java - “if(map.get(key)-map1.getOrDefault(key, 0)!=0)”和“if(map.get(key)!=map1.getOrDefault(key, 0))”有什么区别

Question

我有以下代码-

package DP.permutation_in_string;

import java.util.HashMap;
import java.util.Map;

public class LeetCode {
    public static boolean checkInclusion(String s1, String s2) {
        Map<Character, Integer> map = new HashMap<>();
        
        for(int i=0; i<s1.length(); i++){
            map.put(s1.charAt(i), map.getOrDefault(s1.charAt(i), 0)+1);
        }

        for(int i=0; i<=s2.length()-s1.length(); i++){
                Map<Character, Integer> map1 = new HashMap<>();
         
                for(int j=i; j<i+s1.length();j++){
                    map1.put(s2.charAt(j), map1.getOrDefault(s2.charAt(j),0)+1);
                }
                
                if(mapCompare(map, map1))
                    return true;
        }
        
        return false;
    }
    
    static boolean mapCompare(Map<Character, Integer> map, Map<Character, Integer> map1){
        for(char key:map.keySet())
            //if(map.get(key)!=map1.getOrDefault(key, 0))
            if(map.get(key)-map1.getOrDefault(key, 0)!=0)
                return false;
        
        return true;
    }
    public static void main(String[] args) {
        String s1="ckzviabspcfbabslodcxtzanlsnwbqrozvnfadhtskosxhxaxzwcthvirwivsfuyxgkdvvdmmaoohvnfegkzdajhzibfiuxvsihpseyyiapmgldyojfselzzudzrxcksvfoqoeimyfhnvidryqhhpvjawwpzspcfnvmewnhcbbbwfjifmcuspbrrjyhcusyiuydscwenyicdlfzaoaiudsdyjmhmzwmeaozheiaddevjrrgsfgqnyeoyxfvktctazsfizkynlookeorzmdvtloyfpbqjgzhjvykdthwkuubnbalrddjxpizysaptrinlytecouekkpsfzbjaitckodcdinydtaaakbntwbvrcabylllxtgtkdqfkjggvbrnxnvcsfpcutabvazyeqzitpwhhdpcxaklhbjrcsqzveytzbgoeqnyrbkvkfnlqhrnedjomfmkuadwabnzomgvtdypocbvipryedcxnrcrqwpefqducxxilhpoewlliilidxucjydpahcumngpekrlroftwpbaejfjmohnkulxdglcpcszpyqestonhxskshzmdkikjkeymddyiysmigvqjveocbabhcofwyseytwfgiqmufcqrugwofytxzwwwiwlxdshtamwneosotqbfjjdxmhjkmzcvpmkuumycqzvlmwvjdwkcikyewupwaotrseyomhuykdkohveftgqfoqjcnstlxdasnvimslmuqsqrhvbukyfvpswmlavtxegbcesxgzswwnslxymmrdwmpalcazukvyyotlvwvlishtgbmlznrmcjysjemwqfjgbehnowgjlvtgemlkkdqpxiuqwhqkqdkexoflxfescoblknurkntbpfqfiervqgeiasguycmjoyzyujgzdfjobrswjpxixmadnnkdtazbasmnnlbubokkvomtupdpqwnoddummmqbwbthfhqdgdawdwxlmgvelhefvqcrpxbkgvhyrpxmfivrvkkqfpxjhzqesiqoeanqzpvbgonwptzqgtajoiiphivxtefarwjyoklkxumrndswebdsgiipzrcunpnibmxwlkihnzlswaujflztxxnuhojrpkzldwhnuiizxalawskkvaplopthvzjrbqfwpwjfkzrhyciajdsaeusctnvajuubjiqdqsaqjxtxgxabpdwxzgiedyyeosfdbkairekywkilyksjratftctphompqoomxucysbzrpywjzumoiizklkooilgeapimiixawfgiszfqucihxfrtrwijyeiebudncwnxbnafohhhqaltksafjfegxlbbewetsyrtuxxlngffpcnyfdarqwznsuiuhvqshjpvbiqkxgfwyrkdlorlwgexfinunbfzifxlfufalbkyfdekhupuuflsetpbppaahwbtjpjguygpnavimbbaeikwjxurdxyfgmldgdbkyxzhvwlxzlpnpmzlyosvhngmuqkrvcsabhiahhguxuakphuaptbjfpxybqnlfazkagwlbvzcnzorpymafiwvtkjtilwihwoyelogtpdyipzkurqcghpdqgrfpnmrmahbkbyupxwooblaydongjrlnuhoikoyiexgzlzgonceyhfwypsgypilxcnkdhxvbfddnhvdicolrjyzttrymmcvoyswaszbbugsuuewhewtoxgnrbfqsysjqqcutoikssesxaohxxfxofiguvpgzfkimmqdjuyljlpndapzygidopwxnaetmmpyaqozybbpfqlonebiilvckmtyaommksfcrmdeyjjbjncmpruofaaccnvndkovjugcrzcwkbdhqdiwnvnavnngloshyataygyukrecamzftmeephucmofjgrzsexsprpdkazhmtaepqppgzjmxxzlpbkouqlhqcxdpaslrjrsnfbjvbekpyqsldzhxarpzbbjteudfwfjdipgcdwylorxivwbjkegazpcngzkokygjfnmfeumbetznsxsmyhccurqdzznvhrtawpklrrrbedqzkiczignlaoaiydezgktdecaxwxxecymbuisvhlcjlhmnpjuegnaawfxopvvkxihehquxzlveabigomeptsqbfurytjikpbtsotgfghadilylnimxcsvgtmzjgxjyhabtfawzmomctquctwnolglflghdugeutgdmkitunbkhgoceqyrzvwprotiysaiqcnwxflcjgjqobeskizjqqwihnmxyvbeeufyvouupnyuuyauxtmhtqlbgoacjdkvmuqohbkpctfwxvwlghevsuozrgxkrrrllnvjloeligxvnvzluxlajszgeilxdjaviawhlthtxuclqypgdiwgwrhynmzqghyzeednlmyepgxxvtmjsuprisbgyvcojhculwdkjmpmvueaftiujrmdqptrmlrwdyjtjlznuhftzmffbcqsjemrpjrqxtuxhlnqvckgcuvhswgtxonfljjwnexdafpjzwjdypdfwhwogikkpsvuckmgehcqmdecriamdqsdsxuhsdqenrpifzjnpvrbpvetatbmvsncltabzspzedumeclbxiqnsmdkbqfedikoalfsnxkhewwzyeqxlecfimvdpxdnvrtlxlxzakupknvchursvilyjyfxmvdeojclhjjwxtpqiogsfdnzchrlztvxmibbociiberaevpjmyqxvcicxuwkmyjlgxhvrjdqbjzdctzwidoplkvazhgsdbkavmrpfjgebydmloykqtxocdhcpwrtvawhofvwnohtwodppmcrbhvrvexzijiwgkptntyljvikjlzpjvpxaejfwzyldxrckbzylvhpqmjjeyatmrbcgozvcalcctngwuysjqmkmhjwmyyfxhdjswimahqzptrphtjekkabpgopfdnhwaclxzavftmswadgztxceonrkczurtdvxhabiafyzdbdbyorerekjzgpueihiamlscdndjjgqwdjsmeweqrfpypfrfsciclvrrqchnmtxscbvbbipzingkeopuvlnpqaeqidlpvusbkjhntvxbookqctymjmhqjvsnaiblmnofxphanpxspmkmxmyejooqpytdixgguonbpaipurpwwfqxrrtekvvtpgndabbvjcoxonxciuypxqcfolxirvafnmgsrcrenwyuxfekuqyfdtvhvmonvkstbmvygsbguiknltpixsebxktczniurulxpyxckrtmhpvgqpbvlqwvcqwaocalqtdwomgrjyvryodeikbeeebcrrkugliqgktoohsneynmfafykpmndfgwtpdwfrmicenyntbfyyntlqqrujfioycrhopgiadmsjcycucyuqvzufbvachmlwyfxspzrvkkvkhuykoqrwshzmyypmvosuezpsgtqtecayj";
        String s2="livsugnixbcmmajhinduvzfjzxtzneixibupxfezifaovcbowfayjtlcdsjogjytuczxbwluiktkdyecquebuvkgfobhpiqfbyckfbchvfkdowckrvuiblhbmubugrrovdhbyvevwetlusthiyxgtaqcdfytgbkrnnjifdslzntgnryqcmwkumdvqctymyffanmawobfihsfqmtqvivvouunsexpzcfmiituppwxgjyspyoeuspyystyneoonatbojiufzhhfeakqzeypaopkyscadbkzsnnjewgflysazhwaigicrzeccanemfmrvrdzxtcbuqvjblrynlhbmtkzhtiqnhrfclxovtijwucgvsreirqmhweoazxdyydksrchvizmljhdkekaxbqkleaolqnepijxpwbcxfadfsxswhzmmffsmoiyfosbwjjcgqpexddwizaiqpsaagwxkajdhqeyouihwlfrmnelakembxwcrvwqyaguvqewjczfmfqiqmjbqxcmfrpqoewszkomwckfgrlkannjefxsulbpkpxlvbrgwruvhdonuezoomvnyridrosfzhfvhmqbzdsfvjgfdqvafheuhveaqwrofhgkfobkkevdsqyumzrvapfjypvjsdzaxxwcnsbxasqewmkmucxbgjqntdsvrbndebttkoiznatcjgtgklljurkkdvpbrtbolvgrqwsnuoubhgvtmbakwgvxypndpqtireuvbdxfjcioqqsbfrqahqsfbwfnlkwobnqdbptxrizourrxyjejflgkbcwmrtttqeeqkyzrzdcfakwcfajhjfmcpnsbekwtzgpbwrotgsxopaemsnywoxsqxoyricgosfurfggulchgyoocivnkqytgbroijmaduoywbudtgwugekikebdadoygtmikcficifdcsvritesbvznlbrgbveudwzatarhbehowrrakimocgqyxzedhlqxzxtqloupbwbdvewcbehkmoahoykouhilivtxukqhwmyjjqmfxqybahsubfvnhctudtpxwsnwfmsamavjkqiabzzcqgqssygswavqpdtxfyognqybsogsbkzkktfjqebhitvqnawokacbkfkthqoammdscyvxgaaqyaplexhlwweambfwtylvihpdedshaeluxgthrejkgkvwrtyzpuygqghtlkmpnzkyjiwyuaqijkxttvdsxddfkmgnnlmamjumsbjmjxqkrgncrwyoyetdsmtanoasirkfklcsxukfdebnlbgobwgyqrthzwjbwpxuxmheplqyjaucgrptfewjahejsfypktnpafmlrzekbjqsgthrwbdxttitsqyglsjgnzmscncgvkooxdlxsmmugeeayicndgoagpfckerzuwdphqksijniyckzviabspcfbabslodcxtzanlsnwbqrozvnfadhtskosxhxaxzwcthvirwivsfuyxgkdvvdmmaoohvnfegkzdajhzibfiuxvsihpseyyiapmgldyojfselzzudzrxcksvfoqoeimyfhnvidryqhhpvjawwpzspcfnvmewnhcbbbwfjifmcuspbrrjyhcusyiuydscwenyicdlfznoaiudsdyjmcmzwmeaozheiaddevjrrgsfgqnyeoyxfvktctazsfizkynlookeorzmdvtloyfpbqjgzhjvykdthwkuubnbalrddjxpihysaptrinlytecouekkpsfzbjaitckodcdinydtaaakbntwbvrcasylllxtgtkdqfkjggvbanxnvcsfphutabvazyeqzitpwhhdpcxaklhbjrcsqzveytzbgoeqnyrbkvkfnlqhrnedjomfmkuadwabnzomgvtdypocbvipryedcxnrcrqwpefqducxxilhpoewlliilidxucjydpahcumagpekrlroftwpbaejfjmohnkulxdglcpcszpyqestonhxskshzmdkikjkeymdfyiysmigvqjveocbabhcofwyseytwfgiqmufcqrugwofytxzwwwiwlxdshtamwneosotqbfjjdxmhjkmzcvpmkuumycqzvlmwvjdwkcityewupwaotrseyomhuykdkohveftgqfoqjcnstlxdasnvimslmuqsqrhvbukyfvpswmlavtxegbcesxgzswwnslxymmrdwmpalcazukvyyotlvwvlishtgbmlznrmcjysjemwqfjgbehnowgjlvtgemlkkdqpxiuqwhqkqdkexoflxfescoblknurkntbpfqfiervqgeiesguycmjoyzyujgzdfjobrswjpxixmadnnkdtazbasmnnlbubokkvomtupdpqwnoddummmqbwbthfhqdgdawdwxlmgvelhefvqcrpxbkgvhyrpxmfivrvkkqfpxjhzqesiqoeanqzpvbgonwptzqgtajoiiphivxtefarwjyoklkxumrndswebdsghipzrcunpnibmxwlkihnzlswaujflztxxnuhojrpkzldwhnuiizxalawskkvaplopthvzjrbqfwpwjfkzrhyciajdsaeusctnvajuubjiqdqsaqjxtxgxabpdwxzgiedyyeosfdbkrirekywkilyksjratftctphompqoomxucysbzrpywjzumoiizklkooilgeapimiixawfgiszfqucihxfrtrwijyeiebudncwnxbnafohhhqaltksafjfegxlbbewetsyrtuxxlngffpcnyfdarqwznsuiuhvqshjpvbiqkxgfwyrkdlorlwgexfinunbfzifxlfufalbkyddekhupuuflsetpbppaahwbkjpjguygpnavimbbaeikwjxurdxyfgmldgdbkyxzhvwlxzlpnpmzlyosvhngmuqkrvcsabhiahhguxuakphuaptbjfpxybqnlfazkagwlbvzcnzorpymafiwvtkjtilwihwoyelogtpdyipzkurqcghpdqgrfpnmrmahbkbyupxwooblaydongjrlnuhoikoyiexgzlzgonceyhfwypsgypilxcnkdhxvbfddnhvdicolrjyzttrymmcvoyswaszbbugsuuewhawtoxgnrbfqsysjqqcutoikssesxaohxxfxofiguvpgzfkimmqdjuyljlpndapzygidopwxnaetmmpyaqozybbpfqlonebiilvckmtyaommksfcrmdeyjjbjncmpruofaaccnvndkovjugcrzcwkbdhqdiwnvnavnngloshyataygyukrecamzftmeephucmofjgrzsepsprpdkazhmtaepqppgzjmxxzlpbkouqlhqcxdpaslrjrsnfbjvbekpyqsldzhxarpzbbjteudfwfjdipgcdwylorxivwbjkegazpcngzkokygjfnmfeumbetznsxsmyhccurqdzznvhrtawpklrrrbedqzkiczignlaoaiydezgktdecaxwxxecymbuisvhlcjlhmnpjuegnaawfxopvvkxihehquxzlveabigomeptsqbfurytjikpbtsotgfghadilylnimxcsvgtmzjgxjyhabtfawzmomctquctwnolglflghdugeutgdmkitunbkhgoceqyrzvwprotiysaiqcnwnflcjgjqobeskizjqqwihnmxyvbeeufyvouupnyuuyauxtmhtqlbgoacjdkvmuqohbkpctfwxvwlgievsuozrgxkrrrllnvjloeligxvnvzluxlajszgeilxdjaviawhlthtxuclqypgdiwgwrhynmzqghyzeednlmyepgxxvtmjsuprisbgyvcojhculwdkjmpmvueaftiujrmdqptrmlrwdyjtjlznuhftzmffbcqsjemrpjrqxtuxhlnqvckgcuvhswgtxonfljjwnexdafpjzwjdypdfwhwogikkpsvuckmgehcqmdecriamdqsdsxuhsdqenrpifzjnpvrbpvetatbmvsncltabzspzedumeclbxiqnsmdkbqfedikoalfsnxkhewwzyeqxlecfimvdpxdnvrtlxlxzakupknvchursvilyjyfxmvdfojclhjjwxtpqiogsfdxzczrlztvxmibbociiberaevpjmyqxvcicxuwkmyjlgxhvrjdqbjzdctzwidoplkvazhgsdbkavmrpfjgebydmloykqtxocdhcpwrtvawhofvwnohtwodxpmcrbhvrvexzijiwgkptntyljvikjlzpjvpxaejfwzyldxrckbzylvhpqmjjeyatmrbcgozvcalcctngwuysjqmkmhjwmyyfxhdjswimahqzptrphtjekkabpgopfdnhwaclxzavftmswadgztxceonrkczurtdvxhabiafyzdbdbyorerekjzgpueihiamlscdndjjgqwdjsmeweqrfpypfrfsciclvrrqchnmtxscbvbbipzingkeopuvlnpqaeqidlpvusbkjhntvxbookqctymjmhqjvsnaiblmnofxphanpxspmkmxmyejooqpytdixgguonbpaipurpwwfqxrrtekvvtpgndabbvjcoxonxciuypxqcfolxirvafnmgsrcrenwyuxeekuqyfdtvhvmonvkbtbmvygsbguiknltpixsebxktczniurulxpyxckrtmhpvgqpbvlqwvcqwaocalqtdwomgrjyvryodeikbeeebcrrkugliqgktoohsneynmfafykpmndfgwtpdwfrmicenyntbfyyntlqqrujfioycrhopgiadmsjcycucyuqvzufbvachmlwyfxspzrvkkvkhuykoqrwshzmyypmvosuezpsgtqtecayjdasrysrmdewxmqntqmuavczczrcrzokjzqtiucdfmijfqkizfftxsddkdwlofkjbuhzodgzeslpezdifpdfktufgekrrbsxfeqduphoemwhncbblqkoyychuwlkjfxjmvdasfhwxnxjmstabgiujditpmpnojsfzpgqvupkdipphutiewfynvoxmdaloyxsksaxnyyizreshgejskhokarxddrrkoeglwledovrbarhkfcetrshiuucmbrtqjawsavbhuoijshkzcmogbjurybhwduushlmhjzgthhlvftpytayjzzbcxbtvozwhsmtkltgrugyfaoldnnswbohpsqvwbwtjcxeewsvfwpkwltxmomlwsylwvcmmrwjvvbbktqxnypfmhjigzaqacmprjfnooinkgbjzzwyuafxsmqdcmsxhbfoejjzxizufvfejrrcfaijqovlxdngkgwisvryevivawbcttftuxympktxbxotvdycxhfokmtdeqacdceffvhvjpnzfuhqslixvlcxehvbkritokoqqlbmkdkgflthhhdgiaidjjpvcatctiosolfqzcjmdppttztpklgosnshspna";
        System.out.println(checkInclusion(s1, s2));
    }

}

使用if(map.get(key)-map1.getOrDefault(key, 0)!=0)工作正常但不是if(map.get(key)!=map1.getOrDefault(key, 0))。这背后的原因是什么？

标签： javahashmap

Answer 1

映射存储引用类型的键和值。您的地图存储Integers。

map.get(key)是Integer, 是map1.getOrDefault(key, 0). 如果您使用 比较它们!=，您正在比较身份的参考；也就是说，它们是同一个实例。例如，new Integer(0) == new Integer(0)是错误的，即使它们都是Integer包装的实例int 0。

但是，如果减去两个Integers，它们将被取消装箱，因为二进制数字提升。new Integer(0) - new Integer(0) == 0, 因为每个new Integer(0)都拆箱到0, 和0 - 0 == 0.

!A.equals(B)如果您使用而不是 ，您将得到相同的答案A != B，因为这是通过（不）平等而不是身份进行比较。例如：

if(!map.get(key).equals(map1.getOrDefault(key, 0)))

或者，您可以使用Integer.compare：

if(Integer.compare(map.get(key), map1.getOrDefault(key, 0)) != 0)

或显式拆箱：

if(map.get(key).intValue() != map1.getOrDefault(key, 0).intValue())