集合（Collection、Map）

Collection集合

List集合

//List循环遍历
import java.util.ArrayList;import java.util.Iterator;
import java.util.List;public class Pratice04 {public static <E> void main(String[] args) {List<Worker> list = new ArrayList<Worker>();list.add(new Worker("zhang3", 18, 3000.0));list.add(new Worker("li4", 25, 3500.0));list.add(new Worker("li4", 25, 3500.0));list.add(new Worker("wang5", 22, 3200.0));list.add(new Worker("wang5", 22, 3200.0));//2)在li4之前插入一个工人，信息为：姓名：zhao6，年龄：24，工资3300list.add(1, new Worker("zhao6", 24, 3600.0));for (Worker worker : list) {System.out.println(worker);}System.out.println("=====================");//3)删除wang5的信息list.remove(3);//4利用for循环遍历,打印List中所有工人的信息for (Worker worker : list) {System.out.println(worker);}System.out.println("=====================");//方法二：for (Iterator<Worker> it = list.iterator(); it.hasNext(); System.out.println(it.next()));System.out.println("=====================");//利用迭代遍历，对List中所有的工人调用work方法。Iterator<Worker> iterator = list.iterator();while (iterator.hasNext()) {Worker w = iterator.next();w.work();}for (Worker worker : list) {worker.work();}}
}class Worker {private String name;private Integer age;private Double salary;public Worker() {super();}public Worker(String name, Integer age, Double salary) {super();this.name = name;this.age = age;this.salary = salary;}public void work() {System.out.println("奋斗！");}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public Double getSalary() {return salary;}public void setSalary(Double salary) {this.salary = salary;}@Overridepublic String toString() {return "Worker [name=" + name + ", age=" + age + ", salary=" + salary + "]";}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + ((age == null) ? 0 : age.hashCode());result = prime * result + ((name == null) ? 0 : name.hashCode());result = prime * result + ((salary == null) ? 0 : salary.hashCode());return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;Worker other = (Worker) obj;if (age == null) {if (other.age != null)return false;} else if (!age.equals(other.age))return false;if (name == null) {if (other.name != null)return false;} else if (!name.equals(other.name))return false;if (salary == null) {if (other.salary != null)return false;} else if (!salary.equals(other.salary))return false;return true;}}//List去除重复元素
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.ListIterator;public class Pratice05 {public static <E> void main(String[] args) {List<Worker> list = new ArrayList<Worker>();list.add(new Worker("zhang3", 18, 3000.0));list.add(new Worker("li4", 25, 3500.0));list.add(new Worker("li4", 25, 3500.0));list.add(new Worker("wang5", 22, 3200.0));list.add(new Worker("wang5", 22, 3200.0));//去除重复元素（普通for,迭代器，集合都要重写equals方法）//方法一：普通for(选择排序思想==选择对比去重) for (int i = 0; i < list.size() - 1; i++) {for (int j = 1 + i; j < list.size(); j++) {if (list.get(i).equals(list.get(j))) {list.remove(j);j--;}}}System.out.println(list);//方法三：迭代器ListIterator<Worker> lis = list.listIterator();ArrayList<Worker> newlist = new ArrayList<Worker>();while (lis.hasNext()) {Worker w = lis.next();if (!newlist.contains(w)) {newlist.add(w);}}list = newlist;System.out.println(list);//方法四 :创建新集合，forArrayList<Worker> newlist2 = new ArrayList<Worker>();for (Worker worker : list) {if (!newlist2.contains(worker)) {newlist2.add(worker);}}list = newlist2;System.out.println(list);//方法二：利用hashset去除重复元素（重写equals方法）removeDuplist(list);System.out.println(list);}public static List<Worker> removeDuplist(List<Worker> list) {HashSet<Worker> hs = new HashSet<Worker>(list);list.clear();list.addAll(hs);return list;}}

Set集合

//TreeSet比较排序
import java.util.Comparator;
import java.util.TreeSet;//键盘录入5个学生信息(姓名,年龄，语文成绩,数学成绩,英语成绩),按照总分从高到低输出到控制台
//注：总分相同等情况下按照语文成绩排序，其次是数学成绩、英语成绩、年龄、姓名
public class Pratice08 {public static void main(String[] args) {TreeSet<Students> ts = new TreeSet<>(new Comparator<Students>() {@Overridepublic int compare(Students s1, Students s2) {double cmp = s2.getSumScore() - s1.getSumScore();double cmp2 = (cmp == 0) ?                    s2.getChineseScore().compareTo(s1.getChineseScore()) : cmp;double cmp3 = (cmp2 == 0) ? s2.getMathScore().compareTo(s1.getMathScore()) : cmp2;double cmp4 = (cmp3 == 0) ? s2.getEnglishScore().compareTo(s1.getEnglishScore()) : cmp3;double cmp5 = (cmp4 == 0) ? s2.getAge().compareTo(s1.getAge()) : cmp4;double cmp6 = (cmp5 == 0) ? s1.getName().compareTo(s2.getName()) : cmp5;return cmp6 < 0 ? -1 : (cmp6 == 0 ? 0 : 1);}});for (int i = 0; i < 20; i++) {String name = (char) (i + 97) + "Mr";Integer age = getRandom(20, 22);double chineseScore = getRandom(80, 82);double mathScore = getRandom(84, 87);double englishScore = getRandom(87, 89);Students s = new Students(name, age, chineseScore, mathScore, englishScore);ts.add(s);}for (Students s : ts) {System.out.println(s);}}public static int getRandom(int start, int end) {return (int) (Math.random() * (end - start + 1) + start);}
}class Students {private String name;private Integer age;private Double chineseScore;private Double mathScore;private Double englishScore;public Students() {super();}public Students(String name, Integer age, Double chineseScore, Double mathScore, Double englishScore) {super();this.name = name;this.age = age;this.chineseScore = chineseScore;this.mathScore = mathScore;this.englishScore = englishScore;}@Overridepublic String toString() {return "Students [name=" + name + ", age=" + age + ", chineseScore=" + chineseScore + ", mathScore=" + mathScore+ ", englishScore=" + englishScore + ", getSumScore()=" + getSumScore() + "]";}public Double getSumScore() {Double sumScore = chineseScore + mathScore + englishScore;return sumScore;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public Double getChineseScore() {return chineseScore;}public void setChineseScore(Double chineseScore) {this.chineseScore = chineseScore;}public Double getMathScore() {return mathScore;}public void setMathScore(Double mathScore) {this.mathScore = mathScore;}public Double getEnglishScore() {return englishScore;}public void setEnglishScore(Double englishScore) {this.englishScore = englishScore;}}

Map集合

//Map集合遍历
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;/** 1、使用HashMap类实例化一个Map类型的对象m1，键（String类型）和值（Integer型）分别用于存储员工的姓名和工资，存入数据如下：张三——800元；李四——1500元；王五——3000元；1）将张三的工资更改为2600元2）为所有员工工资加薪100元；3）遍历集合中所有的员工4）遍历集合中所有的工资试试将键改写成Employee*/public class Demo01 {public static void main(String[] args) {Map<String, Integer> m = new HashMap<String, Integer>();m.put("张三", 800);m.put("李四", 1500);m.put("王五", 3000);//1.将张三的工资更改为2600元m.put("张三", 2600);System.out.println(m);//2.为所有员工工资加薪100元；//获取所有键（员工）的集合Set<String> keys = m.keySet();//通过键修改值for (String name : keys) {m.put(name, m.get(name) + 100);}System.out.println(m);//3）遍历集合中所有的员工Set<String> keySet = m.keySet();for (String name : keySet) {System.out.println(name);}//4）遍历集合中所有的工资Collection<Integer> values = m.values();for (Integer salary : values) {System.out.println(salary);}System.out.println("==========================");//5.遍历集合//1)迭代器遍历Iterator<String> it = m.keySet().iterator();while (it.hasNext()) {String key = it.next();Integer salary = m.get(key);System.out.println(key + "|" + salary);}System.out.println("==========================");//2)for遍历(通过遍历键集合得到每一个键和对应的值)for (String key : m.keySet()) {System.out.println(key + "|" + m.get(key));}System.out.println("==========================");//3)通过map的entry方法获取键值对（for）Set<Entry<String, Integer>> keyValues = m.entrySet();for (Entry<String, Integer> keyValue : keyValues) {String key = keyValue.getKey();Integer value = keyValue.getValue();System.out.println(key + "|" + value);}System.out.println("==========================");//4)通过map的entry方法获取键值对（while：用迭代器）Iterator<Entry<String, Integer>> iterator = m.entrySet().iterator();while (iterator.hasNext()) {Entry<String, Integer> keyValue = iterator.next();String key = keyValue.getKey();Integer value = keyValue.getValue();System.out.println(key + "|" + value);}}
}

//TreeMap比较排序
import java.util.Comparator;
import java.util.TreeMap;public class TreeMapDemo02 {public static void main(String[] args) {TreeMap<Employee, Double> tm = new TreeMap<>(new Comparator<Employee>() {@Overridepublic int compare(Employee e1, Employee e2) {double cmp = e1.getSalary() - e2.getSalary();double cmp2 = (cmp == 0) ? e1.getId().compareTo(e2.getId()) : cmp;double cmp3 = (cmp2 == 0) ? e1.getName().compareTo(e2.getName()) : cmp2;return cmp3 > 0 ? 1: (cmp < 0 ? -1 : 0);}});tm.put(new Employee("1001", "zhangsan", 8000.0), 8000.0);tm.put(new Employee("1002", "lisi", 8000.0), 8000.0);tm.put(new Employee("1001", "haha", 8000.0), 8000.0);tm.put(new Employee("1003", "zhangsan", 8000.0), 8000.0);tm.put(new Employee("1001", "hehe", 8000.0), 8000.0);tm.put(new Employee("1005", "zhangsan", 8000.0), 8000.0);tm.put(new Employee("1007", "zhangsan", 8000.0), 8000.0);tm.put(new Employee("1006", "zhangsan", 8000.0), 8000.0);tm.put(new Employee("1001", "zhangsan", 8000.0), 8000.0);tm.put(new Employee("1001", "zhangsan", 9000.0), 8000.0);tm.put(new Employee("1001", "zhangsan", 10000.0), 8000.0);tm.put(new Employee("1001", "zhangsan", 5000.0), 8000.0);for (Employee e : tm.keySet()) {Double salary = tm.get(e);System.out.println(e + "=" + salary);}}}

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集合（Collection、Map）

Collection集合

List集合

Set集合

Map集合

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