LinkedHashSet的HashSet不会删除具有多个元素的LinkedHashSet(HashSet of LinkedHashSets does not delete LinkedHashSet with multiple elements)

 我正在学习数据结构和算法，并试图在Java中实现不相交的数据结构。 这是我的代码做同样的事情 - 
 
import java.util.*;

public class DisjointSet<T> {
    Set<LinkedHashSet<T>> allSets;

    DisjointSet()   {
        allSets = new HashSet<LinkedHashSet<T>>();
    }

    public void makeSet(T t)    {
        Iterator itr = allSets.iterator();
        while (itr.hasNext())   {
            LinkedHashSet set = (LinkedHashSet) itr.next();
            if (set.contains(t))    {
                return;
            }
        }

        LinkedHashSet<T> set = new LinkedHashSet<T>();
        set.add(t);

        allSets.add(set);
    }

    public T findSet(T t)   {       
        Iterator itr = allSets.iterator();
        while (itr.hasNext())   {
            LinkedHashSet set = (LinkedHashSet) itr.next();
            if (set.contains(t))    {
                Iterator itr1 = set.iterator();
                T t1 = (T) itr1.next();
                return t1;
            }
        }

        return null;
    }

    public void union(T t1, T t2)   {
        LinkedHashSet<T> set1 = null, set2 = null;

        Iterator itr = allSets.iterator();
        while (itr.hasNext())   {
            LinkedHashSet set = (LinkedHashSet) itr.next();
            if (set.contains(t1))   {
                set1 = (LinkedHashSet<T>) set;
                System.out.println("Got set1:: " + set1);
            } else if (set.contains(t2))    {
                set2 = (LinkedHashSet<T>) set;
                System.out.println("Got set2:: " + set2);
            }
        }

        if (null != set1)   {
            System.out.println("Adding set2 to set1");
            set1.addAll(set2);

            if (null != set2)   {
                System.out.println("Removing set2");
                System.out.println(allSets.remove(set2));
            }
        }
    }

    public void viewAllSets()   {
        System.out.println(this.allSets);
    }
}
 
 这是我正在运行的代码来测试我的实现 - 
 
public class DisjointTest   {   
    public static void main(String [] args) {
        DisjointSet<Integer> dsets = new DisjointSet<Integer>();

        dsets.makeSet(30);
        dsets.makeSet(600);
        dsets.makeSet(20);
        dsets.makeSet(25);
        dsets.makeSet(90);
        dsets.makeSet(100);
        dsets.makeSet(1);

        dsets.viewAllSets();
        System.out.println();

        System.out.println(dsets.findSet(25));

        dsets.union(20, 25);
        dsets.viewAllSets();

        System.out.println();

        System.out.println(dsets.findSet(25));

        dsets.union(1, 100);
        dsets.viewAllSets();

        System.out.println();

        dsets.union(20, 100);
        dsets.viewAllSets();

        System.out.println(dsets.findSet(100));

        System.out.println();

        dsets.union(30, 90);
        dsets.viewAllSets();

        System.out.println();

        dsets.union(1, 90);
        dsets.viewAllSets();
    }   
}
 
 当我尝试将一个集合与另一个集合，比如说set2，它有2个或更多元素时，集合会正确合并，但即使在调用allsets.remove(set2)之后，set2也不会从集合集合中删除 
 
 但是，如果要合并的集合，即; set2只有1个元素， allSets.remove(set2)成功地从集合集合中删除了set2。 
 
 以下是我的代码输出，证实了我的问题 - 
 
[[1], [100], [20], [25], [600], [90], [30]]

25
Got set1:: [20]
Got set2:: [25]
Adding set2 to set1
Removing set2
true
[[1], [100], [20, 25], [600], [90], [30]]

20
Got set1:: [1]
Got set2:: [100]
Adding set2 to set1
Removing set2
true
[[1, 100], [20, 25], [600], [90], [30]]

Got set2:: [1, 100]
Got set1:: [20, 25]
Adding set2 to set1
Removing set2
false
[[1, 100], [20, 25, 1, 100], [600], [90], [30]]
1

Got set1:: [20, 25, 1, 100]
Got set2:: [90]
Adding set2 to set1
Removing set2
true
[[1, 100], [20, 25, 1, 100, 90], [600], [30]]
 
 我无法理解为什么HashSet.remove(LinkedHashSet)无法删除具有多个元素的LinkedHashSet ，但成功删除了包含1个元素的LinkedHashSet 。 
 
 任何帮助将受到高度赞赏。 非常感谢你。 

I am learning Data Strucrtures and Algorithms, and trying to implement disjoint-set data structure in Java. Here is my code to do the same-
 
import java.util.*;

public class DisjointSet<T> {
    Set<LinkedHashSet<T>> allSets;

    DisjointSet()   {
        allSets = new HashSet<LinkedHashSet<T>>();
    }

    public void makeSet(T t)    {
        Iterator itr = allSets.iterator();
        while (itr.hasNext())   {
            LinkedHashSet set = (LinkedHashSet) itr.next();
            if (set.contains(t))    {
                return;
            }
        }

        LinkedHashSet<T> set = new LinkedHashSet<T>();
        set.add(t);

        allSets.add(set);
    }

    public T findSet(T t)   {       
        Iterator itr = allSets.iterator();
        while (itr.hasNext())   {
            LinkedHashSet set = (LinkedHashSet) itr.next();
            if (set.contains(t))    {
                Iterator itr1 = set.iterator();
                T t1 = (T) itr1.next();
                return t1;
            }
        }

        return null;
    }

    public void union(T t1, T t2)   {
        LinkedHashSet<T> set1 = null, set2 = null;

        Iterator itr = allSets.iterator();
        while (itr.hasNext())   {
            LinkedHashSet set = (LinkedHashSet) itr.next();
            if (set.contains(t1))   {
                set1 = (LinkedHashSet<T>) set;
                System.out.println("Got set1:: " + set1);
            } else if (set.contains(t2))    {
                set2 = (LinkedHashSet<T>) set;
                System.out.println("Got set2:: " + set2);
            }
        }

        if (null != set1)   {
            System.out.println("Adding set2 to set1");
            set1.addAll(set2);

            if (null != set2)   {
                System.out.println("Removing set2");
                System.out.println(allSets.remove(set2));
            }
        }
    }

    public void viewAllSets()   {
        System.out.println(this.allSets);
    }
}
 
And here is the code I am running to test my implementation-
 
public class DisjointTest   {   
    public static void main(String [] args) {
        DisjointSet<Integer> dsets = new DisjointSet<Integer>();

        dsets.makeSet(30);
        dsets.makeSet(600);
        dsets.makeSet(20);
        dsets.makeSet(25);
        dsets.makeSet(90);
        dsets.makeSet(100);
        dsets.makeSet(1);

        dsets.viewAllSets();
        System.out.println();

        System.out.println(dsets.findSet(25));

        dsets.union(20, 25);
        dsets.viewAllSets();

        System.out.println();

        System.out.println(dsets.findSet(25));

        dsets.union(1, 100);
        dsets.viewAllSets();

        System.out.println();

        dsets.union(20, 100);
        dsets.viewAllSets();

        System.out.println(dsets.findSet(100));

        System.out.println();

        dsets.union(30, 90);
        dsets.viewAllSets();

        System.out.println();

        dsets.union(1, 90);
        dsets.viewAllSets();
    }   
}
 
When I try to merge a set with anther one, say set2, which has 2 or more elements, the sets get merged properly but set2 is not removed from the collection of sets even after calling allsets.remove(set2)
 
But, if the set to be merged, i.e; set2, has only 1 elements, allSets.remove(set2) successfully removes set2 from the collection of sets.
 
Here is the output of my code which confirms my problem-
 
[[1], [100], [20], [25], [600], [90], [30]]

25
Got set1:: [20]
Got set2:: [25]
Adding set2 to set1
Removing set2
true
[[1], [100], [20, 25], [600], [90], [30]]

20
Got set1:: [1]
Got set2:: [100]
Adding set2 to set1
Removing set2
true
[[1, 100], [20, 25], [600], [90], [30]]

Got set2:: [1, 100]
Got set1:: [20, 25]
Adding set2 to set1
Removing set2
false
[[1, 100], [20, 25, 1, 100], [600], [90], [30]]
1

Got set1:: [20, 25, 1, 100]
Got set2:: [90]
Adding set2 to set1
Removing set2
true
[[1, 100], [20, 25, 1, 100, 90], [600], [30]]
 
I am not able to comprehend why HashSet.remove(LinkedHashSet) is not able to remove a LinkedHashSet with multiple elements, but successfully removes a LinkedHashSet with 1 element.
 
Any help will be highly appreciated. Thank you very much.

原文：https://stackoverflow.com/questions/34454406