    }
    else {
        return 0;
    }
}

}

//Comparator for string lenght:

public class DirReversStringComparator implements Comparator<Dir> {
@Override
public int compare(Dir o1, Dir o2) {
    if (o1.toString().length() > o2.toString().length()) {
        return 1;
    }
    else {
        return -1;
    }

}

}

    //Main class:
    public class Main {
    public static void main(String[] args){

        Comparator<Dir> dcomp = new DirComparatorS1().thenComparing(new DirComparatorS2(
        ).thenComparing(new DirComparatorS3()));
        TreeSet<Dir> dir = new TreeSet<>(dcomp);
        dir.add(new Dir("K1"));
        dir.add(new Dir("K1","SK2"));
        dir.add(new Dir("K1","SK1","SSK2"));
        dir.add(new Dir("K1", "SK1", "SSK1"));
        dir.add(new Dir("K2"));
        dir.add(new Dir("K2", "SK2", "SSK1"));
        dir.add(new Dir("K2", "SK2", "SSK2"));
        dir.add(new Dir("K2", "SK3", "SSK2"));
        dir.add(new Dir("K2", "SK2", "SSK3"));



        System.out.println("Отсортирован по возрастанию");
        for(Dir d : dir){
            System.out.println(d.getS1()+"\"+d.getS2()+"\"+d.getS3());
        }


        //This code does not works!
        Comparator<Dir> reverse = new DirReversComparatorS1().thenComparing(
                new DirReversStringComparator()).thenComparing(
                        new DirReversComparatorS2()).thenComparing(
                                new DirReversComparatorS3());


        TreeSet<Dir> rdir = new TreeSet<>(reverse);
        rdir.add(new Dir("K1"));
        rdir.add(new Dir("K1","SK2"));
        rdir.add(new Dir("K2","SK2"));
        rdir.add(new Dir("K1","SK1","SSK2"));
        rdir.add(new Dir("K1", "SK1", "SSK1"));
        rdir.add(new Dir("K1", "SK1", "SSK2"));
        rdir.add(new Dir("K2"));
        rdir.add(new Dir("K2", "SK4", "SSK3"));
        rdir.add(new Dir("K2", "SK2", "SSK5"));
        rdir.add(new Dir("K2","SK1"));
        rdir.add(new Dir("K2", "SK2", "SSK1"));
        rdir.add(new Dir("K1", "SK1"));
        rdir.add(new Dir("K2", "SK2", "SSK2"));
        rdir.add(new Dir("K1", "SK2"));
        rdir.add(new Dir("K2", "SK3", "SSK2"));
        rdir.add(new Dir("K2", "SK2", "SSK3"));
        rdir.add(new Dir("K2", "SK2", "SSK5"));
        rdir.add(new Dir("K2", "SK1", "SSK3"));
        rdir.add(new Dir("K1", "SK3"));
        rdir.add(new Dir("K1", "SK3", "SSK1"));


        System.out.println("Отсортирован по убыванию");
        for(Dir d : rdir){
            System.out.println(d.getS1()+"\"+d.getS2()+"\"+d.getS3());
        }
    }
}

解决方法是什么？谢谢！

Answer 1

像这样：

dirs
   .sort(Comparator.comparing(Dir::getS1)
                    .thenComparingInt(
                            d -> d.getS1().length() + d.getS2().length() + d.getS3().length())
                    .thenComparing(Dir::getS2)
                    .thenComparing(Dir::getS3));

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