Java容器---Map基础

  1 public class MapDemo {
  2 
  3 	/**
  4 	 * @param args
  5 	 */
  6 	public static void main(String[] args) {
  7 
  8 		Map<Integer,String> map = new HashMap<Integer,String>();
  9 		methodDemo(map);
 10 		/*
 11 		 * 需求:Map集合中存储学号，姓名。
 12 		 */
 13 	}
 14 	public static void methodDemo(Map<Integer,String> map){
 15 
 16 		//1，存储键值对。如果键相同，会出现值覆盖。
 17 		System.out.println(map.put(3, "xiaoqiang"));
 18 		System.out.println(map.put(3, "erhu"));
 19 		map.put(7, "wangcai");
 20 		map.put(2, "daniu");
 21 
 22 //		System.out.println(map.remove(7));
 23 
 24 		System.out.println(map.get(7));
 25 
 26 		System.out.println(map);
 27 	}
 28 }

  1 public class MapTest {
  2 
  3 	/**
  4 	 * @param args
  5 	 */
  6 	public static void main(String[] args) {
  7 
  8 		/*
  9 		 * 什么时候使用map集合呢？
 10 		 * 当需求中出现映射关系时，应该最先想到map集合。
 11 		 *
 12 		 */
 13 
 14 		String cnWeek = getCnWeek(3);
 15 		System.out.println(cnWeek);
 16 		String enWeek = getEnWeek("星期八");
 17 		System.out.println(enWeek);
 18 
 19 	}
 20 	//根据中文星期，获取对应的英文星期。
 21 	//中文与英文相对应，可以建立表，没有有序的编号，只能通过map集合。
 22 	public static String getEnWeek(String cnWeek){
 23 
 24 		//创建一个表。
 25 		Map<String,String> map = new HashMap<String,String>();
 26 		map.put("星期一","Monday");
 27 		map.put("星期二","Tuesday");
 28 		map.put("星期三","Wednesday");
 29 		map.put("星期四","Thursday");
 30 		map.put("星期五","Friday");
 31 		map.put("星期六","Saturday");
 32 		map.put("星期日","Sunday");
 33 
 34 
 35 		return map.get(cnWeek);
 36 
 37 	}
 38 
 39 	/**
 40 	 * 根据用户的指定的数据获取对应的星期。
 41 	 */
 42 	public static String getCnWeek(int num){
 43 
 44 		if(num<=0 || num>7){
 45 			throw new NoWeekException(num+",没有对应的星期");
 46 		}
 47 
 48 		String[] cnWeeks = {"","星期一","星期二","星期三","星期四","星期五","星期六","星期日"};
 49 
 50 		return cnWeeks[num];
 51 
 52 	}
 53 
 54 }
 55 

  1 public class Employee implements Comparable<Employee> {
  2 
  3 	private String name;
  4 	private int age;
  5 
  6 
  7 	public Employee() {
  8 		super();
  9 
 10 	}
 11 
 12 	public Employee(String name, int age) {
 13 		super();
 14 		this.name = name;
 15 		this.age = age;
 16 	}
 17 
 18 	public String getName() {
 19 		return name;
 20 	}
 21 	public void setName(String name) {
 22 		this.name = name;
 23 	}
 24 	public int getAge() {
 25 		return age;
 26 	}
 27 	public void setAge(int age) {
 28 		this.age = age;
 29 	}
 30 
 31 	@Override
 32 	public String toString() {
 33 		return "Emplooye [name=" + name + ", age=" + age + "]";
 34 	}
 35 
 36 	@Override
 37 	public int hashCode() {
 38 		final int prime = 31;
 39 		int result = 1;
 40 		result = prime * result + age;
 41 		result = prime * result + ((name == null) ? 0 : name.hashCode());
 42 		return result;
 43 	}
 44 
 45 	@Override
 46 	public boolean equals(Object obj) {
 47 		if (this == obj)
 48 			return true;
 49 		if (obj == null)
 50 			return false;
 51 		if (getClass() != obj.getClass())
 52 			return false;
 53 		Employee other = (Employee) obj;
 54 		if (age != other.age)
 55 			return false;
 56 		if (name == null) {
 57 			if (other.name != null)
 58 				return false;
 59 		} else if (!name.equals(other.name))
 60 			return false;
 61 		return true;
 62 	}
 63 
 64 	@Override
 65 	public int compareTo(Employee o) {
 66 
 67 		int temp = this.age - o.age;
 68 		return temp==0? this.name.compareTo(o.name):temp;
 69 	}
 70 
 71 }
 72 
 73 ///////////////////////////////////////////////////////////////////////////////////////////
 74 public class HashMapTest {
 75 
 76 	/**
 77 	 * @param args
 78 	 */
 79 	public static void main(String[] args) {
 80 		/*
 81 		 * 1， 将员工和归属存储到HashMap集合中并取出。 同姓名同年龄视为同一个学生。
 82 		 */
 83 
 84 
 85 		Map<Employee,String>  map = new HashMap<Employee,String>();//如果改成LinkedHashMap可以实现有序。
 86 
 87 		map.put(new Employee("xiaozhang",24),"北京");
 88 		map.put(new Employee("laoli",34),"上海");
 89 		map.put(new Employee("mingming",26),"南京");
 90 		map.put(new Employee("xili",30),"广州");
 91 		map.put(new Employee("laoli",34),"铁岭");
 92 
 93 		Set<Employee> keySet = map.keySet();
 94 		for(Employee employee : keySet){
 95 
 96 			String value = map.get(employee);
 97 
 98 			System.out.println(employee.getName()+":"+employee.getAge()+"...."+value);
 99 
100 
101 		}
102 
103 //		for(Employee employee : map.keySet()){
104 //			
105 //		}
106 
107 
108 	}
109 
110 
111 
112 }
113 

  1 public class TreeMapTest {
  2 
  3 	/**
  4 	 * @param args
  5 	 */
  6 	public static void main(String[] args) {
  7 
  8 		/*
  9 		 * 2， 按照学生的年龄进行升序排序并取出。 按照学生的姓名进行升序排序并取出。
 10 		 */
 11 
 12 		// 自定义比较器。
 13 		Comparator<Employee> comparator = new Comparator<Employee>() {
 14 
 15 			@Override
 16 			public int compare(Employee o1, Employee o2) {
 17 
 18 				int temp = o1.getName().compareTo(o2.getName());
 19 				return temp == 0 ? o1.getAge() - o2.getAge() : temp;
 20 			}
 21 		};
 22 
 23 		Map<Employee, String> map = new TreeMap<Employee, String>(comparator);
 24 
 25 		map.put(new Employee("xiaozhang", 24), "北京");
 26 		map.put(new Employee("laoli", 34), "上海");
 27 		map.put(new Employee("mingming", 26), "南京");
 28 		map.put(new Employee("xili", 30), "广州");
 29 		map.put(new Employee("laoli", 34), "铁岭");
 30 
 31 		// entrySet
 32 		Set<Map.Entry<Employee, String>> entrySet = map.entrySet();
 33 		for (Map.Entry<Employee, String> me : entrySet) {
 34 
 35 			Employee key = me.getKey();
 36 			String value = me.getValue();
 37 			System.out.println(key.getName() + "::" + key.getAge() + "....."
 38 					+ value);
 39 		}
 40 
 41 	}
 42 
 43 }
 44 

2018-01-07

内容主要来自API