java - 比较树集是否相等

Question

我有两套HashSet我转换为 TreeSet对其进行排序以便于比较。转换后HashSet至TreeSet 。当我使用“等于”函数比较这两个 TreeSet 时，它说它们是不同的。我调试它，但它以相同的顺序显示相同的内容。我不明白出了什么问题？

   public class TestProductBundle {
    @SuppressWarnings("unused")
    public static void main(String args[]) {

        // HashSet
        Set<ClassA> hashSetA = new HashSet<ClassA>() {
            {
                add(new ClassA("name", 1, "desc"));
                add(new ClassA("name", 2, "desc"));
                add(new ClassA("name", 3, "desc"));
            }
        };

        Set<ClassA> hashSetB = new HashSet<ClassA>() {
            {
                add(new ClassA("name", 1, "desc"));
                add(new ClassA("name", 2, "desc"));
                add(new ClassA("name", 3, "desc"));
            }
        };

        TreeSet<ClassA> treeSetA = new TreeSet<ClassA>(new CompareID()) {
            {
                addAll(hashSetA);
            }
        };

        TreeSet<ClassA> treeSetB = new TreeSet<ClassA>(new CompareID()) {
            {
                addAll(hashSetB);
            }
        };

        if (treeSetA.equals(treeSetB))
            System.out.println("Equal set of tree");
        else
            System.out.println("Unequal set of tree");   // this is result.
    }}

A 类给出如下:

class ClassA {
String name;
int id;
String desc;

public ClassA(String name, int id, String desc) {
    this.name = name;
    this.id = id;
    this.desc = desc;
}

    int getId() {
        return id;
    }
}

class CompareID implements Comparator<ClassA> {
    @Override
    public int compare(ClassA o1, ClassA o2) {
        if (o1.getId() > o2.getId())
            return 1;
        else
            return -1;
    }
}

编辑: 我试过if (treeSetA.containsAll(treeSetB) && treeSetB.containsAll(treeSetA)此条件也。但结果相同，"Unequal set of tree"

Answer 1

您的 compare 方法始终返回不等式。

来自文档:

[...]

a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

[..]

public int compare(ClassA o1, ClassA o2) {
    if (o1.getId() > o2.getId())
        return 1;
    else if(o2.getId() > o1.getId())
        return -1;
    // 0  indicates equality.
    else return 0;
}

在输出中包含此结果

Equal set of tree