java - 具有交集和并集的链表

Question

我有两个列表，都添加了整数。我想将两个列表相交并并集。我有我的代码，但由于某种原因它无法编译。

关于为什么我不能简单地 LinkedList.intersection(argument, argument) 有什么建议吗？

import java.util.HashSet;
import java.util.LinkedList;
import java.util.Set;

public class IntegerSet 
{


    public static void main(String args[]) {


        LinkedList<Double> list1 = new LinkedList<Double>();
        list1.add((double) 5);
        list1.add((double) 15);
        list1.add((double) 3);
        list1.add((double) 15);


        LinkedList<Double> list2 = new LinkedList<Double>();
        list2.add((double) 15);
        list2.add((double) 8);
        list2.add((double) 16);
        list2.add((double) 11);

        // Calculating Intersection of two Set in Java
        LinkedList<Double> intersection = LinkedList.intersection(list1, list2);
        System.out.printf("Intersection of two Set %s and %s in Java is %s %n",
                list1.toString(), list2.toString(), intersection.toString());
        System.err.println("Number of elements common in two Set : "
                           + intersection.size());

        // Calculating Union of two Set in Java
        LinkedList<Double> union = LinkedList.union(list1, list2);
        System.out.printf("Union of two Set %s and %s in Java is %s %n",
                list1.toString(), list2.toString(), union.toString());
        System.out.println("total number of element in union of two Set is : "
                            + union.size());
    }

}

Answer 1

除此之外，尝试在链接列表上使用intersection和union方法是您可以做的最糟糕的事情之一复杂性方面。另外，

// Calculating Union of two Set in Java
LinkedList<Double> union = LinkedList.union(list1, list2);

Set 与 List 不同。此外，这存在于 API 中。 :

col.retainAll(otherCol) // for intersection
col.addAll(otherCol) // for union

另请参阅这篇文章:Intersection and union of ArrayLists in Java

第三方库:Apache Commons CollectionUtils