如何在Java中进行合并，相交，差异和反向数据

Question

我想在Java中进行联合，相交，差异和反向操作。首先我有2个实例 ArrayList<Integer>a = [0,2,4,5,6,8,10]b = [5,6,7,8,9,10]联盟b应该返回 c = [0,2,3,4,5,6,7,8,9,10]a相交b应该返回 c = [5,8,10]a偏差b应该返回 c = [0,2,3,4]相反 a = [10,8,6,5,4,2,0]这样的事情。如何在Java中实现该方法？更新：我必须从以下模板开始：package IntSet;import java.util.ArrayList;import java.util.Collection;public class IntSet {private ArrayList<Integer> intset;public IntSet(){    intset = new ArrayList<Integer>();}public void insert(int x){    intset.add(x);}public void remove(int x){    //implement here    intset.indexOf(x);}public boolean member(int x){    //implement here    return true;}public IntSet intersect(IntSet a){    //implement here    return a;}public IntSet union(IntSet a){    //implement here    return a;}public IntSet difference(IntSet a){    //implement here    IntSet b = new IntSet();    return b; }

Answer 1

//Union 

List<Integer> c = new ArrayList<Integer>(a.size() + b.size());

addNoDups(c,a);

addNoDups(c,b);

private void addNoDups(List<Integer> toAddTo,List<Integer> iterateOver) {

    for(Integer num:iterateOver){

        if(toAddTo.indexOf(num) == -1) {

            toAddTo.add(num);

        }

    }

}

//intersection

List<Integer> c = new ArrayList<Integer> (a.size() > b.size() ?a.size():b.size());

c.addAll(a);

c.retainAll(b);

//difference a-b

List<Integer> c = new ArrayList<Integer> (a.size());

c.addAll(a);

c.removeAll(b);

Answer 2

首先，您描述的操作（反向操作除外）是集合操作，而不是列表操作，因此请使用HashSet或（如果需要订购）TreeSet。

    Set<Integer> a = new TreeSet<Integer>(Arrays.asList(new Integer[]{0,2,4,5,6,8,10}));

    Set<Integer> b = new TreeSet<Integer>(Arrays.asList(new Integer[]{5,6,7,8,9,10}));

    //union

    Set<Integer> c = new TreeSet<Integer>(a);

    c.addAll(b);

    System.out.println(c);

    //intersection

    Set<Integer> d = new TreeSet<Integer>(a);

    d.retainAll(b);

    System.out.println(d);

    //difference

    Set<Integer> e = new TreeSet<Integer>(a);

    e.removeAll(b);

    System.out.println(e);

    //reverse

    List<Integer> list = new ArrayList<Integer>(a);

    java.util.Collections.reverse(list);

    System.out.println(list);