目錄
0.知識概述:
1.集合
1.1 集合繼承關系類圖
1.2?集合遍歷的三種方式
1.3 集合排序
?1.3.1 Collections實現
1.3.2 自定義排序類
2 List 集合概述
2.1 ArrayList?
(1)特點
(2)常用方法
2.2 LinkedList
3. Set集合
3.1 概述
(1)特點
(2)重要方法
(3)Set集合的唯一性(hashCode() -> equals())
3.2 HashSet
3.3 LinkedHashSet
3.4 TreeSet
4.Map
4.1?概述
4.1.1 特點 & 繼承關系
4.1.2 遍歷集合的三種方式
4.2 HashMap
4.3 LinkedHashMap
4.4 TreeMap
0.知識概述:
1.集合
1.1 集合繼承關系類圖
1.2?集合遍歷的三種方式
/* 遍歷集合的三種方式:01 -> for 循環遍歷02 -> forEach 方法遍歷03 -> Iterator 迭代器遍歷*/
代碼實現:
System.out.println(dmList); //[斗羅, 滄源圖, 仙逆, 凡人, 斗破, 吞噬星空]/* 遍歷集合的三種方式:01 -> for 循環遍歷02 -> forEach 方法遍歷03 -> Iterator 迭代器遍歷*/// 法1:for(String dm: dmList){System.out.print(dm+" ");} //斗羅 滄源圖 仙逆 凡人 斗破 吞噬星空System.out.println();// 法2:dmList.forEach(dm->{System.out.print(dm + " "); //斗羅 滄源圖 仙逆 凡人 斗破 吞噬星空});System.out.println();// 法3:Iterator<String> itr = dmList.iterator();while(itr.hasNext()){String dm = itr.next(); // 提取下一個元素, 同時指針向后移動System.out.print(dm);} // 斗羅滄源圖仙逆凡人斗破吞噬星空System.out.println();
1.3 集合排序
?1.3.1 Collections實現
方式1: Collections.sort(list);方式2: 創建一個內部類繼承Comparator, 實現其compare
code:
public class ListSorter {// 方式1: Collections.sort(list);public static List<Integer> sort1(List<Integer> list){Collections.sort(list);System.out.println(list); //[18, 25, 45, 49]return list;}// 方式2: 創建一個內部類繼承Comparator, 實現其compareclass CompareDemo implements Comparator<Integer> {@Overridepublic int compare(Integer o1, Integer o2) {return o2 - o1;}}public List<Integer> sort2(List<Integer> list){Collections.sort(list, new CompareDemo());System.out.println(list); // [49, 45, 25, 18]return list;}public static void main(String[] args) {List<Integer> alist = new ArrayList<>();alist.add(25);alist.add(45);alist.add(49);alist.add(18);System.out.println(alist); //[25, 45, 49, 18]System.out.println(alist.toString()); //[25, 45, 49, 18]System.out.println(ListSorter.sort1(alist)); //[18, 25, 45, 49]ListSorter ls = new ListSorter();System.out.println(ls.sort2(alist)); //[49, 45, 25, 18]}
}
1.3.2 自定義排序類
public class TestSort {class CarSortDemo implements Comparator<Car> {// 01 比較car 對象
// @Override
// public int compare(Car o1, Car o2) {
// return o1.equals(o2) ? 0 : 1;
// }// 02 比較car 對象的 sn屬性值
// @Override
// public int compare(Car o1, Car o2) {
// return o1.getSn().compareTo(o2.getSn());
// }// 03 比較car 對象的 brand 屬性值public int compare(Car o1, Car o2){return o2.getModel().compareTo(o1.getModel());}}public List<Car> sort(List<Car> list){Collections.sort(list, new CarSortDemo());return list;}public static void main(String[] args) {List<Car> carsList = new ArrayList<>();carsList.add(new Car("217893","baoma"));carsList.add(new Car("689326","su7"));carsList.add(new Car("859032","aodi"));carsList.add(new Car("785932","benchi"));carsList.add(new Car("238979","biyadi"));System.out.println(carsList);
//[Car{sn='217893', model='baoma'}, Car{sn='689326', model='su7'}, Car{sn='859032', model='aodi'}, Car{sn='785932', model='benchi'}, Car{sn='238979', model='biyadi'}]System.out.println(new TestSort().sort(carsList));// 01 比較car 對象
//[Car{sn='217893', model='baoma'}, Car{sn='689326', model='su7'}, Car{sn='859032', model='aodi'}, Car{sn='785932', model='benchi'}, Car{sn='238979', model='biyadi'}]// 02 比較car 對象的 sn屬性值
//[Car{sn='217893', model='baoma'}, Car{sn='238979', model='biyadi'}, Car{sn='689326', model='su7'}, Car{sn='785932', model='benchi'}, Car{sn='859032', model='aodi'}]// 03 比較car 對象的 brand 屬性值
//[Car{sn='689326', model='su7'}, Car{sn='238979', model='biyadi'}, Car{sn='785932', model='benchi'}, Car{sn='217893', model='baoma'}, Car{sn='859032', model='aodi'}]}
}
2 List 集合概述
有關List的相關繼承關系:
2.1 ArrayList?
(1)特點
(2)常用方法
/*** ArrayList ->* 01. ArrayList<String> nickList = new ArrayList<String>();* 02. nickList.add("phdvb");* nickList.add(1,"pxq");* nickList.get(2)* 03. nickList.set(2, "drl");* 04. nickList.remove("phdvc");* remove(listSize-1);* nickList.size();*/
public class ArrayListDemo {public static void main(String[] args) {/*** ArrayList ->* 01. ArrayList<String> nickList = new ArrayList<String>();* 02. nickList.add("phdvb");* nickList.add(1,"pxq");* nickList.get(2)* 03. nickList.set(2, "drl");* 04. nickList.remove("phdvc");* remove(listSize-1);* nickList.size();*///01 創建ArrayList對象ArrayList<String> nickList = new ArrayList<String>();//02 往ArrayList中添加數據nickList.add("phdvb");nickList.add("phdva");boolean isChange = nickList.add("phdvb");System.out.println("ArrayList是否發生變化?"+ isChange); //ArrayList是否發生變化?trueSystem.out.println(nickList); //[phdvb, phdva, phdvb]System.out.println(nickList.get(2)); //phdvbnickList.add(1,"pxq");System.out.println(nickList); //[phdvb, pxq, phdva, phdvb]nickList.add("phdvb");nickList.add("phdvc");nickList.add("phdvc");nickList.add("phdvd");//03 更新ArrayList中的元素String beforeNick = nickList.set(2, "drl");System.out.println(beforeNick); //phdvaSystem.out.println(nickList); //[phdvb, pxq, drl, phdvb, phdvb, phdvb, phdvc, phdvd]//04 刪除ArrayList中的元素boolean isRemove = nickList.remove("phdvc");System.out.println(isRemove); //trueSystem.out.println(nickList); //僅刪除了一個元素,[phdvb, pxq, drl, phdvb, phdvb, phdvc, phdvd]int listSize = nickList.size();System.out.println(listSize); //7nickList.remove(listSize-1);System.out.println(nickList); //[phdvb, pxq, drl, phdvb, phdvb, phdvc]nickList.set(nickList.size()-2, "vb");System.out.println(nickList); //[phdvb, pxq, drl, phdvb, vb, phdvc]}
}
2.2 LinkedList
代碼實現:
public class LinkedListDemo {public static void main(String[] args) {LinkedList<String> dmList = new LinkedList<String>();dmList.add("仙逆");dmList.add("凡人");dmList.add("斗破");System.out.println(dmList); //[仙逆, 凡人, 斗破]dmList.add(0, "滄源圖");System.out.println(dmList); //[滄源圖, 仙逆, 凡人, 斗破]// 實現的是 Deque接口 中的方法dmList.addFirst("斗羅");dmList.addLast("吞噬星空");System.out.println(dmList); //[斗羅, 滄源圖, 仙逆, 凡人, 斗破, 吞噬星空]}
}
3. Set集合
3.1 概述
(1)特點
?Set集合接口間的實現關系:
(2)重要方法
代碼實現:
public class HashSetDemo {public static void main(String[] args) {// 實例化一個 Set集合Set<String> gameSet = new HashSet<String>();gameSet.add("夏洛特");gameSet.add("貂蟬");gameSet.add("戈雅");gameSet.add("不知火舞");System.out.println(gameSet); //[不知火舞, 戈雅, 夏洛特, 貂蟬]// add()返回值代表是否真正在集合中插入元素boolean isChanged = gameSet.add("米萊迪");System.out.println(gameSet); //[不知火舞, 戈雅, 夏洛特, 貂蟬, 米萊迪]System.out.println(isChanged); //trueisChanged = gameSet.add("貂蟬");System.out.println(gameSet); // [不知火舞, 戈雅, 夏洛特, 貂蟬, 米萊迪]System.out.println(isChanged); // false// Set 可以 使用所有 Collection 接口定義方法int size = gameSet.size();System.out.println(size); // 5boolean isContain = gameSet.contains("夏洛特");System.out.println(isContain); // true}
}
(3)Set集合的唯一性(hashCode() -> equals())
/*** Q1 : Set集合如何確保數據的 唯一性*//*** A1 : Set集合在新增數據時, 先會判斷hashCode() 是否已存在* 若新增的hashCode() 在Set集合中存在, 在調用equals () 進行 值比較;* 新增的hashCode() 與 equals() 都存在的情況下* Set集合認為數據已存在,不予新增*/
/*** Q2: 直接使用equals()判斷不行嗎?*//*** A2: 出于執行效率老驢* hashCode() 返回的整數結果 決定了其將Set集合中的存放位置* 由于相比于Equals()方法hashCode()計算速度會很快, 但是有可能發生哈希碰撞* 所以equals再次會發生哈希碰撞的值進行比較*/
School類(重寫了hashCode()、equals()、toString())
public class School {private String name;private String addr;public School(String name, String addr) {setAddr(addr);setName(name);}public String getAddr() {return addr;}public void setAddr(String addr) {this.addr = addr;}public String getName() {return name;}public void setName(String name) {this.name = name;}// 重寫Object類的 toString()方法@Overridepublic String toString() {return this.hashCode() + "= School{" +"name='" + name + '\'' +"addr='" + addr + '\'' +"}";}@Overridepublic int hashCode() {
// return super.hashCode();return this.name.hashCode();}@Overridepublic boolean equals(Object obj) {
// return super.equals(obj);if(obj instanceof School){School school = (School)obj;if(this.name.equals(((School)obj).getName())){return true;}else{return false;}}else{return false;}}}
Test類
public class SetConsistent {public static void main(String[] args) {String sa = "西交大";String sb = "西工大";System.out.println("sa.hashCode():" + sa.hashCode() +",sa.hashCode():" + sb.hashCode());// sa.hashCode():34473154,sa.hashCode():34594209HashSet<School> schoolHashSet = new HashSet<School>();schoolHashSet.add(new School(sa,"西安"));schoolHashSet.add(new School(sb,"西安"));schoolHashSet.add(new School("克職","克拉瑪依"));schoolHashSet.add(new School("克職","克拉瑪依"));System.out.println(schoolHashSet);//[1956725890= School{name='克職'addr='克拉瑪依'},// 1163157884= School{name='西工大'addr='西安'},// 460141958= School{name='西交大'addr='西安'}]}
}
3.2 HashSet
數據存放實例:
3.3 LinkedHashSet
數據存放示例:
代碼演示:
public class LinkedHashSetDemo {public static void main(String[] args) {Set<String> langSet= new LinkedHashSet<String>();langSet.add("Java");langSet.add("Python");langSet.add("C#");langSet.add("C++");System.out.println(langSet); //[Java, Python, C#, C++]}
}
3.4 TreeSet
code01:
public class TreeSetDemo {public static void main(String[] args) {Set<Integer> tSet = new TreeSet<Integer>();tSet.add(108);tSet.add(139);tSet.add(75);tSet.add(64);tSet.add(225);System.out.println(tSet); //[64, 75, 108, 139, 225]TreeSetDemo td = new TreeSetDemo();td.sort(); //[226, 140, 109, 76, 65]}// 重寫Comparator接口中的compare方法, 實現自定義比較邏輯class IntegerComparator implements Comparator<Integer> {public int compare(Integer o1, Integer o2) {return o2 -o1;}}public void sort(){Set<Integer> tSet = new TreeSet<Integer>(new IntegerComparator());tSet.add(109);tSet.add(140);tSet.add(76);tSet.add(65);tSet.add(226);System.out.println(tSet); //[226, 140, 109, 76, 65]}
}
4.Map
4.1?概述
4.1.1 特點 & 繼承關系
4.1.2 遍歷集合的三種方式
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;public class LoopMapThreeWays {// 遍歷集合//方式1: 增強for循環public void doForLoop(Map map){Set<String> keys = map.keySet();for(String key : keys){System.out.println(key + ":" + map.get(key));}}// 方式2: lambda 表達式public void doForLoop2(Map map){map.forEach((key, value) ->{System.out.println(key + ":" + value);});}// 方式3: 使用迭代器public void doForLoop3(Map map){Iterator<Map.Entry<String, Object>> itr = map.entrySet().iterator();while(itr.hasNext()){Map.Entry<String, Object> entry = itr.next();System.out.println(entry.getKey() + ":" + entry.getValue());}}public static void main(String[] args) {Map<String, Object> xlt = new LinkedHashMap<>();xlt.put("name", "夏洛特");xlt.put("nick", "玫瑰劍士");xlt.put("技能", "七星光芒劍");xlt.put("技能", "七星光芒斬");xlt.put("皮膚1", "浮生王");xlt.put("皮膚2", "金色皮");System.out.println(xlt);
//{name=夏洛特, nick=玫瑰劍士, 技能=七星光芒斬, 皮膚1=浮生王, 皮膚2=金色皮}LoopMapThreeWays lm = new LoopMapThreeWays();lm.doForLoop(xlt);System.out.println("——————————————————————————————————————————");lm.doForLoop2(xlt);System.out.println("——————————————————————————————————————————");lm.doForLoop3(xlt);/*name:夏洛特nick:玫瑰劍士技能:七星光芒斬皮膚1:浮生王皮膚2:金色皮*/}
}
4.2 HashMap
code:
import java.util.HashMap;
import java.util.Map;public class HashMapDemo {public static void main(String[] args) {Map<String, Object> xlt = new HashMap<String, Object>();xlt.put("name", "夏洛特");xlt.put("nick", "玫瑰劍士");xlt.put("技能", "七星光芒劍");xlt.put("技能", "七星光芒斬");System.out.println(xlt); //{nick=玫瑰劍士, 技能=七星光芒斬, name=夏洛特}String heroNick = (String) xlt.get("nick");System.out.println(heroNick); //玫瑰劍士System.out.println(xlt.containsKey("技能")); //trueSystem.out.println(xlt.containsKey("皮膚")); //falsexlt.put("皮膚1", "浮生王");int count = xlt.size();System.out.println(count); //4xlt.put("皮膚2", "金色皮");System.out.println(xlt); //{nick=玫瑰劍士, 技能=七星光芒斬, 皮膚2=金色皮, 皮膚1=浮生王, name=夏洛特}String removeValur = (String)xlt.remove("皮膚2");System.out.println(removeValur); //金色皮}
}
4.3 LinkedHashMap
public class LinkedHashMapDemo {public static void main(String[] args) {Map<String, Object> xlt = new LinkedHashMap<>();xlt.put("name", "夏洛特");xlt.put("nick", "玫瑰劍士");xlt.put("技能", "七星光芒劍");xlt.put("技能", "七星光芒斬");xlt.put("皮膚1", "浮生王");xlt.put("皮膚2", "金色皮");System.out.println(xlt);
//{name=夏洛特, nick=玫瑰劍士, 技能=七星光芒斬, 皮膚1=浮生王, 皮膚2=金色皮}}
}
4.4 TreeMap
import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;public class TreeMapDemo {public static void main(String[] args) {/*正常需求測試1:*/Map<Object, Object> tMap = new TreeMap<Object, Object>();tMap.put("a2", 589);tMap.put("a1", "vb");tMap.put("b4", "運還是重要的");tMap.put("b5", "自信也重要");tMap.put("b2", 3.5);System.out.println(tMap);
//{a1=vb, a2=589, b2=3.5, b4=運還是重要的, b5=自信也重要}/*比較方法重寫測試2:*/TreeMapDemo td = new TreeMapDemo();td.sort(); //{b5=自信也重要, b4=運還是重要的, b2=3.5, a2=589, a1=vb}}class tMapComparator implements Comparator<String> {@Overridepublic int compare(String o1, String o2) {return o2.compareTo(o1);}}public void sort(){Map<String, Object> t2Map = new TreeMap<>(new tMapComparator());t2Map.put("a2", 589);t2Map.put("a1", "vb");t2Map.put("b4", "運還是重要的");t2Map.put("b5", "自信也重要");t2Map.put("b2", 3.5);System.out.println(t2Map);}
}