Java当中的集合框架Map

public String getWeek(int num){
 if(num<0 || num>7){
  throw new NoWeekException(num+"没有对应的星期");
  String[] weeks = {"","星期一"...."星期日"};
  return weeks[num];
 }
}

java.util
接口 Map<K，V>
参数：
K为此映射的键
V为此映射的值

Bindings,ConcurrentMap<K,V>,ConcurrentNavigableMap<K,V>,LogicalMessageContext,MessageContext,NavigableMap<K,V>,SOAPMessageContext,SorteMap<K,V>

AbstractMap,Attributes,AuthProvider,ConcurrentHashMap,ConcurrentSkipListMap,EnumMap,HashMap,Hashtable,IdentityHashMap,LinkedHashMap,PrinterStateReasons,Properties,Provider,RenderingHints,SimpleBindings,TabularDataSupport,TreeMap,UIDefaults,WeakHashMap

public interface Map<K,V>

V put (E key, V value)

UnsupportedOperationException：不支持put操作
ClassCastException：不允许用映射关系
NullPointerException：将指定的键或者值为null，而此映射却不允许存储
IllegalArgumentException：指定的键或者值不允许存储到映射中

java.util
类 HashMap<K,V>
java.lang.Object
 -> java.util.AbstractMap<K,V>
  -> java.util.HashMap<K,V>

K-为所对应的键
V-为所对应的值

Serializable,Cloneable,Map<K,V>

LinkedHashMap，PrinterStateReasons

public class HashMap<K,V> extends AbstractMap<K,V>
implements Map<K,V>, Cloneable, Serializable

import java.util.HashMap;
public class MapDemo {
 public static void main(String[] args){
  // 建立map
  Map<String,String> map = new HashMap<String,String>();
 // 添加元素
  map.put("星期一", "Monday");
  mpa.put( ...// 自行添加 );
  map.put("星期日", "Sunday");
  // 添加元素时，如果键相同，值会覆盖
  map.put("星期日", "SundayDemo");  // 值被覆盖
 // 获取值
 String value = map.get("星期日"); // 键存在，返回值，反之返回null，为空
 // 删除元素
 String s = map.remove("星期日"); // 删除对应的键值对关系，这样在Map集合中就少了这一对键值对
 }
}

Map<String,String> map = new HashMap<String,String>();
map.put("星期一", "Monday");
map.put("星期日", "Sunday");

Set<String> keySet = map.keySet();
for(Iterator<String> it = keySet.iterator(); it.hasNext(); ){
 String key = it.next();
 String value = map.get(key);
 System.out.println(key + " : " + value);
}

for(String key : keySet){
 System.out.println(key + " = " + map.get(key));
}

Set<Map.Entry<K,V>> entrySet()

Set<Map.Entry<String,String>> entrySet = map.entrySet();
Iterator< Map.Entry<String,String> > it = entrySet.iterator();
while(it.hasNext(K,V)){
 Map.Entry<String,String> m = it.next();
 // 获取键
 String key = m.getKey();
 // 获取值
 String value = m.getValue();
 System.out.println(key + " : " + value);
}

java.util
接口 Map.Entry<K,V>

AbstractMap.SimpleEntry , AbstractMap.SimpleImmutableEntry

public static interface Map.Entry<K,V>
// 为映射项 - 键-值 对

for(Map.Entry<String,String> m : map.entrySet()){
 String key = m.getKey();
 String value = m.getValue();
 System.out.println(key + " : " + value);
}

interface Map{
 public static interface Entry();
}

Collection<String> values = map.values();
for(String value : values){
 System.out.println("value:"+value);
}

public class HashMapDemo {
 public static void main(String[] args){
  Map<Student,String> map = new HashMap<Student,String>();
 // 添加元素
 map.put(new Student("da",12), "1");
 map.put(new Student("shu",13), "2");
 map.put(new Student("dashu",14), "3");
 // 取出数据
 // Set<Student> keySet = map.keySet();
 // for(Student key : keySet){}
 for(Student key : map.keySet() ){
  String value = map.get(key);
  System.out.println(key.toString() + " : " + value);
 }
 }
}

public class Student implements Comparable<Student>{
 private String name;
 private int age;
 public Student(){
  super();
 }
 public Student(String name, int age){
  super();
  this.name = name;
  this.age = age;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name; 
 }
 public int getAge() {
  return age;
 }
 public void setAge(int age){
  this.age = age;
 }
 @Override 
 public String toString() {
  return "Student [name = " + name +"，age = " + age + "]";
 }
 @Override
 public int hasCode() {
  final int prime = 31;
  int result = 1;
  result = prime + result + age;
  result = prime + result + ((name == null) ? 0 : name.hashCode());
  return result;
 }
 @Override
 public boolean equals(Object obj){
  if(this == obj)
   return true;
  if(obj == null)
   return false;
  if(getClass() != obj.getClass() )
   return false;
  Student other = (Student) obj;
  if(age != other.age)
   return false;
  if(name == null){
   if(other.name != null)
    return false;
  }else if(!name.equals(other.name))
    return false;
  return true;
 }
 @Override
 public int  compareTo(Student o){
  int temp = this.age - o.age;
  
  return temp == 0? this.name.compareTo(o.name) : temp;
 }
}

public class TreeMapDemo{
 public static void main(String[] args){
   Map<Student, String> map = new TreeMap<Student, String>(new ComparatorByName());
 // 添加元素
 map.put(new Student("da",12), "1");
 map.put(new Student("shu",13), "2");
 map.put(new Student("dashu",14), "3");
 // 取出数据
 for(Map.Entry<String,String> m : map.entrySet()){
  Student key = m.getKey();
  String value = m.getValue();
  System.out.println(key + " : " + value);
 }
 }
}

public class ComparatorByName implements Comparator<Student>{
 @Override
 public int compare(Student o1, Student o2){
  int temp = o1.getName().compareTo(o2.getName());
  return temp == 0 ? o1.getAge() - o2.getAge() : temp;
 }
}

public class CollectionsDemo {
   public static void main(String[] args) {
      Map m = new HashMap(); 
      m.put("da", "8");
      m.put("shu", "9");
      m.put("dashu", "10");
      m.put("dashucoding", "12");
      System.out.println(m);
   }
}

Iterator keyValues = map.entrySet().iterator();
Iterator keys = map.keySet().iterator();
Iterator values = map.values().iterator();