高效的找出两个List中的不同元素
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/** TestList.java* Version 1.0.0* Created on 2017年12月15日* Copyright ReYo.Cn*/package reyo.sdk.utils.test.list2;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class TestList { public static void main(String[] args) { List<String> list1 = new ArrayList<String>(); List<String> list2 = new ArrayList<String>(); for (int i = 0; i < 10000; i++) { list1.add("test" + i); list2.add("test" + i * 2); } getDiffrent(list1, list2); getDiffrent3(list1, list2); getDiffrent5(list1, list2); getDiffrent4(list1, list2); getDiffrent2(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; } Map<String, Integer> map = new HashMap<String, Integer>(maxList.size()); for (String string : maxList) { map.put(string, 1); } for (String string : minList) { if (map.get(string) != null) { map.put(string, 2); continue; } diff.add(string); } for (Map.Entry<String, Integer> entry : map.entrySet()) { if (entry.getValue() == 1) { diff.add(entry.getKey()); } } 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; }} |
getDiffrent total times 320118400
getDiffrent3 total times 12051500
getDiffrent5 total times 6301100
getDiffrent4 total times 7527300
getDiffrent2 total times 298880900
