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import java.util.*;

import java.util.stream.Collectors;

public class ListComparison {

public static void main(String[] args) {

// 创建两个示例List

List<String> list1 = Arrays.asList("apple", "banana", "orange", "grape", "kiwi");

List<String> list2 = Arrays.asList("banana", "grape", "mango", "pear");

System.out.println("List1: " + list1);

System.out.println("List2: " + list2);

System.out.println();

// 方法1: 使用Stream API (推荐)

System.out.println("=== 使用Stream API ===");

// 交集 (两个List都包含的元素)

List<String> intersection = list1.stream()

.filter(list2::contains)

.collect(Collectors.toList());

System.out.println("交集: " + intersection);

// 差集 (在list1中但不在list2中的元素)

List<String> difference1 = list1.stream()

.filter(item -> !list2.contains(item))

.collect(Collectors.toList());

System.out.println("List1 - List2 (差集): " + difference1);

// 差集 (在list2中但不在list1中的元素)

List<String> difference2 = list2.stream()

.filter(item -> !list1.contains(item))

.collect(Collectors.toList());

System.out.println("List2 - List1 (差集): " + difference2);

// 对称差集 (两个List的并集减去交集)

List<String> symmetricDifference = new ArrayList<>();

symmetricDifference.addAll(difference1);

symmetricDifference.addAll(difference2);

System.out.println("对称差集: " + symmetricDifference);

System.out.println();

// 方法2: 使用Collection方法

System.out.println("=== 使用Collection方法 ===");

// 交集

List<String> intersection2 = new ArrayList<>(list1);

intersection2.retainAll(list2);

System.out.println("交集: " + intersection2);

// 差集

List<String> difference1_2 = new ArrayList<>(list1);

difference1_2.removeAll(list2);

System.out.println("List1 - List2 (差集): " + difference1_2);

List<String> difference2_2 = new ArrayList<>(list2);

difference2_2.removeAll(list1);

System.out.println("List2 - List1 (差集): " + difference2_2);

System.out.println();

// 方法3: 使用Set (适用于需要去重的场景)

System.out.println("=== 使用Set方法 ===");

Set<String> set1 = new HashSet<>(list1);

Set<String> set2 = new HashSet<>(list2);

// 交集

Set<String> intersectionSet = new HashSet<>(set1);

intersectionSet.retainAll(set2);

System.out.println("交集: " + intersectionSet);

// 差集

Set<String> differenceSet1 = new HashSet<>(set1);

differenceSet1.removeAll(set2);

System.out.println("List1 - List2 (差集): " + differenceSet1);

Set<String> differenceSet2 = new HashSet<>(set2);

differenceSet2.removeAll(set1);

System.out.println("List2 - List1 (差集): " + differenceSet2);

// 并集

Set<String> union = new HashSet<>(set1);

union.addAll(set2);

System.out.println("并集: " + union);

System.out.println();

// 性能比较示例

System.out.println("=== 性能比较 ===");

List<Integer> largeList1 = new ArrayList<>();

List<Integer> largeList2 = new ArrayList<>();

// 创建大数据集

for (int i = 0; i < 10000; i++) {

largeList1.add(i);

if (i % 2 == 0) {

largeList2.add(i);

}

}

long startTime = System.currentTimeMillis();

List<Integer> intersectionLarge = largeList1.stream()

.filter(largeList2::contains)

.collect(Collectors.toList());

long streamTime = System.currentTimeMillis() - startTime;

startTime = System.currentTimeMillis();

List<Integer> intersectionLarge2 = new ArrayList<>(largeList1);

intersectionLarge2.retainAll(largeList2);

long collectionTime = System.currentTimeMillis() - startTime;

startTime = System.currentTimeMillis();

Set<Integer> setLarge1 = new HashSet<>(largeList1);

Set<Integer> setLarge2 = new HashSet<>(largeList2);

setLarge1.retainAll(setLarge2);

long setTime = System.currentTimeMillis() - startTime;

System.out.println("大数据集性能比较:");

System.out.println("Stream API 耗时: " + streamTime + "ms");

System.out.println("Collection方法耗时: " + collectionTime + "ms");

System.out.println("Set方法耗时: " + setTime + "ms");

}

}