黑马程序员——HashMap综合练习

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package map;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
public class HashCode_equals {
 public static void main(String[] args) {
  HashMap<Student,String> map=new HashMap<Student,String>();
  map.put(new Student("张三",22),"北京");
  map.put(new Student("李四",212),"北京");
  map.put(new Student("李四",212),"北京fff");//注意：健一样，再插入，会覆盖之前的值
  map.put(new Student("王五",233),"上海");
  map.put(new Student("赵六",2332),"上海");
  map.put(new Student("风气",2662),"广州");
  //第一种取值方式
  Set<Student> set=map.keySet();
  Iterator<Student> iter=set.iterator();
  while(iter.hasNext()){
   Student stu=iter.next();
   System.out.println(stu.toString() +",address:"+map.get(stu));//因为复写了这个方法，所以可以从这里取name和age
  }//Student.toString(),方法不写的话，也会自动调用的啊
  System.out.println("--------------------------------------------------------------");
  //第二种取值方式
  Set<Map.Entry<Student,String>> set2=map.entrySet();
  Iterator<Map.Entry<Student,String>> iter2=set2.iterator();
  while(iter2.hasNext()){
   Map.Entry<Student,String> entry=iter2.next();
   Student stu=entry.getKey();
   String str=entry.getValue();
   System.out.println(stu +",address:"+str);//因为复写了这个方法，所以可以从这里取name和age
  }//Student.toString(),方法不写的话，也会自动调用的啊
 System.out.println("============================================================");
  //按默认排序从小到大
  TreeMap<Student,String> ts=new TreeMap<Student,String> (new MyComparetor());//定义一个比较器，有比较器，按比较器的规则进行比较
  ts.put(new Student("aa张三",254542),"北京");
  ts.put(new Student("aa张三",212),"北京");
  ts.put(new Student("ac李四",212),"北京fff");//注意：健一样，再插入，会覆盖之前的值
  ts.put(new Student("dd王五",233),"上海");
  ts.put(new Student("ee赵六",2332),"上海");
  ts.put(new Student("ea风气",2662),"广州rewqrew");
  
  Set<Map.Entry<Student,String>> treemap=ts.entrySet();
  Iterator<Map.Entry<Student,String>> iter_tree=treemap.iterator();
  while(iter_tree.hasNext()){
   Map.Entry<Student,String> tree_map=iter_tree.next();
   System.out.println(tree_map.getKey()+"----address:"+tree_map.getValue());
  }
  
 }
}
class MyComparetor implements Comparator<Student>{
 public int compare(Student stu1, Student stu2) {
  int num=stu1.getName().compareTo(stu2.getName());//线比较姓名
  if(num==0){//姓名相同，在比较年龄
   return new Integer(stu1.getAge()).compareTo(new Integer(stu2.getAge()));
  }
  return num;
 }
}
/**
 * 一：复写hashCode()方法和equals()方法是为了此对象存入Hash结构中定义的新的存入规则
 * 二：实现Comparator接口，是为了此对象存入二叉树中定义的新的存入规则
 * @author wjw
 *
 */
class Student implements Comparable<Student>{
 private String name;
 private int age;
 public Student(String name,int age){
  this.name=name;
  this.age=age;
 }
 //实现接口中的方法
 public int compareTo(Student stu) {
  int num=new Integer(this.age).compareTo(stu.age);//先按照年龄排序
  if(num==0){//如果年龄相等
   return this.name.compareTo(stu.name);//再按照姓名排序
  }
  return num;
 }
 /
 //从新定义hashCode()方法
 public int hashCode(){
  return this.name.hashCode()+this.age*43;//返回自定义的hashCode值
 }
 //从新定义equals()方法
 public boolean equals(Object obj){
  if(!(obj instanceof Student)){//判断，obj向下转型不是Student类的话，抛出异常
   throw new ClassCastException("类型不匹配");
  }
  Student s=(Student)obj;
  return this.name.equals(s.name)&&this.age==s.age;
 }
 //复写Object类中的toString()方法
 public String toString(){
  return "name:"+this.name+",age:"+this.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;
 }
 
}

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