获取两个List的不同元素

/**

* 几种不同的方法，查询效率不同
*getDiffrent5()效率最高
*/

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
* 获取两个List集合中的不相同的对象
*/
public class Test2ListDiff {

public static void main(String[] args) {
List<String> list1 = new ArrayList<String>();
List<String> list2 = new ArrayList<String>();
int num = 5;
// int num=5000;
for (int i = 0; i < num; i++) {
list1.add("test_" + i);
list2.add("test_" + i * 2);
}

getDiffrent3(list1, list2);
getDiffrent5(list1, list2);
getDiffrent4(list1, list2);
getDiffrent2(list1, list2);
getDiffrent(list1, list2);

// getDiffrent3 total times 32271699
// getDiffrent5 total times 12239545
// getDiffrent4 total times 16786491
// getDiffrent2 total times 2438731459
}

/**
* 获取两个List的不同元素
*
* @param list1
* @param list2
* @return
*/
private static List<String> getDiffrent5(List<String> list1, List<String> list2) {
long st = System.nanoTime();
List<String> diff = new ArrayList<String>();
List<String> maxList = list1;
List<String> minList = list2;
if (list2.size() > list1.size()) {
maxList = list2;
minList = list1;
}

// 将List中的数据存到Map中
Map<String, Integer> maxMap = new HashMap<String, Integer>(maxList.size());
for (String string : maxList) {
maxMap.put(string, 1);
}

// max:1,2,3,4,5
// min:2,4,6,8,10

// 循环minList中的值，标记 maxMap中 相同的 数据2
for (String string : minList) {
// 相同的
if (maxMap.get(string) != null) {
maxMap.put(string, 2);
continue;
}
// 不相等的
diff.add(string);
}
printf(diff);

// 循环maxMap
for (Map.Entry<String, Integer> entry : maxMap.entrySet()) {
if (entry.getValue() == 1) {
diff.add(entry.getKey());
}
}
printf(diff);

System.out.println("getDiffrent5 total times " + (System.nanoTime() - st));
return diff;
}

/**
* 获取两个List的不同元素
*
* @param list1
* @param list2
* @return
*/
private static List<String> getDiffrent4(List<String> list1, List<String> list2) {
long st = System.nanoTime();
Map<String, Integer> map = new HashMap<String, Integer>(list1.size() + list2.size());
List<String> diff = new ArrayList<String>();
List<String> maxList = list1;
List<String> minList = list2;
if (list2.size() > list1.size()) {
maxList = list2;
minList = list1;
}
for (String string : maxList) {
map.put(string, 1);
}
for (String string : minList) {
Integer cc = map.get(string);
if (cc != null) {
map.put(string, ++cc);
continue;
}
map.put(string, 1);
}
for (Map.Entry<String, Integer> entry : map.entrySet()) {
if (entry.getValue() == 1) {
diff.add(entry.getKey());
}
}
System.out.println("getDiffrent4 total times " + (System.nanoTime() - st));
return diff;
}

/**
* 获取两个List的不同元素
*
* @param list1
* @param list2
* @return
*/
private static List<String> getDiffrent3(List<String> list1, List<String> list2) {
long st = System.nanoTime();
Map<String, Integer> map = new HashMap<String, Integer>(list1.size() + list2.size());
List<String> diff = new ArrayList<String>();
for (String string : list1) {
map.put(string, 1);
}
for (String string : list2) {
Integer cc = map.get(string);
if (cc != null) {
map.put(string, ++cc);
continue;
}
map.put(string, 1);
}
for (Map.Entry<String, Integer> entry : map.entrySet()) {
if (entry.getValue() == 1) {
diff.add(entry.getKey());
}
}
System.out.println("getDiffrent3 total times " + (System.nanoTime() - st));
return diff;
}

/**
* 获取连个List的不同元素
*
* @param list1
* @param list2
* @return
*/
private static List<String> getDiffrent2(List<String> list1, List<String> list2) {
long st = System.nanoTime();
list1.retainAll(list2);
System.out.println("getDiffrent2 total times " + (System.nanoTime() - st));
return list1;
}

/**
* 获取两个List的不同元素
*
* @param list1
* @param list2
* @return
*/
private static List<String> getDiffrent(List<String> list1, List<String> list2) {
long st = System.nanoTime();
List<String> diff = new ArrayList<String>();
for (String str : list1) {
if (!list2.contains(str)) {
diff.add(str);
}
}
System.out.println("getDiffrent total times " + (System.nanoTime() - st));
return diff;
}

public static void printf(List<String> list) {
System.out.println("----------------------------");
for (int i = 0; i < list.size(); i++) {
System.out.println(list.get(i));
}
}