HashMap的应用
package zxd.work619;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class BookTest {
public static void main(String[] args) {
Book book1 = new Book("八仙过海", "200");
Book book2 = new Book("西游记", "500");
Book book3 = new Book("东游记", "400");
Map<String, Book> map = new HashMap<String, Book>();//创建集合
map.put("1", book1);
map.put("2", book2);
map.put("3", book3);
Set<String> set = map.keySet();
for (String s : map.keySet()) {
System.out.println(map.get(s));
}
//遍历一
for (Book st : map.values()) {
System.out.println();
}
//遍历二
for (Map.Entry<String, Book> book : map.entrySet()) {
System.out.println(book.getKey()+","+book.getValue());
}
//遍历三
Iterator i = map.entrySet().iterator();//迭代器的调用
while(i.hasNext()){
Map.Entry<Student, Book> m = (Map.Entry<Student, Book>)i.next();
System.out.println(m);
}
}
}
速度快慢:遍历三 > 遍历二 > 遍历一
输出结果:
3=Students [name=张三, age=22] 2=Students [name=张二, age=21] 1=Students [name=张一, age=20] 5=Students [name=张五, age=24] 4=Students [name=张四, age=23]