Java第08章-集合操作

1 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 2 java util Arrays类Thisclasscontainsvariousmethodsformanipulatingarrays排序 sorting 搜索 searching 填充 filling 对数组对象的操作 Arrays 3 全部是静态方法publicstaticintbinarySearch byte a bytekey Searchesthespecifiedarrayofbytesforthespecifiedvalueusingthebinarysearchalgorithm publicstaticbooleanequals byte a byte a2 Returnstrueifthetwospecifiedarraysofbytesareequaltooneanother publicstaticvoidfill byte a byteval Assignsthespecifiedbytevaluetoeachelementofthespecifiedarrayofbytes publicstaticvoidfill byte a intfromIndex inttoIndex byteval Assignsthespecifiedbytevaluetoeachelementofthespecifiedrangeofthespecifiedarrayofbytes publicstaticvoidsort byte a Sortsthespecifiedarrayofbytesintoascendingnumericalorder 对数组对象的操作 Arrays boolean char byte short int long double float Object 4 对数组对象的操作 Arrays importjava util Arrays publicclassArrayDemo1 publicstaticvoidmain Stringargs int a1 newint 10 int a2 newint 10 Arrays fill a1 47 Arrays fill a2 47 System out println Arrays equals a1 a2 a2 3 11 a2 2 9 System out println Arrays equals a1 a2 Arrays sort a2 System out println Arrays binarySearch a2 11 5 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 6 数学上 集合 概念的抽象 无序ASetisacollectionthatcannotcontainduplicateelements 集合与元素集合之间无序集合和有序集合 对象集合 Set 7 java util Set接口 集合与元素 publicbooleanadd Objecto Addsthespecifiedelementtothissetifitisnotalreadypresent publicbooleanremove Objecto Removesthespecifiedelementfromthissetifitispresent publicbooleancontains Objecto Returnstrueifthissetcontainsthespecifiedelement publicintsize Returnsthenumberofelementsinthisset 对象集合 Set 8 java util HashSetimplementjava util Set无序集合 对象集合 Set importjava util publicclassSetDemo1 publicstaticvoidmain Stringargs Sets newHashSet for inti 0 i args length i if s add args i System out println Duplicate args i System out println s size distinctwords s D javaFindDups1icameisawileftDuplicate iDuplicate i4distinctwords came left saw i D 9 java util Set接口 集合之间 publicbooleancontainsAll Collectionc Returnstrueifthissetcontainsalloftheelementsofthespecifiedcollection publicbooleanaddAll Collectionc Addsalloftheelementsinthespecifiedcollectiontothissetifthey renotalreadypresent publicbooleanremoveAll Collectionc Removesfromthissetallofitselementsthatarecontainedinthespecifiedcollection publicbooleanretainAll Collectionc Retainsonlytheelementsinthissetthatarecontainedinthespecifiedcollection 对象集合 Set 10 java util HashSetimplementjava util Set 对象集合 Set importjava util publicclassSetDemo2 publicstaticvoidmain Stringargs Setuniques newHashSet Setdups newHashSet for inti 0 i args length i if uniques add args i dups add args i uniques removeAll dups System out println Uniquewords uniques System out println Duplicatewords dups D javaFindDups2icameisawileftUniquewords came left saw Duplicatewords i D 11 HashSet 无序集合 对象集合 Set importjava util publicclassSetDemo3 publicstaticvoidmain Stringargs booleanb Sets newHashSet b s add string1 System out println string1addreturns b b s add string2 System out println string2addreturns b b s add string3 System out println string3addreturns b b s add string1 System out println string1addreturns b b s add string2 System out println string2addreturns b Iteratori s iterator while i hasNext System out println i next D javaSetDemo3string1addreturnstruestring2addreturnstruestring3addreturnstruestring1addreturnsfalsestring2addreturnsfalsestring3string1string2D java util Iterator迭代器 interface 轮循 无序输出 12 对象集合 Set java util Set interface java util SortedSet interface java util HashSet class java util TreeSet class 无序集合 有序集合 HashSet SetimplementedviaahashtableTreeSet SortedSetimplementedasatree 13 java util TreeSetimplementjava util SortedSet 对象集合 Set importjava util publicclassSetDemo4 publicstaticvoidmain Stringargs booleanb Sets newTreeSet b s add string1 System out println string1addreturns b b s add string2 System out println string2addreturns b b s add string3 System out println string3addreturns b b s add string1 System out println string1addreturns b b s add string2 System out println string2addreturns b Iteratori s iterator while i hasNext System out println i next D javaSetDemo4string1addreturnstruestring2addreturnstruestring3addreturnstruestring1addreturnsfalsestring2addreturnsfalsestring1string2string3D java util Iterator迭代器 interface 轮循 有序输出 自然顺序 14 对象集合 Set importjava util publicclassSetDemo5 publicstaticvoidmain Stringargs Sets newHashSet s add 37 s add newInteger 37 Iteratori s iterator while i hasNext System out println i next createasetandaddtwoobjectstoit theobjectsaredistinctbuthavethesamedisplayablestring D javaSetDemo53737D 15 对象集合 Set importjava util publicclassSetDemo6 publicstaticvoidmain Stringargs Sets newTreeSet s add 37 s add newInteger 37 Iteratori s iterator while i hasNext System out println i next createaSortedSet addtwoobjectstotheset theobjectsarenotcomparable D javaSetDemo6Exceptioninthread main java lang ClassCastExceptionD Theexceptionisthrownbecauseanattemptismadetoordertheelementsoftheset AStringobjecthasnorelationshiptoanIntegerobject sotherelativeorderofthetwoobjectscannotbedetermined 16 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 17 有序对象的集合AListisanorderedcollection sometimescalledasequence Listscancontainduplicateelements Theusercanaccesselementsbytheirintegerindex position andsearchforelementsinthelist 方法操作列表与元素列表之间 对象列表 List 18 java util List接口 列表与元素 publicvoidadd intindex Objectelement Insertsthespecifiedelementatthespecifiedpositioninthislist publicObjectremove intindex Removestheelementatthespecifiedpositioninthislist publicbooleancontains Objecto Returnstrueifthislistcontainsthespecifiedelement publicintindexOf Objecto Returnstheindexinthislistofthefirstoccurrenceofthespecifiedelement or 1ifthislistdoesnotcontainthiselement 对象列表 List 19 java util List接口 列表之间 publicbooleanaddAll Collectionc Appendsalloftheelementsinthespecifiedcollectiontotheendofthislist publicbooleanremoveAll Collectionc Removesfromthislistalltheelementsthatarecontainedinthespecifiedcollection publicbooleancontainsAll Collectionc Returnstrueifthislistcontainsalloftheelementsofthespecifiedcollection publicbooleanretainAll Collectionc Retainsonlytheelementsinthislistthatarecontainedinthespecifiedcollection 对象列表 List 20 java util ArrayListimplementsjava util List importjava util publicclassListDemo1 publicstaticvoidmain Stringargs Listlist newArrayList for inti 1 i 10 i list add i i i i Iteratoriter list iterator while iter hasNext System out println iter next D javaListDemo11 1 12 2 43 3 94 4 165 5 256 6 367 7 498 8 649 9 8110 10 100D 对象列表 List 21 对象列表 List java util List interface java util AbstractSequentialList class java util AbstractList class java util LinkedList class java util ArrayList class ArrayList ListimplementedviaanarrayLinkedList Listimplementedasalinkedstructure 22 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 23 AMapisanobjectthatmapskeystovaluesAmapcannotcontainduplicatekeys Eachkeycanmaptoatmostonevalue 对象映射 Map Key1 键 Value1 值 Key2 键 Value2 值 Keyn 键 Valuen 值 Map Entry1 Entry2 Entryn 24 对象映射 Map 对象列表 List java util Map interface java util AbstractMap class java util HashMap class HashMap MapimplementedviaahashtableTreeMap SortedMapimplementedasatree java util TreeMap class 25 对象映射 Map publicinterfaceMap 基本操作Objectput Objectkey Objectvalue Objectget Objectkey Objectremove Objectkey booleancontainsKey Objectkey booleancontainsValue Objectvalue intsize booleanisEmpty 批量操作voidputAll Mapt voidclear CollectionViewspublicSetkeySet publicCollectionvalues publicSetentrySet publicinterfaceEntry ObjectgetKey ObjectgetValue ObjectsetValue Objectvalue java uitl Map接口 26 对象映射 Map importjava util publicclassMapDemo1 privatestaticfinalIntegerONE newInteger 1 publicstaticvoidmain Stringargs Mapm newHashMap for inti 0 i args length i Integerfreq Integer m get args i m put args i freq null ONE newInteger freq intValue 1 System out println m size distinctwordsdetected System out println m java uitl HashMapimplementsjava util Map interfaceMappublicObjectget Objectkey publicObjectput Objectkey Objectvalue D javaMapDemo1ifitistobeitisuptometodelegate8distinctwordsdetected to 3 me 1 delegate 1 it 2 is 2 if 1 be 1 up 1 27 对象映射 Map importjava util publicclassMapDemo2 publicstaticvoidmain Stringargs Mapm newHashMap m put Mary 123 4567 m put Larry 234 5678 m put Mary 456 7890 Iteratoriter m entrySet iterator while iter hasNext Map Entrye Map Entry iter next System out println e getKey e getValue java uitl HashMapimplementsjava util Map 28 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 29 java util Collections类仅仅包含静态方法对列表 List 的操作查询 binarySearch 拷贝 copy 填充 fill 洗牌 shuffle 倒转 reverse 排序 sort 交换 swap 对集合类 Collection 的操作最大 最小同步处理集合类 Collection 列表 List 映射图 Map 集合 Set 不可修改 只读 处理集合类 Collection 列表 List 映射图 Map 集合 Set 对对象数组的操作 Collections 可类比于java util Arrays类 30 利用Collections类排序 指定排序方法 对对象数组的操作 Collections importjava util publicclassSortDemo publicstaticvoidmain Stringargs Listlist newArrayList list add abc list add DEF list add ghi Collections sort list Iteratoriter list iterator while iter hasNext System out println iter next Collections sort list newMySort iter list iterator while iter hasNext System out println iter next importjava util classMySortimplementsComparator publicintcompare Objecto1 Objecto2 Strings1 String o1 Strings2 String o2 pareToIgnoreCase s2 classCollectionspublicstaticvoidsort Listlist Sortsthespecifiedlistintoascendingorder accordingtothenaturalorderingofitselements classCollectionspublicstaticvoidsort Listlist Comparatorc SortsthespecifiedlistaccordingtotheorderInducedbythespecifiedcomparator interfacejava util Comparatorpublicintcompare Objecto1 Objecto2 publicbooleanequals Objectobj 31 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 32 java util Enumeration接口AnobjectthatimplementstheEnumerationinterfacegeneratesaseriesofelements oneatatime SuccessivecallstothenextElementmethodreturnsuccessiveelementsoftheseries 两个方法publicbooleanhasMoreElements publicObjectnextElement 示例 枚举 Enumeration for Enumeratione v elements e hasMoreElements System out println e nextElement 33 提供枚举方法的类及方法java util Hashtable类publicEnumerationelements publicEnumerationkeys java util Vector类publicEnuerationelements 来自JDK1 0注意ThefunctionalityofthisinterfaceisduplicatedbytheIteratorinterface Inaddition Iteratoraddsanoptionalremoveoperation andhasshortermethodnames NewimplementationsshouldconsiderusingIteratorinpreferencetoEnumeration 枚举 Enumeration 34 java util Iterator接口来自JDK1 2三个方法publicbooleanhasNext publicObjectnext publicvoidremove 示例 迭代 Iterator staticvoidfilter Collectionc for Iteratori c iterator i hasNext if cond i next i remove 35 对数组对象的操作 Arrays 对象集合 Set 对象列表 List 对象映射 Map 对对象数组的操作 Collections 枚举 Enumeration 和迭代 Iterator 小结 第八章集合操作 36 小结 接口的层次关系 37 java util HashSet类HashtableimplementationoftheSetinterface Thebestall aroundimplementationoftheSetinterface java util TreeSet类Red blacktreeimplementationoftheSortedSetinterface java util LinkedHashSet类HashtableandlinkedlistimplementationoftheSetinterface Aninsertion orderedSetimplementationthatrunsnearlyasfastasHashSet java util ArrayList类Resizable arrayimplementationoftheListinterface EssentiallyanunsynchronizedVector Thebestall aroundimplementationoftheListinterface 一般用途 38 java util LinkedList类Doubly linkedlistimplementationoftheListinterface MayprovidebetterperformancethantheArrayListimplementationifelementsarefrequentlyinsertedordeletedwithinthelist Usefulforqueuesanddouble endedqueues deques java util HashMap类HashtableimplementationoftheMapinterface E